Java Tutorial

Switch Statement

The Switch Statement permits the variables to be tested for equal opportunity against the set of values. All Values are called the case, and the variable that is going to be switched on is verified for each case.

Rules that are applied to the Switch Statement

• A Variable is used in the Switch statement that can be strings, integers, enums, and Convertible integers like (byte, char, short) 
• The value for the case should be the same as the data type just like a variable in the switch and it should be literal or a constant.  
• It is possible that one can have more case statements within the switch. All the case is followed by a value that can be compared to and to the colon. 
• In case the break statement is reached, then it's switch terminates the control flow hops to next line that supersedes a switch statement 
• In case when a variable is switched to the equal case and the statements which follow the case would execute continuously till the break statement is being reached. 
• The Switch statement shall consist of an optional default case, that should appear at the end of a switch. A default case could be used in performing the task when no single case is true. The break is not required in a default case. 
• It is not mandatory that all the cases are required to have a break. If at all there are no break cases found, then the flow of control falls through the subsequent cases till the break is reached. 

For Example

Output

Java Numbers

Usually, when you work with Numbers, you can use the primitive data types namely long, double, byte, and int.

Anyhow, in the development, you can come across circumstances where you must use the objects rather than primitive data types. To reach this, Java provides the Wrapper Classes.

The Wrapper Classes ( Long, Byte, Double, Float, Integer, and Short) are the different subclasses of an abstract class number.

An Object is the Wrapper Class that consists of Wraps and its corresponding primitive data types. For converting the primitive data types to objects it is called boxing and it is to be looked after by a compiler.

Hence, while using the Wrapper class you should pass the value of a primitive data type for the constructor of a Wrapper Class.

Now, the Wrapper Object shall be converted to a primitive data type and this practice is known as unboxing. The Number Class is a unit of java.lang package.

The different types of Numbers in Java are

When b is designated as the integer value, and now the compiler boxes the integer as b is the integer object. Further, b is now unboxed so it can be added as an integer.

Number Methods

In this Java Tutorial for Beginners let us go through the instance methods and all the subclasses which a Number class implements

Java Characters

Usually, whenever you work with the characters, you can use the data types char.

For Example

In the development, you can come across the situation where you should use the objects rather than the primitive data types. To reach this, Java gives the wrapper class character of a primitive data type char. This character class provides a more useful class i.e (static methods) to manipulate the characters. Then, you can build the Character object within a Character constructor.

Character ch = new Character('a');

A Java Compiler can create the Characters of the Object for you in certain circumstances. For instance, in case if you pass the primitive char into the method that seeks an object, then the compiler immediately converts the char to the Character for you. It is called autoboxing or unboxing in case the conversion turns the other way.

Escape Sequences

The character that is anticipated by the backslash (\) is the escape sequence and it consists of unique meaning to a compiler.

The below table clearly depicts the Java Escape sequences:

The different Character Methods are:

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Java Strings

The Strings are used for stacking shorter text.

The String Variable consists of the compilation of characters that are bounded by the double quotes:

Example

We can build the variable type of string and assign them to the value

Create the variable of type String and assign it a value:

String Length

The String Length in Java is the object that consists of the methods which can exhibit operations on the strings. For instance, the length of the string is found with a length() method:

More String Methods

More string methods are found and they are toLowerCase() and toUpperCase().

To identify a Character in the String

An indexOf() method send back the index (the exact position) of the first occurrence of the described text in the string (inclusive of the whitespace):

Java Notes for Beginners:

Java usually counts a position from zero So,

• 0 is the 1st position 
• 1 is the 2nd position 
• 2 is the 3rd position and so on... 

String Concatenation

The Operators could be used between the strings for combining them and it is called concatenation.

Java Notes for Beginners:

We have inserted an empty text (" ") for developing the space between the First & Last Name on the print.

Further, you can also use a contact() method for concentrating the two strings

Special Characters

As it is important that the strings should be written within a quote since Java would misinterpret this as the string and provoke the error:

The best solution for avoiding a problem is by using a backslash escape character.

A backslash (\) escape character help in modifying the special characters into the string characters:

A sequence \" adds the double quote to the string:

The sequence \' aids in adding the single quote in the string

The sequence \\ helps in inserting the single backslash to a string:

This \\ sequence adds a single backslash to a string:

This \\ sequence adds a single backslash to a string:

Java Notes for Beginners:

It utilizes the + operator for concatenation & addition. The Numbers are added and the strings are concatenated.

When you add to numbers, the outcome will be a number

When you add the 2 strings, the outcome will be the string concatenation:

Java Arrays

Generally, Java enables a Data Structure, an array, that stacks in the fixed-size of the consecutive elements of similar kinds. The Arrays are used for storing the acquisition of data and it is useful to consider that an array as the compilation of variables of the same types. Rather than declaring the individual variables like number0, number99.... and so on, you can declare 1 array variable like numbers and utilize number[0], a number[99]... and so to interpret the individual variables.

In this Java Programming Tutorial, we will make you understand how to create the arrays, declare the array variables, and the process of arrays that are used in indexing the variables.

For creating an Array

It is possible to create the array using a new operator by following the syntax-

Syntax

The above statement helps in two things

Creates the array utilizing a new dataType[arraySize] It designates the reference of a newly created array and the variable of the arrayRefVar.

You can create, declare, and assign the reference of an array to a variable and can be merged into one statement as given below

Processing Arrays

At the time of Processing the array elements, you can either use the foreach or a for a loop as all the elements in the array are of a similar type and the size of an array is known.

The Foreach Loop

JDK 1.5 popularized the new for loop that is known as enhanced for loop or foreach loop that allows you to pass through the entire array orderly without using the index variable.

Passing the Arrays to the Methods

Just like how you pass on the primitive type of values to the methods, also you could pass the arrays to the methods.

You can call the above by passing the array. For instance, the following statement calls the print array method for displaying 5,7,2,8,9 and 2-

Java Date and Time

Java supports the Date class that is available in java. util package, this class encloses the current time and date.

A Date Class hold two constructors as given below

Below are the methods of Data Class

Get the Current Date & Time

It is the easiest method for accessing the current Date & Time in Java. You can make use of the simple Date object along with the toString() method for printing the current date & time as given below:

Date Comparison

Mentioned below are the three different types for comparing two dates

• You can use the following methods before (), equals(), and after(). As the 12th month comes prior to the 18th for instance the new date ( 95, 3,12). Before (new date 95,3,18) returns true. 
• You can also use the getTime() for knowing the total number of milliseconds that have passed by since January 1, 1970 midnight for both the objects and you can compare these values. 
• You can also use the compareTo() form, which is characterized by the implemented Date and Comparable interface.  

Date Formatting Using a SimpleDate Format

The SimpleDateFormat is the concrete class that is applied for parsing and formatting the dates in a locale-sensitive manner. A SimpleDateFormat permits you to begin by selecting any user-defined patterns for the date-time formatting.

Time DateFormat Codes

If you need to specify a time format, then you can use the time pattern string. When using this template, all the ASCII letters are reserved as the pattern letters and it is termed as following:

Date Formatting Using a SimpleDate Format

The SimpleDateFormat is the concrete class that is applied for parsing and formatting the dates in a locale-sensitive manner. A SimpleDateFormat permits you to begin by selecting any user-defined patterns for the date-time formatting.

Time DateFormat Codes

If you need to specify a time format, then you can use the time pattern string. When using this template, all the ASCII letters are reserved as the pattern letters and it is termed as following:

Date Formatting Using the printf

Time and Date formatting is performed easily using a printf method. You can make use of the two-letter format and begin with the t and it ends in one of the letters of a table that are shown in the code below.

Java Notes for Beginners

It is not advisable to supply the date numerous times to format all the parts. So, you can use the format string that indicates an index of an argument that should be formatted. On doing that the index should automatically follow the % and it should be eliminated by a $.

Time and Date Conversion Characters

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Java Regular Expression

The Regular Expressions are a unique sequence of characters that helps you to find or match the set of strings, or other strings, upon using a specialized syntax that is held in the pattern. It can be used for editing, searching, or for manipulating the text or data. In this Java Tutorial for beginnerslet us see in detail the Regular Expressions that are used in Java.

Usually, the java. util. regex pack comprises of three classes and they are

• Pattern Class 
• PatternSyntax Exception 
• Matcher Class 

• Pattern Class - The Pattern Objects is an organized interpretation of regular expressions. A Pattern Class usually gives no Public Constructors. For creating the pattern, initially, you should call one of the public static compile() methods that send back the Pattern object. These methods usually accept a regular expression as a first argument.  
• PatternSyntax Exception - These are the objects that are the unchecked exception that notifies the syntax error on the regular on regular expression pattern. 
• Matcher Class - The Matcher Objects are the engine that represents the patterns and it executes the match operations counter to the input string. Likewise a Pattern Class, the Matcher illustrates the no public constructors. You can gain the Matcher Object by calling the matcher() method on the Pattern object. 

Capturing Groups

This is one of the ways of treating different characters as one unit. It is created by placing characters that should be organized inside the set of parentheses. For instance, a regular expression (Apple) creates one group that contains the letters "A", "P", "P", "L", and "E". Capturing the groups is counted by the opening parentheses from left to the right side.

In these expressions ( (A) (B(C))), for instance,

• ((A)(B(C))) 
• (A) 
• (B(C)) 
• (C) 

Identifying the groups that are available in these expressions are called a group count method on the matcher object. A group count method sends back the int that displays the total number of captures that the group presents in a matcher's pattern.

Also, there is a special group, group 0, that always interprets the complete expression. And this group will not be accommodated in the total report of the groupCount.

Syntax of Regular Expression

Different Methods of a Match Classer

The Index methods give us resourceful index values that showcase the exact match where it is found in an input string.

• public int start) - It helps in sending back the start index of a previous match.  
• public int end() - It refutes the offset only after when the last characters are matched. 
• public int start(int group) - This sends back the beginning of an index that is laterally captured to the given group at the preceding match operations.  
• public int end(int group) - It sends back the offset of the last character of concatenation and it is clocked by the set that is given at the older match operation. 

Study Methods

A Study method reviews an input string and it sends back the Boolean that points out whether the pattern is found or not. Some of the common study methods are listed below -

• public boolean find() - It helps in identifying the progression of an input sequence that adheres to the pattern.  
• public boolean lookingAt() - It tries to match the complete region against a pattern.  
• public boolean matches() - It tries to match the complete region against a pattern.  
• public boolean find (int start) - It helps in resetting the matcher and then it tries to identify the concatenation of input sequence that coheres to the pattern, that begins at the beginning of a specific index. 

PatternSyntax Exception Class Methods

This is an unchecked exception that denotes the syntax error on the regular expression pattern. A PatternSyntaxException class gives the below methods for identifying where it went wrong

• public int getIndex () - It restores the error index 
• public String getMessage () - This sends back the multi-line string that consists of a description of a syntax error along with its index. Also, it sends back the erroneous regular expression pattern and the visual indication of an error-inside within a pattern.  
• public String getDescription () - It helps in reclaiming the description of the error.  
• public String getPattern () - It restores the erroneous usual expression pattern. 

Java Methods

It is the compilation of statements that are organized together for performing the operations. You can call the System.out.println() method, for instance, the system can execute different statements for displaying the message on the console.

In this Java Fundamental Tutorial, you will comprehend how to create your methods with or without returning the values for invoking a method and to apply the method of abstraction to the program design.

For creating the Method

Consider the below example

Syntax

Over here,

• int - return type 
• public static - modifier 
• methodName - It is the name of a method 
• int a, int b - It is the list of parameters 
• a, b - It is the formal parameters 

A Method definition consists of a method body and method header.

Syntax

The above syntax also includes:

• returnType - This method shall return the value 
• modifier - It explains the access kind of method and this is optional for use. 

Parameter List

It is the list of parameters, that is the number, order, and type of parameters of the method. These are the optional methods that consist of zero parameters.  

method body

An method body describes what a method performs with the statements. 

nameOfMethod

It is the method name. A method signature includes the parameter list and the method name. 

Method Calling

Generally, to use a method, it must be called. There are two types through which a method can be called, to be precise, a method that returns the value and a method that doesn't return anything.

The steps of method calling are simple.

In case assuming that the program calls a method, then the program controls are also relocated in the called method. Then, a called method sends the control to a caller on two conditions and they are:

It sends back the statement that is executed. It reaches to a method that uses the ending closing brace.

A method that returns the void is termed as the call to statement.

For Example

This method sends back the value that shall be understood using the below example

int result = sum (6,9)

A Void Keyword

A Void Keyword permits us to create methods that do not return the value. Here, in the example given below, let us take into consideration the void method for the methodRankPoints. It is a void method that can't refute the value. To call, the void method, it should be a statement, i.e it must be methodRankPoints (255.7); This is the Java Statement that ends with the semicolon as shown below

Passing the Parameters by Value

When you work under a calling process, the arguments should be passed. It should be in the structure that is similar to the corresponding parameters in the method of the specification. A parameter shall be passed utilizing the reference or value. While passing the Parameters, the value indicates calling the method with the parameter. This is how the argument value is passed to the parameter.

Method Overloading

In case if a class has more than two methods with the same name, but with different parameters, this is known as method overloading. This is a contrast to an overriding method. When using the overriding method, you should have the same method type, name, and the number of parameters.

By using the Command-Line Arguments

At times, you may need to pass a few information to the program where you run them and it is accomplished by passing the command-line arguments to main().

The Command-Line argument is the piece of information that directly pursues a program's name on a command line when it is executed. Also, it is easy to access the command-line arguments from the Java Program. It stacks the Strings in a String array that is passed to the main ()

The Finalize () Method

It describes the method that shall be invoked just before the object's final elimination by using a garbage collector. A method is called for finalize () and this can be utilized for checking that the object is eliminated neatly.

For instance,

You may use the finalize() for making sure that the open file is gained by an object that is closed. In case if you want to add the finalizer to a class, you must describe the finalize() method. The Java runtime calls the method while it is about to recover the object of that class. Inside a finalize() method, you can mention the actions that should be executed before the object that is going to be eliminated.

Over here the keyword is shielded with the specifier that halts the access to the finalize() by code that is described outside the class.

It denotes that you can determine when or how they finalize would be executed. For instance, by any chance, if your program ends prior to the process of garbage collection, then at any cost the finalize () can not be executed.

Java I/O

The Java I/O package comprises almost all the classes you may require to execute the input and out in Java. And all these streams interpret the input source and the output destination. The Java stream in the Java.io package backs the data like an object, localized characters, and primitives.

Stream

The Stream is the sequence of the Data. In Java, you can stream the composed of bytes.

In Java, there are 3 streams that are developed automatically and all these streams are hooked with a console.

• System.in - Standard Input Stream 
• System.out - Standard Output Stream 
• System.err - Standard error stream 

The Code that is used for getting the Input from the Console is

int i=System.in.read();//returns ASCII code of 1st character

System.out.println((char)i);//will print the character

The Code for printing the error message and output to the consoles are

System.out.println("simple message");

System.err.println("error message");

The difference between the Input Stream and Output Stream

Input Stream

The Java Application basically uses the input stream for reading the data from the source, it can be anything like a socket, peripheral, an array, or a file.

Output Stream

The Java Application uses the Output Stream for writing the data for a specified destination, it can be anything like a socket, peripheral, an array, or a file.

The Diagram that is given below helps you to comprehend the Java Input and Output Stream easily

Input Stream Class

An InputStream Class is the abstract class and it is a superclass of all the classes that depicts the input stream of the bytes.

The Useful Approaches of the Input Stream

Output Stream Class

It is an abstract class. This is the Superclass of the gross classes that interprets the output of the stream of bytes. The output stream acquires output bytes and returns back a few to them for syncing.

The Useful Approaches of the Output Stream

Java Exceptions

Usually, the Exceptions are the problems that crop up during the time of an execution program. Suppose if an Exception takes place the normal flow of a program will be disrupted and that application terminates unnaturally, that is not advisable, hence these exceptions should be handled carefully.

The Exception can take place because of numerous reasons. Below is the situation where the exception takes place,

• In case if the user has entered into unauthorized data (data i.e invalid)  
• If a Network Connection has been lost in between the communication or if the JVM is out of memory.  
• A file that is needed to be opened but if you are unable to identify it.  

The Exceptions here are developed because of the program error, user error, or other physical resources that failed in some manner.

Based on this situation, in this Java Programming Tutorial, we have categorized the Exception into three and you should comprehend them to know how these exception handling work in Java,

• Checked Exceptions 
• Unchecked Exceptions 
• Errors 

Checked Exceptions

The Checked Exceptions is the exception that is verified by the compiler during the time of compilation and these are termed as the compile-time exceptions. One can not avoid these exceptions just like that, the programmer must take care of these exceptions.  

Unchecked Exceptions

The Unchecked Exceptions are the exceptions that take place at the time of execution. It is termed as the Runtime Exceptions. It includes the programming bug-like errors and other irregular uses of the API's The Runtime Exceptions are neglected during the compilation.  

Errors

These are not the kind of exceptions, but these are the problems that appear beyond the limit of a programmer or a user. The Errors are generally ignored in your code as you can hardly perform anything about the error. For instance, if the Stack Overflow takes place, the error would set in and also it shall be ignored during the time of compilation. 

Exception Hierarchy

Every Exception class is the Subtypes of java. lang. Exception class. An Exception class is the hierarchy of a throwable class. Apart from an exception class, there are additionally subclasses that are termed as Error and it is borrowed from a Throwable class.

The Errors are the abnormal conditions that take place at times of severe failures and these can not be managed by Java programs. The Errors are navigated to denote the errors that are generated by the runtime environment. For instance, An, JVM is usually out of Memory. Usually, the programs may not be able to recover from the errors. An Exception class consists of two main subclasses and they are the RuntimeException Class and IOException class.

Now let us see a brief description of the Exception Methods

• public Throwable getCause() - It helps in sending back the cause of exceptions that are depicted by the Throwable Object. 
• public void printStackTrace() - It helps in printing the result of the toString() with a stack trace of the error output stream or System.err. 
• public String toString() - It refutes the name of a class that is concatenated to the result of the getMessage(). 
• public String getMessage() - This refutes the detailed text of the exception that has taken place. It is the text which is booted on a Throwable constructor. 
• public Throwable fillInStackTrace() - It fills in the Stack of the Trace of this Throwable object with the present stack trace and it adds to the before the information on the stack trace.  
• public StackTraceElement [] getStackTrace() - It refutes the arrays that comprise the element from a stack trace. An element on the index 0 epitomizes the top of a call stack. The ending element in an array epitomizes the type of the bottom call stack.  

Catching Exception

This approach captures the Exception using the blend of catch and tries keywords. The Codes that are not beyond the try/catch block are termed as the protected code and the syntax for using a try/catch seems more or less similar.

A Code that is prone to an exception that is placed on the try block. Whenever the exception takes place, it is managed by the catch block that is related to it. All the Try blocks must be followed automatically using a catch or the final block.

The Catch Statement engages in asserting the kinds of exceptions that you are trying to capture. If the exception takes place on the protected code, then the catch block that supersedes a try is verified. If a type of exception has taken place in a catching book is listed, then the exceptions are passed for catching the block that is more like the argument than it is on to the passed method of a parameter.

Multiple Catch Blocks

The Try Block shall be superseded with different catch blocks.

Throw/ Throws keyword

If a method can not tackle the checked exception, then the method should term itself using the throw keyword. A throw keyword crop ups at the conclusion of the method signature.

Common Exceptions

In Java, you can describe two categories of errors and exceptions.

• JVM Exceptions - It is the Exceptions/ errors that are logically and exclusively thrown by a JVM. For instance: NullPointerException, Class Cast Exception, an ArrayIndexOutOfBoundsException. 
• Programmatic Exception - These are the exceptions that are thrown directly by an application or by the API Programmers. Example: IllegalStateException, IllegalArgumentException. 

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Java Inner Classes

In this Java Tutorial, like the Variables, Methods of the class can also have the other class as an owned member. Writing the class in something else is permitted in Java. A Class that is written in is known as a nested class. The Class that occupies an inner class is termed as an outer class.

Syntax

Below is the Syntax for the inner demo and outer demo in the nested class

The Nested Classes are further classified into two types and they are

• Static Nested Classes 
• Non-Static Nested Classes 

• Static Nested Classes - It is the Static Member of a Class 
• Non-Static Nested Classes - It is the Non-static Member of the Class 

Static Nested Classes

The Static Inner Class is the Nested class that a Static Member of the Outer Class. This shall be accessed past without calling the outer class and by using the other static members. Unlike the Static Members, the static nested may not need to have access to the instance methods and variables of an outer class.

Syntax

Inner Classes ( Non-Static Nested Classes)

The Inner Classes are the Security systems in Java. It is a known fact that the class shall not be combined with an access modifier in private, however, when you accept a class in the process of another class, later the inner class shall be made as private. It is also used for ingressing the private members of the class. It is of three kinds based on the kinds and they are

• Inner Class 
• Method-local Inner Class 
• Anonymous Inner Class 

Inner Class

Building an inner class is more simple. All you need is to write the class in a class. In contrast to a class, the inner class shall be private and when you declare the inner class is private, you can not access it from the object that is outside the class.

Accessing Private Members

As specified earlier, the inner classes are used for pervading the private members of the class. In case, the class consist of a private member for pervading them, then write the inner class inside it and then return them to the private members from the method in the inner class, for example, getValue() and certainly from the other class you can call a getValuw() method to the inner class.

Method-Local Inner Class

One of the prime features of Java is that you can write the Class in a method and it would mostly be of local kind. The Local variables and the scope of an inner class are curbed within a method.

The Method-Local inner class shall be called only with a method where an inner class is described.

Anonymous Inner Class

The Inner class that is stated without the class name is called Anonymous Inner Class. In the event of Anonymous Inner Class, it should be stated and called at the same time. Usually, it is used while you are required to nullify a method of the interface or class.

Java Inheritance

The Java Inheritance is the System on which the object obtains every behavior and properties of the parent object. This is the most important part of the OOPs.

The theory behind the inheritance in Java is you can build new classes that are built on the existing classes. If you derive from the existing class, then you can rephrase the fields and methods of a parent class. Further, you can also enumerate fields and methods in the current class as well.

Usually, the inheritance depicts the IS-A relationship that is comprehended as the parent-child relationship.

Reason to use the Inheritance in Java

• It is used for Method Overriding  
• Code Reusability 

Different Terms used in Inheritance

• Child Class/Sub Class - It is a class that derives from the other classes. This is also known as the derived class, child class, or the extended class. 
• Class - The Class is the set of objects that have general properties. It is the blueprint or template from where the objects are built.  
• Parent Class/ Super Class - It is the Class from where the subclass derives the features. This is also termed as the Parent Class or the Base class. 
• Reusability - The very name itself indicates the structure of reusability and it allows you to reuse the methods and fields of an existing class where you can build the new class. Also, you can use similar methods that are already described in the earlier class. 

The Extended keywords denote that you are building the new class that is inherited from the existing class. The term "extends" denotes an increase in functionality. The term Java is the class that is derived and it is called the superclass or parent, and this new class is termed as the subclass or child.

Java Overriding

In this Java Programming Tutorial let us see about the Overriding. In case if the class is derived from the method of its superclass, then you have the possibility to override a method that is given and that which is not marked as the final. The advantage of the overriding is the capacity to describe the behavior that is specific to a subclass type and it means the subclass shall deploy the parent class method on the basis of the needs. Based on the object-oriented terms, overriding here indicates overriding the performance of the existing method.

Rules should be followed for implementing the overriding method

• The Methods that are stated as final can not be overridden.  
• An Argument list must be completely similar to that of an overridden method.  
• An Instance method shall be overridden only when it is derived from the subclass. 
• A return kind must be similar or the subtype of a return type should be stated on the original overridden method on the superclass. 
• The Methods that are stated as the Static shall not be overridden however, it can be redeclared again. 
• When the method is unable to be derived then it shall not be overridden.  
• An access level shall not be restrictive and it can not be overridden for the method's access level. For instance: When the Superclass method is not stated publicly, then overriding the method on the subclass shall not be either protected or private.  
• The Subclass is a completely different package that can override only a non-final method and it is stated as protected or public. 
• The possibility of overriding a constructor is impossible. 

Java Polymorphism

Polymorphism means the capacity of the object to hold any form. The general use of polymorphism takes place in OOPs where the parent class reference is used for indicating the child class object.

All the Java objects shall pass above one IS-A test that is termed to be polymorphic. Almost, every object in Java is Polymorphic since the object shall pass the IS-A test on its own kind and for a class object.

The most important factor is that it is possible only to access the object via a reference variable. And the reference variable is of only one type. If it is stated once, then the kind of reference variable shall not be modified.

A reference variable shall be assigned again to the other objects that are given is not stated as the final. The kind of reference variable shall find the methods through which it can invoke the object.

The reference variable shall indicate any object of the stated type or the subtype of the stated type. The reference variable shall be stated as the interface or class type.

For Example

	public interface Vegetarian{}
	public class Animal{}
	public class Elephant extends Animal implements Vegetarian{}

Over here, the Elephant is termed to be polymorphic as it consists of different inheritance. The below is true for the above-given examples:

• A - Elephant IS - A Animal
• A - Elephant IS - A Vegetarian
• A - Elephant IS -A Elephant
• A - Elephant IS - A Object

If you apply the reference variable details to the Elephant Object reference, then the following declarations are considered to be legal

For Example

	Elephant e= new Elephant();
	Animal a = e;
	Vegetarian v = e;
	Object o = e;

All reference variables e, a, v, o, indicate the same Elephant object in the stack.

Java Abstraction

Abstract Class

The Class that is stated within the abstract keyword is called the Abstract class in Java. You have abstract and non-abstract methods. In this Java Tutorial, let us first get a clear understanding of what abstraction is all about.

Abstraction

It is the method of hiding the operation details and displaying only the functionality to a user.

It displays only the vital things to a user and shields the internal facts, like sending a message where you enter a text and send it. The users wouldn't be aware of the internal processing of a message delivery process. Abstraction permits you to concentrate on the performance of the object rather than the process that is involved in a performance.

Methods to reach Abstraction

There are two different methods for achieving abstraction in Java and they are

• Abstract Class (0 to 100%)
• Interface (100%)

The Abstract Class in Java

The Class that is stated as the abstract is called the abstract class. You can have abstract & non-abstract types. It should be extended and this method should be implemented. And it can't be called.

Java Notes for beginners

• The Abstract Class should be stated with the abstract keyword.
• It consists of Abstract & Non-abstract types.
• This shall not be called.
• An Abstract class could have static and constructor types as well.
• It has final methods that shall force a subclass for not changing the body of a method.

Rules of the Java Abstract Class

• The Abstract Class should be stated within the abstract keyword
• The Abstract Methods have final methods.
• The Abstract Class shall have the constructor and static methods
• The Abstract Class can have the Abstract and Non-Abstract types
• This can be called.

For Example of Abstract Class

	abstract class A {}

Abstract Practice in Java

The Method that is stated as abstract and that which does not have the operation is called the abstract method.

For Example

	abstract void printStatus();//no method body and abstract 

Example

Over here, the Cycle is the abstract class that consists of only one abstract process run. The Implementation is given by the Lady Bird Class.

	abstract class Cycle{  
	abstract void run();  
	}  
	class Lady Bird 4 extends Bike{  
	void run(){System.out.println("running safely");}  
	public static void main(String args[]){  
	Cycle obj =  Lady Bird4();  
	obj.run();  
	}  
	}  

Java Encapsulation

Encapsulation is one of the basics of the four OOP concepts. The rest are abstraction, polymorphism, and inheritance.

The Encapsulation in Java is the structure of wrapping data and code that are performing on the data together as a single unit. Over here the variables of the class are shielded from the other classes and it is possible to pervade via the methods of its present class. Hence, this is called Data hiding.

For achieving the Encapsulation in Java

• It should state the variables of the class as the private.
• It gives the Public Getter and Setter methods for viewing and modifying the values of variables.

Advantages of Encapsulation

• It Declares the variables of the class as the private
• It enables public getter and setter manners to view and modify the values of the variables.

Java Interfaces

The Interface is the reference kind in Java. It is identical to the class and the compilation of the abstract methods. The class shall instrument interface, and derive the abstract methods to an interface. Further with the Abstract methods, the interface consists of the static method, nested type, constants, and default methods. The Method bodies only prevail for the default and static methods.

Writing the interface that is identical to Class. The class defines the behavior and characters of an object. The interface comprises the attributes of the class instruments.

Except for the Class which instruments an interface is abstract, of all methods of an interface that has to be described in a class.

The Interface is similar to that of a class in the below methods:

• An Interface is usually written in the file that is within the .java extension of a similar interface that adheres to the name of a file.
• The Interface shall consist of more number of methods.
• Usually, the byte code of the interface surfaces in the .class file.
• Interfaces that surface in the packages and to its interrelated bytecode file should be found in the directory structure that adheres to the package name.

Yet the interface is so different from the class in multiple ways and it includes

• It is not possible to call the interface
• All the methods in the interface are abstract.
• An Interface will not comprise any instance fields. A field that appears on the interface must be stated both in Final and Static.
• The interface does not consist of any constructors.
• The interface shall expand the different interfaces.
• An interface is not only expanded by class, but it is instrumented by the class.
• The Interface can extend different interfaces.

Declaring an Interface

The interface keyword is used for declaring the interface

Implementing Interfaces

When the class instruments the interface, you can use the class as the signing contract and adhering to perform a particular behavior of an interface. In case, when the class fails to execute all functions of an interface, then the class should mention itself as abstract. The Class utilizes the implement keyword for instrumenting the interface. An implement keyword surfaces in a class declaration and it expands the portion of a declaration.

In case the overriding methods are described in the interface, then numerous rules have to be followed

• An implementation Class itself must be abstract and so the interface type may not be required to implement.
• A signature of an interface method and similar return type or a subtype must be maintained while overriding methods.
• A checked exception may not be declared on the implementation methods apart from the ones which are declared by a subclass or interface method of the ones that are stated by an interface method.

In case if the implementation interfaces, then there are numerous rules

• A class can instrument above one interface at a time.
• A class shall extend can broaden only one class and it implements more than one interface.
• The Interfaces shall extend the other interface in the same way as that of the class would extend the other class.

Extending Interfaces

The Interface shall extend other interfaces that are similar to the way that the class shall extend to the other class. An extended keyword is utilized for expanding the interface and a child interface that derives the method of a parent interface.

Extending Different Interfaces

The Java Class shall broaden only one of the parent classes. The different inheritances are not permitted. The Interfaces are no class, and the interface shall extend above one parent interface.

An Extend keyword is utilized only once and a parent interface is stated in the comma-separated list.

Tagging Interfaces

The general use of an extending interface takes place when a parent interface does not consist of any methods.

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Packages

The Packages are utilized in Java to avoid the conflicts in access and control for making the location/ searching and the use of the classes, annotation, enumerations, and interfaces.

The Package shall also be defined as the set of related types like (enumerations, classes, interfaces, and annotations ) that give access to the namespace and protection management.

Other existing packages that are comprised in Java are

• java.io - The Classes for the Output and Input functions are wrapped in the packages
• java-lang - These packages are the fundamental classes

The Programmers are defined on the package of bundle groups such as interfaces/ classes, etc.

This is a good method of practice that is associated with classes that deploy a programmer and you can identify the interfaces, annotation, enumerations, and classes.

As the package develops the new namespace there will not be any conflicts in names and also the names that are in other packages. Utilizing these packages is simpler to provide entry control and it is easy to find the other associated classes.

Creating Packages

When you create a package, you must select the name of a package and consists of the package statement with a name on the top of all the source file that consists of the enumerations, interfaces, classes, and annotation types you are planning to add into a package.

A package statement should be the starting line of the source file. There can also be only a single package statement on every source file and this is applicable for all kinds of files.

Supposedly if the package statement is not utilized then the interfaces, annotation, class, and enumeration types would not be placed on a present default package.

For compiling the Java programs along with the package statements you can use the -d option as given below

	javac -d Destination_folder file_name.java

Then the folder with the provided package the name is developed on the definite destination and this is gathered on the class files that and would be placed on the folder.

The Import keyword

If the class is required you must utilize the other class on a similar package, the package may not be used. The Classes on a similar package can identify the other without any exclusive syntax.

Structure of the Directory Package

The two important results that take place in the class of the package

• The name of a package that turns out to be part of the name of a class and should be mentioned in the earlier section.
• The name of a package should adhere to the directory structure and it should cohere with the bytecodes that reside along with it.

Below is the simple way to handle your files in the Java

Place the Source code to an interface, enumeration, or the annotation kind on the text file that the name is simpler than the name of a kind and on the extension is.java.

For Instance,

	// File Name : Apple.java
	package fruit;

	public class Apple {
	// Class implementation.   
	}

Output

	....\fruit\Apple.java

The qualified class and the pathname shall be as follow:

• Class name -> fruit. Apple
• Pathname -> fruit\Apple.Java ( in the windows system)

Usually, a company uses the reverse Internet domain name for the package names.

For Example

If a company has the Internet domain name - windows.com, then all the package names shall begin with the com. windows. All the components of a package name must adhere to the subdirectory.

Advanced Java Tutorial

Data Structures

The Data Structures that are given by the Java utility package are robust and can execute a range of functions. The Data structures comprise of the below classes and interface,

• Vector
• Stack
• Enumeration
• BitSet
• Hashtable
• Properties
• Dictionary

Vector

A Vector class has more resemblance to the traditional Java array, apart from that it can also manipulate as needed, and it can consist of new elements. Just like an array, the elements of the vector object are controlled through the index in a vector. The best part of using a vector class is you need not care about setting it to the particular size on creation, it can adjust (shrink/enlarge) itself when it is required.

Stack

A Stack Class deploys the LIFO method i.e Last-in-first-out, a stack of elements. Over here the Stack is the vertical stack object, where you can pass the new elements and get them stacked on the above of others. In case if you pull the element off a stack, then this moves to the top. To make it easier, the closing element that you add to a stack is the one that appears like the back off.

Enumeration

It is not a data structure by itself, but enumeration is more important within the conditions of the other data structures. An Enumeration is an interface that describes the means for recovering the successive elements from the data structure.

For Example, Enumeration describes the method that is termed as the nextElement and it is used for obtaining the immediate (next) element in the data structure queue that consists of different elements.

BitSet

A Bitset Class deploys the set of flags or the bits that could be fixed and cleared individually. It is more useful in case you need to keep up to the set of Boolean values. You can easily designate the bit all the value and it can be fixed or cleared as appropriate.

Hashtable

A Hashtable Class gives the space for organizing the data on the basis of the user-defined key structure.

For instance, on your address list hash table, you can sort, save the data based on the key like ZIP code instead of the particular person's name. The exact meaning of the keys in respect of the hash table is completely on the application of a hash table and the data it consists of.

Properties

The Properties are the subclass of the Hashtable. It is used for handling the list of values on which a key is a string and the string is also the value. Apart from this, the properties class is used by other Java Classes.

Dictionary

A Dictionary class is the abstract class that describes the data structures to map the keys to the corresponding values. It is more useful in a situation where you are unable to get access to the data through a specific key instead of the integer index. As the Dictionary Class is abstract, it gives a framework that is key-mapped data structure instead of the particular implementation.

Java Collections

A Collection in Java is the framework that gives the architecture for the store and it modifies the objects in the groups. The Java Collection shall accomplish all the operations that you must perform on the data like insertion, sorting, searching, deletion, and manipulation.

The Collection of the framework was curated to match the different goals like

A Framework permits numerous types of collection for working in an identical manner and it has a high degree of interoperability.

A Framework has to perform extremely well. The Implementation of the basic collections like ( linked lists, trees, dynamic arrays, and hashtables) must be highly efficient.

A Framework was created to extend or adapt to the collection in an easier manner.

Finally, the complete collection of a framework is curated on a set of common interfaces. There are numerous standard implementations like TreeSet, LinkedList, and HashSet, and these interfaces are given so that you can use them as they are and also deploy them on your collection when you choose.

The Collection of Framework is the unified architecture that is used for manipulating and interpreting the collections. All the Collections of the framework comprises of the following,

• Algorithms - It is the common method that is used for performing computations like sorting or searching an object that shall instrument the collection interfaces.
• Interface - It is the abstract data type that interprets the collections. The Interfaces permit the collections to modify freely irrespective of the facts of the representation. It is a common thing that in the Object-oriented language, an interface would build the hierarchy.
• Implementations - It is the detailed implementation of the collected interface and it is the renewable data structures.

Further, a framework describes different map classes and interfaces. Although the maps are not collections that are in appropriate use of a term, however, it is completely combined with collections.

The Collection Interface

In this Java Programming Tutorial let us see the collections framework that describes numerous interfaces.

• Map - It aids in mapping the distinct keys to the values.
• Collection Interface - It allows you to work with a set of objects and it is on the top list of the collection hierarchy.
• Set - It extends the Collection for handling sets that contain a distinct element.
• SortedSet - It helps in extending the Set for managing the sorted sets.
• Enumeration - It is the legacy interface that describes the method through which you shall enumerate elements from the collection of objects. The bequest interface is antiquated through Iterator.
• Sorted Map - It helps in enlarging the Map for managing the keys in ascending order.

The Collection Classes

Java supports you with you a set of benchmark collection classes that instrument the Collection interfaces. The Classes gives complete implementation that is used as it is and another abstract class, that gives the skeletal implementations which are used as the beginning points to create the definite collections.

Some of the Standard Collections are mentioned below

• Abstract List - It aids in extending the AbstractCollection and it deploys more List Interfaces.
• Abstract Collection - It deploys a more Collection interface.
• Abstract Sequential list - This Extends the AbstractList for the use by the collection that applies sequence instead of the random access of elements.
• Array List - It instruments the influential array on broadening the AbstractList.
• Linked List - It instruments the linked list on expanding the AbstractSequentialList.
• HashSet - It Extends the AbstractSet to make use of the hash table.
• TreeSet - This deploys the Set that is stored in the tree. It extends the AbstractSet.
• Linked HashSet - It lengthens the HashSet and permits the insertion-order iterations.
• Abstract Map - It deploys maximum Map Interface.
• Tree Map - It Expands the Abstract Map for utilizing the tree.
• Hash Map - This broadens the AbstractMap to utilize the Hash table.
• Weak Map - It expands the AbstractMap for utilizing the hash table that is in the limit of weak keys.
• IdentityHashMap - This broadens the AbstractMap and it makes use of the reference equality while compared to the documents.
• LinkedHashMap - This Expands the Hashmap for permitting the insertion-order iterations.

Below are the classes that give the skeletal implementation of the core collection interface for reducing the effort that is needed to deploy them,

• AbstractSet
• AbstractMap
• AbstractCollection
• AbstractList
• AbstractSequentialList

Collection Algorithm

A Collection Framework explains various algorithms that are practiced on the maps and collections. It is characterized as Static methods in the limits of the collection class.

The various methods that shall throw the ClassCast Exception that takes place when the experiment is made for analyzing the incompatible types or the UnsupportedOperationException, that takes place while the attempt is made for changing the unmodifiable collections.

Iterator

Usually, you may need to wheel to the elements in the collections. For instance, you may be required to demonstrate all elements. The simplest way for performing this is that you can deploy the iterator, which is actually the object that instruments either the Listiterator interface or the Iterator

An Iterator permits you to go through the collection or remove elements. The ListIterator shall broaden the Iterator for allowing modification of the elements and the traversal of the list.

Comparator

Both the TreeMap and the TreeSet stack the elements in a sorted manner. The Comparator demonstrates accurately everything about sorted order. It basically helps you to sort for the provided collection by any number or through multiple ways. Furthermore, this interface shall be applied for sorting any instance of whatever class.

Java Networking

It is the notion of bridging two or above computing devices in sync so that you can share the resources. The Java Socket Programming gives the competency to share data between various computing devices. The two major benefits of Java Networking are,

• You share the resources easily.
• You have the Centralized Software Management kit.

Java Networking Technology

In this Java Tutorial let us see the broadly-used Java Networking Terminologies

• Port Number
• MAC Address
• Protocol
• IP Address
• Socket
• Connection-oriented protocol

Port Number

The Port number is utilized distinctly for determining various applications. It operates as the endpoints of communication between applications. A port number is related to the IP address to communicate between two applications.

MAC Address

The MAC address ( Media Access Control) is the distinct identifier of the Network Interface Controller. The Network Node shall have a different NIC however everything with the distinct MAC.

Protocol

The Protocol is the compilation of rules that are generally used in communication. For instance - FTP, Telnet, TCP, SMTP, and POP.

IP Address

The IP Address is the distinct number that is designated to the node of the network. For example - 192.168.0.1 and this is compiled of the octets that length between 0 to 255. This is the logical address that could not be changed.

Socket

The Socket is the endpoint between the two ways of communication.

Connection-oriented protocol

On the Connection-oriented protocol, the affirmation is sent by a receiver. Even though it is slow, this is reliable. For Example - TCP.

Connectionless protocol

In the Connectionless protocol, the acknowledgment will not be sent by a receiver and it is not reliable but this is faster. For Example - UDP.

Java Socket Programming

The Java Socket Programming is utilized for communication between the applications which run on different JRE.

The Java Socket Programming can either be one that is connectionless or connection-oriented. The ServerSocket Classes and Socket is used for connecting the oriented socket programming. For connection-less socket programming, you can use the DatagramPacket and DatagramSocket.

A Client in Socket Programming should know two pieces of information and they are

• Port Number
• IP Address of the Server

Over here, we have demonstrated the example for one-way server and client communication. And here the Client dispatches the message to a server, and the server reads the text and later prints it. Exactly, here two classes are utilized and they are ServerSocket and Socket. A Socket Class is used for communicating to the Server and Client. With this, you can write and read the message. A ServerSocket Class is utilized at the server-side. An Accept() method of a ServerSocket Class halts the console till the client is connected. Later on the successful connection to the client, it sends the instance of the Socket to the server-side.

Socket Class

The Socket is the endpoint of communications among machines. A Socket Class is used for building the socket.

Some of the important methods

Server Socket Class

A ServerSocket Class is utilized for building the server socket. It is the object that is used in building the communication along with the clients.

Some of the important Methods are

Java URL

The abbreviation of the URL is Uniform Resource Locator. This directs to the resource that is on the World Wide Web. For instance,

An URL Consists of numerous information and they are

• Port Number - It is the optional character. If you write https://www.fita.com.70/trainingcenter/ the number 70 is the port number. In case there is no port number that is mentioned on the URL then it returns to -1.
• Directory Name or File Name - Here the index. jsp is the name of the file
• Protocol - The HTTP is protocol.
• IP Address or Server name - www.fita.in is the name of the server.

Predominantly used Java URL Class

Java InetAddress Class

The Java InetAddress Class demonstrates the IP address. A java.net.InetAddress also gives the methods for getting the IP of any hostname. An IP address is illustrated by the 32-bit or by the 128-bit which is the unsigned number. The instance of the InetAddress depicts the IP address that correlates with the hostname. There are two kinds of address types and they are Unicast and Multicast. A Unicast is the qualifier of the single interface where a Multicast is the qualifier of the set of interfaces. Further, the InetAddress consists of the cache mechanism that aids in storing the successive and non-successive host-name resolutions.

Important Methods of the InetAddress Class

Java - Sending Email

For sending the e-mail you should use the Java Application that is close enough, to begin with, where you must have installed the Java Activation Framework or the Javamail API to your machines. For downloading the recent version you can use Java's standard Website.

On downloading it successfully, you can unzip those files in a newly developed top-level directory where you can find out the total number of the jar files for both applications. All you have to do is that you must add the activation.jar and mail.jar to your CLASSPATH.

Java Multithreading

Java is considered to be one of the multi-threaded programming languages that means you can build a multi-threaded program using Java. The Multi-threaded program consists of two or more parts that shall run simultaneously and all the parts shall manage the various tasks simultaneously by making optimal use of the resources that are provided and when the computer has numerous CPUs.

The word multitasking means where there are numerous processes that share common operations of all resources like CPU. The Multi-threading widens the concept of multitasking into applications where you shall partition few applications in the limit of the single application and into individual threads. All the threads are capable of running collar OS aids in partitioning the operating period in the applications as well as to all the threads that are within an application.

Generally, the multi-threading allows you to write in a manner where different activities shall proceed with the same program altogether.

The Wheel of the Thread

Usually, a thread undergoes different stages. The flow-chart that is given below precisely explains the lifecycle of the thread.

Below are the detailed description of the Thread Lifecycle

• New - The New Thread take starts its life cycle with the new states. It prevails in this state up to when a program takes off with the thread and it is called a born thread.
• Runnable - Once the newly born thread begins its function, then the thread shall become runnable. The thread in this state is termed to be runnable as it is executing the tasks.
• Waiting - At times, the thread flux back to the runnable state when the other thread signals to the waiting thread to pursue the execution function.
• Time Waiting - The Runnable threads shall barge into the restrained waiting state for a definite period. The thread which is in this state shall flux back to a runnable state in case the allotted time interval is expired or while an event is awaiting its occurrence.
• Terminated - The Runnable thread moves into the terminated state where it tries to replete the tasks, if not then it would terminate itself.

Thread Priorities

All the threads in Java have a unique priority that supports operating the systems to identify the sequence through which the threads are being scheduled. The Java thread priorities are within the range of MIN_PRIORITY and MAX_PRIORITY. Where the MIN_PRIORITY is the constant of 1, and the MAX_ PRIORITY is the constant of 10. By default, all the threads are provided priority i.e NORM_PRIORITY which are constant of 5. The threads that are with higher priority are more important to the program and this should be designated to the processor time before the lower-priority threads. Yet, these threads' priorities shall not be guaranteed in the sequence on which the threads are executed; it depends more on the platforms.

Now in this Java Developer Tutorial, let us see how to build a thread on

In case, when your class is aimed for execution then the thread shall attain this implementation by the Runnable interface. Below are the fundamental steps in creating the thread,

Step-1

The first step you must do is that you should implement the run() method by enabling the Running interface. The method that gives the entry point to a thread and you shall upload the entire business logic to this method.

Syntax for run() method

	public void run( )

Step-2

The second type will instantiate the Thread object by using the below constructor-

Thread(Runnable threadObj, String threadName);

The thread by is the instance of the class that deploys the thread name and the Runnable interface is the name that is provided to a new thread.

Step-3

If the Thread Object is developed then you can begin it by calling the start() method, which shall execute the call to the run() method.

Syntax for the start() method

	void start();

Build the Thread by the Extending Thread Class

Java Applet Basics

The Applet is the Java Program and it runs on the Web browser. The Applet is the complete Java functional application as it consists of the entire Java API at its scraping.

Below are the major difference between the applet and the standalone Java application

• The Applet is the Java Class that boosts java. applet.Applet class.
• The Applets are devised to embed with the HTML Page.
• The main () method does not request the applet and the applet class may not define main ().
• If the user views the HTML page it consists of the applet and the code of the applet is installed into the respective user's machine.
• The JVM is needed for viewing the applet. The JVM shall either be a separate runtime environment or a plug-in to the Web browser.
• The Applets have stringent rules that shall be reinforced by a Web Browser.
• The Security of the applets is often attributed to the sandbox security when compared to the applet of the child playing on the sandbox with different rules which should be implemented.
• The JVM of the User's Machines develops the instance of an applet class and this requests different methods at the time of the applet's cycle.
• The Other Classes which the applet requires are downloaded into the single (JAR) Java Archive file.

The Applet Cycle

The Four methods in Applet Class provides you a framework in which you can build the serious applet:

• Start - It is the method that immediately calls the browser calls to init method.
• Init - It is the type that is aimed for initialization that is required for the applet. This is called later the param tags that are inside an applet tag that you have processed.
• Stop - It is the type that is immediately called when a user moves away from the page in which an applet sits. This can be called frequently on the same applet.
• Paint - It is requested automatically later by the start() method, and at any time the applet requires to refurbish itself in a browser. A paint() method is generally obtained from java.awt.
• Destroy - It is the method that is called if the browser closes down usually. When the applets are meant to be on the HTML page, then you can not usually leave the resources breach after the user leaves a page that consists of the applet.

The Applet Class

All Applet is the extension of java. Applet class. The base Applet class gives methods that are obtained from the Applet Class and it shall be called for obtaining the services and information from a browser context.

It consists of the following methods:

• Fetching the image
• Fetching the audio clip
• Plays the audio clip
• Resizing of the applet
• Getting the applet parameters
• Getting a Network location of an HTML file that consists of the applet
• Getting the Network location of an applet class directory
• It prints out the status text in the browser

Further, the Applet Class shall give the interface on which a viewer or the browser gains the information of the applet and the control operation of the applet's execution.

• Initializes an applet
• Destroys the applet
• Request the information regarding the version, copyright, and author of an applet
• It requests the description of a parameter and the applet identifies it
• Ceases the execution of an applet
• Begins the execution of an applet

An Applet Class that gives the default application of all the methods. Those applications shall be overridden when required.

Java Documentation

The Javadoc is the tool that comes with a JDK and this is used for developing Java Code documentation in the HTML format from the Java Source code and it needs the documentation of the predefined format.

The Java supports the following three types of comments.

• //'text - A compiler avoids everything from// till the end of a line.
• /*text*/ - A compiler avoids everything from the /* to*/

Java Useful Resources

Java Interview Questions

The Java Interview Questions and Answers are curated with a special focus to aid both the students and the working professionals who are preparing themselves for different Certification Exams and Job Interviews. This session is a complete compilation of the Important Java Interview Questions and Answers that are asked to fresher and experienced candidates in the interview.

Enlist the different access specifiers in Java?

• Public
• Private
• Default
• Protected

List the Advantages of Package in Java?

• The Packages evades the name clashes.
• It is easier to locate the related classes.
• The Packages give easier access control.
• You can also have the hidden classes which are not found outside the used package.

Name the types of constructors that are used in Java?

Java has two types of Constructors and they are,

Default Constructor?

Parameterized Constructor

Is it possible to make a Constructor final?

It is impossible to make the Constructor final.

Are the Constructors inherited?

No, the Constructors are not inherited.

For more: Click the link given below

Java - Quick Guide

• The Java Tutorial - It is the practical set of guides to the programmers who need to use the Java Programming language for creating the applications.
• Free Java Download - Download Java to your desktop from the Computer now.
• SunDeveloper Network- This is the official website that is used for listing down the API documentation, books, latest Java technologies, and other resources.
• JavaTM 2 SDK - This is the Official Site for the JavaTM 2 SDK, the Standard Edition.
• Java Tutorial - It is the practical guide for the programmers who need to use the Java Programming language for creating the applications.