Why Multiple Inheritance in Java not supported?

April 22, 2019 By javatution Leave a Comment

Multiple Inheritance in Java is not supported

For making Java language simple and avoid complexities present in earlier languages like c++, the founder of java(James Gosling) decided that java shouldn’t support Multiple Inheritance.

In a white paper titled “Java: an Overview” by James Gosling in February 1995(link) gives an idea on why multiple inheritance is not supported in Java.

Gosling on omission of Multiple Inheritance in Java

“JAVA omits many rarely used, poorly understood, confusing features of C++ that in our experience bring more grief than beneﬁt. This primarily consists of operator overloading (although it does have method overloading), multiple inheritance, and extensive automatic coercions.”

Ambugity problem due to Multiple Inheritance

If we try to do multiple inheritance in java we will come across an ambiguity problem. We will discuss about it below using an example.

Multiple Inheritance in Java is Not Supported

We have a super class A having a function called fun().
Two subclasses B and C extend class A providing their own implementation of fun() function.

Assume class D inherits from class B and class C.
If we create an object of class D and try to access function fun() guess what will happen.
i.e D obj=new D(); obj.fun();

This will lead to ambiguity problem. Because it’s difficult for java to decide which version of fun() function to execute, fun() of class B or fun() of class C. The above problem is also referred as diamond problem.

In c++ we have multiple inheritance and the problem is resolved using scope resolution operator. But java founders wanted to keep java simple and avoid complexities. Concepts like pointers, operator overloading are also avoided in java language for the same reason.

Multiple Inheritance in Java is not much required

Extending from two different classes having different implementations of a function is not much required in real world.

Filed Under: Java

Rock Paper Scissors Game using Java Programming

October 24, 2017 By javatution Leave a Comment

Developing Rock Paper Scissors Game using Java

In this example we are going to develop a Rock Paper Scissors Game using Java. Developing games while learning java enhances our programming skills.

The Rule of the Game are as follows:

Rock beats Scissors.
Scissors beats Paper.
Paper beats Rock.
Who ever wins 5 times first is the Winner.
In this example the game will be between a user and the computer.

Learn Core Java Properly through my Private Core Java Online Training to be able to write games in java easily.

Steps of the Rock Paper Scissors Java Program

We will create a class Player.java that represents the user who is going to play the game with the computer.
The class Computer.java represents the Computer that is playing with the user.
Driver.java is a helper class containing the Rock Paper Scissor constant variables and the business logic code.
RPS.java is the class containing the main function where the program execution will begin.
We will ask the user to enter his name. Then select one among ROCK PAPER SCISSORS.
Then we will let the computer randomly select ROCK PAPER SCISSORS.
We will use the business logic function to find out who wins. And every time we will display the selections made and who won.
The can decide to end the game any time.
We will keep a track of who wind 5 times first. And then display the winner.

Player.java will represent the User playing with the computer.

import java.util.Scanner;

public class Player {
	private String name;// Represents the Players name
	Scanner sc = new Scanner(System.in);
	// sc will help to take inputs from keyboard

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public void askName() {// Will let the user enter his name
		System.out.println("Please enter your name");
		name = sc.next();
	}

	public int getInput() {
		// This function lets the user do the selection among
		// ROCK PAPER SCISSORS
		// and return what has been selected
		System.out.println("Select  ROCK  PAPER SCISSOR");

		String input = sc.next();
		input = input.toUpperCase();
		char c = input.charAt(0);
		// checking the 1st character in the input
		if (c == 'R')
			return Driver.ROCK;
		else if (c == 'P')
			return Driver.PAPER;
		else if (c == 'S')
			return Driver.SCISSORS;
		else {
			getInput();
			return 0;
		}
	}

	public boolean playAgain() {
		// This function will ask if the user wants to
		// play again and return true or false accordingly.
		sc = new Scanner(System.in);
		System.out.print("Do you want to play again? ");
		String userInput = sc.nextLine();
		userInput = userInput.toUpperCase();
		return userInput.charAt(0) == 'Y';
	}
}

import java.util.Scanner;

public class Player {

private String name;// Represents the Players name

Scanner sc = new Scanner(System.in);

// sc will help to take inputs from keyboard

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public void askName() {// Will let the user enter his name

System.out.println("Please enter your name");

name = sc.next();

}

public int getInput() {

// This function lets the user do the selection among

// ROCK PAPER SCISSORS

// and return what has been selected

System.out.println("Select ROCK PAPER SCISSOR");

String input = sc.next();

input = input.toUpperCase();

char c = input.charAt(0);

// checking the 1st character in the input

if (c == 'R')

return Driver.ROCK;

else if (c == 'P')

return Driver.PAPER;

else if (c == 'S')

return Driver.SCISSORS;

else {

getInput();

return 0;

}

public boolean playAgain() {

// This function will ask if the user wants to

// play again and return true or false accordingly.

sc = new Scanner(System.in);

System.out.print("Do you want to play again? ");

String userInput = sc.nextLine();

userInput = userInput.toUpperCase();

return userInput.charAt(0) == 'Y';

}

Computer.java will represent the computer that is playing with the user.

import java.util.Random;


public class Computer {
	// This function helps the computer do the selection among ROCK,
	// PAPER,SCISSORS
	// we have used Random class from java.util.
	public int getInput() {
		Random random = new Random();
		int input = random.nextInt(3) + 1;
		return input;
	}
}

import java.util.Random;

public class Computer {

// This function helps the computer do the selection among ROCK,

// PAPER,SCISSORS

// we have used Random class from java.util.

public int getInput() {

Random random = new Random();

int input = random.nextInt(3) + 1;

return input;

}

Driver.java is a helper class containing constants and business logic.

public class Driver {
	//These instance variables will act as constants through out the project
	public static final int ROCK = 1;
	public static final int PAPER = 2;
	public static final int SCISSORS = 3;

	//This function will help to display who selected what
	public static void display(String who, int s) {
		switch (s) {
		case Driver.ROCK:
			System.out.print(who + " selected ROCK   ");
			break;
		case Driver.PAPER:
			System.out.print(who + " selected PAPER   ");
			break;
		case Driver.SCISSORS:
			System.out.print(who + " selected SCISSORS   ");
			break;
		default:
			break;
		}
	}
	//This function contains the actual buisness logic
	//and help to decide who won
	public static int compareSelections(int userSelection, int computerSelection) {
		if(userSelection==computerSelection) return 0;
		switch (userSelection) {
		case ROCK:
			return (computerSelection == SCISSORS ? 1 : -1);

		case PAPER:
			return (computerSelection == ROCK ? 1 : -1);

		case SCISSORS:
			return (computerSelection == PAPER ? 1 : -1);
		}
		return 0;
	}
}

public class Driver {

//These instance variables will act as constants through out the project

public static final int ROCK = 1;

public static final int PAPER = 2;

public static final int SCISSORS = 3;

//This function will help to display who selected what

public static void display(String who, int s) {

switch (s) {

case Driver.ROCK:

System.out.print(who + " selected ROCK ");

break;

case Driver.PAPER:

System.out.print(who + " selected PAPER ");

break;

case Driver.SCISSORS:

System.out.print(who + " selected SCISSORS ");

break;

default:

break;

}

//This function contains the actual buisness logic

//and help to decide who won

public static int compareSelections(int userSelection, int computerSelection) {

if(userSelection==computerSelection) return 0;

switch (userSelection) {

case ROCK:

return (computerSelection == SCISSORS ? 1 : -1);

case PAPER:

return (computerSelection == ROCK ? 1 : -1);

case SCISSORS:

return (computerSelection == PAPER ? 1 : -1);

}

return 0;

}

RPS.java contains the main method. This is the starting point of program execution.

public class RPS {
	//Instance variables declaration
	private Player player;
	private Computer computer;
	private int playerScore;
	private int computerScore;
	private int numberOfGames;

	//Default Constructor initializing the instance variables
	public RPS() {
		player = new Player();
		computer = new Computer();
		playerScore = 0;
		computerScore = 0;
		numberOfGames = 0;
	}
	public static void main(String[] args) {

		RPS rps = new RPS();//Initialization occured.
		rps.getplayerName();//Getting user name
		rps.startGame();
	}
	//This function is called recursively till the player wants to play.
	//It is even exited if the user of computer completes the first 5 wins.
	public void startGame() {
		int playerinput = player.getInput();
		Driver.display(player.getName(), playerinput);
		// Get moves
		int computerinput = computer.getInput();
		Driver.display("computer", computerinput);
		// Compare moves and determine winner
		int compareResult=Driver.compareSelections(playerinput, computerinput);
		switch (compareResult) {
		case 0: // Tie
			System.out.println("Tie!");
			break;
		case 1: // player wins
			System.out.println(player.getName()+ " Beats " + "computer" +" You won!");
			playerScore++;
			break;
		case -1: // Computer wins
			System.out.println("Computer" +" Beats "+ player.getName()+" You Lost!");
			computerScore++;
			break;
		}
		numberOfGames++;
		if(playerScore==5)
		{
			System.out.println(player.getName()+" HAS WON THE GAME.............");
			new RPS();
		}
		if(computerScore==5)
		{
			System.out.println("Computer "+" HAS WON THE GAME............");
			new RPS();
		}
		// Ask the player to play again
		if (player.playAgain()) {
			System.out.println();
			startGame();
		} else {
			printStats();
		}
	}
	//helps to get the users name
	public void getplayerName() {
		player.askName();
	}
	//Prints the result.
	public void printStats()
	{
		System.out.println("Number of games played is "+numberOfGames);
		System.out.println(player.getName()+"'s score "+playerScore);
		System.out.println("Computers score "+computerScore);
	}
}

public class RPS {

//Instance variables declaration

private Player player;

private Computer computer;

private int playerScore;

private int computerScore;

private int numberOfGames;

//Default Constructor initializing the instance variables

public RPS() {

player = new Player();

computer = new Computer();

playerScore = 0;

computerScore = 0;

numberOfGames = 0;

}

public static void main(String[] args) {

RPS rps = new RPS();//Initialization occured.

rps.getplayerName();//Getting user name

rps.startGame();

}

//This function is called recursively till the player wants to play.

//It is even exited if the user of computer completes the first 5 wins.

public void startGame() {

int playerinput = player.getInput();

Driver.display(player.getName(), playerinput);

// Get moves

int computerinput = computer.getInput();

Driver.display("computer", computerinput);

// Compare moves and determine winner

int compareResult=Driver.compareSelections(playerinput, computerinput);

switch (compareResult) {

case 0: // Tie

System.out.println("Tie!");

break;

case 1: // player wins

System.out.println(player.getName()+ " Beats " + "computer" +" You won!");

playerScore++;

break;

case -1: // Computer wins

System.out.println("Computer" +" Beats "+ player.getName()+" You Lost!");

computerScore++;

break;

}

numberOfGames++;

if(playerScore==5)

{

System.out.println(player.getName()+" HAS WON THE GAME.............");

new RPS();

}

if(computerScore==5)

{

System.out.println("Computer "+" HAS WON THE GAME............");

new RPS();

}

// Ask the player to play again

if (player.playAgain()) {

System.out.println();

startGame();

} else {

printStats();

}

//helps to get the users name

public void getplayerName() {

player.askName();

}

//Prints the result.

public void printStats()

{

System.out.println("Number of games played is "+numberOfGames);

System.out.println(player.getName()+"'s score "+playerScore);

System.out.println("Computers score "+computerScore);

}

Output of the Rock Paper Scissors Java Game

Please enter your name
Chinmay
Select  ROCK  PAPER SCISSOR
ROCK
Chinmay selected ROCK   computer selected SCISSORS   Chinmay Beats computer You won!
Do you want to play again? y

Select  ROCK  PAPER SCISSOR
Scissor
Chinmay selected SCISSORS   computer selected PAPER   Chinmay Beats computer You won!
Do you want to play again? y

Select  ROCK  PAPER SCISSOR
ROCK
Chinmay selected ROCK   computer selected PAPER   Computer Beats Chinmay You Lost!
Do you want to play again? y

Select  ROCK  PAPER SCISSOR
ROCK
Chinmay selected ROCK   computer selected PAPER   Computer Beats Chinmay You Lost!
Do you want to play again? y

Select  ROCK  PAPER SCISSOR
SCISSORS
Chinmay selected SCISSORS   computer selected SCISSORS   Tie!
Do you want to play again? y

Select  ROCK  PAPER SCISSOR
PAPER
Chinmay selected PAPER   computer selected ROCK   Chinmay Beats computer You won!
Do you want to play again? y

Select  ROCK  PAPER SCISSOR
ROCK
Chinmay selected ROCK   computer selected SCISSORS   Chinmay Beats computer You won!
Do you want to play again? y

Select  ROCK  PAPER SCISSOR
PAPER
Chinmay selected PAPER   computer selected SCISSORS   Computer Beats Chinmay You Lost!
Do you want to play again? y

Select  ROCK  PAPER SCISSOR
ROCK
Chinmay selected ROCK   computer selected SCISSORS   Chinmay Beats computer You won!
Chinmay HAS WON THE GAME.............
Do you want to play again? n
Number of games played is 9
Chinmay's score 5
Computers score 3

Please enter your name

Chinmay

Select ROCK PAPER SCISSOR

ROCK

Chinmay selected ROCK computer selected SCISSORS Chinmay Beats computer You won!

Do you want to play again? y

Select ROCK PAPER SCISSOR

Scissor

Chinmay selected SCISSORS computer selected PAPER Chinmay Beats computer You won!

Do you want to play again? y

Select ROCK PAPER SCISSOR

ROCK

Chinmay selected ROCK computer selected PAPER Computer Beats Chinmay You Lost!

Do you want to play again? y

Select ROCK PAPER SCISSOR

ROCK

Chinmay selected ROCK computer selected PAPER Computer Beats Chinmay You Lost!

Do you want to play again? y

Select ROCK PAPER SCISSOR

SCISSORS

Chinmay selected SCISSORS computer selected SCISSORS Tie!

Do you want to play again? y

Select ROCK PAPER SCISSOR

PAPER

Chinmay selected PAPER computer selected ROCK Chinmay Beats computer You won!

Do you want to play again? y

Select ROCK PAPER SCISSOR

ROCK

Chinmay selected ROCK computer selected SCISSORS Chinmay Beats computer You won!

Do you want to play again? y

Select ROCK PAPER SCISSOR

PAPER

Chinmay selected PAPER computer selected SCISSORS Computer Beats Chinmay You Lost!

Do you want to play again? y

Select ROCK PAPER SCISSOR

ROCK

Chinmay selected ROCK computer selected SCISSORS Chinmay Beats computer You won!

Chinmay HAS WON THE GAME.............

Do you want to play again? n

Number of games played is 9

Chinmay's score 5

Computers score 3

Contact Online Java Tutor for private java classes

Download Java Source Code for Rock Paper Scissor Game

Filed Under: Java

Ejb1 vs Ejb2 vs Ejb3

November 30, 2013 By javatution Leave a Comment

Ejb1 had limited functionality just as a lady bug that doesn’t do much work still is appreciated by people due to its beauty.

Ejb2 was very heavy like the Elephant with functionalities. Still to take proper use of the elephant power it had to be tamed, or Ejb2 was later simplified to Ejb3

Ejb3 is very simple having power and is serving the people very well like a cow giving milk to the universe.

Overview of EJB

Ejb is a platform for building ,reusable, portable and scalable business applications using java.

Ejb helps developers to concentrate on building business logic code without having to build infrastructure code comprising of functionalities including transactions, security, automated persistence that are provided by the Ejb container.

Ejb as Component

Ejbs are server side components that you can use to build parts of an application like business logic or persistence code. These components in Ejb3 are simple POJO with special power. Component means that the user need not know the inner working of the Component, he only needs to know what he has to give and what the Component will give you i.e. application behavior has to be completely encapsulated from the outside world.

There are 3 types of Ejbs. Session beans taking care of business logic. Entity Bean used for persistence. Message driven beans.

One of the most important use of Ejbs is its reusability. E.g. If there is a site for online books that is using an Ejb code for checking credit card. Then if we create another Website for CDs then we can reuse the same credit card Ejb. The first Ejb can be put as an Ejb component or a web service that is used by both applications.

Application1
uses Credit card Ejb

Application2
Ejb as Framework

The Ejb Container houses the Ejb components we develop. This Ejb Container together with the Ejb Component act as a Framework with predefined functionalities. This relieves the programmer from coding certain areas like transaction, security and persistence that are provide by the Ejb Container itself. Like if a programmer is creating a bean related to processing a credit card he need not create coding for the Transaction and Security that is provided by the Ejb Container Automatically.

We can use metadata annotations in our beans to specify what all services and functionalities we require. These are added dynamically when required during deployment. Metadata annotations is a way to specify the properties in a POJO, and these functionalities get automatically added. So we can say a POJO + Metadata annotation=Ejb3 bean. So we don’t need any outside xml configuration files.

Ejb is a specification which is followed by a large group of user vendors creating application server. So all have to follow the same specification making our applications portable.

Domain Driven Design

DDD is the preferred way as compared to the traditional four tired architecture followed by Ejb 2.

Following DDD the domain objects should contain buisness logic and shouldn’t be just a replica of database record. Incase of Ejb 2 beans were not POJOS and didn’t support OO features like inheritance, polymorphism.

Ejb3 helps follow DDD. Beans created using Ejb3 JPA supports polymorphism, inheritance etc.

Why choose EJB 3 among other technologies

Ease of use, Integrated solution stack— Ejb3 offers a complete stack of server solutions, including persistence, dependency injection, interceptors i.e. we won’t need to look for third party solutions to integrate in our application.

Filed Under: Java

Ant Java Build Tool Tutorial

November 23, 2013 By javatution Leave a Comment

Ant is a Java build tool. It is an open source program designed to help develop, and build big programs by automating the work tasks of compiling code, running tests, and Packaging the results for redistribution.

It is written completely in Java there by it is platform independent, easy to use, extensible, and scalable. It can be used in a small personal project, or it can be used in a large, project. It automates the entire build process.

In Ant build files are used to describe how to build a project. In the build file

developers list the high-level goals called the targets and actions to take to achieve each goal called the tasks. Each project contains multiple targets. Targets can depend on other targets. Targets contain tasks and Tasks do the work

Working with ANT

First ANT has to be downloaded and installed in the developers machine. Then the Path of the computer should be set to point to the bin directory of ANT. An environment variable called ANT_HOME should also be made in the System variables pointing to the installation directory of ANT.

A build.xml file should be created that will contain several targets that will further contain different tasks.

1) Target containing Tasks for creating build/classes directory to contain compiled files and creating a dist folder to contain the jar or war file of the project.

2) A Target to compile the java files in the source folder and put it into the build/classes folder.

3) A Target that will package the project to a jar or war file.

4) A Target to create the java docs of the project.

5) A Target to run all the tests on the project.

6) A Target to run the class file containing the main method.

After following the steps the user can simply type ant on the command line and ANT will read the “build.xml” and execute all the targets.

Some of the very important benefits of ANT are as follows:

Ant is free and Open Source. Ant makes it easy to bring developers into a project. It is widely supported. It integrates testing into the build processes and enables continuous integration. It runs inside Integrated Development Environments

Filed Under: Java

Java Exception Handling – How to Handle Exceptions in Java – JavaTutorOnline

November 23, 2013 By javatution 8 Comments

What are Exceptions in Java?

An Exception in java is an object that describes an exceptional condition in the program. A java exception object may be either generated in the code manually or automatically by the java run time system.

Java Exception Hierarchy

All types of java exceptions are subclass of the inbuilt class Throwable. The two sub classes of Throwable are Exception and Error. The branch Exception deals with those exceptional conditions that the user program should handle. Exception further branches into RunTimeException and Checked Exceptions. RuntimeExceptions are those exceptions that are automatically defined for the programs that we write, like ArithmeticException, NullPointerException etc. The other branch is Error, which defines exceptions that are not expected to be handled by our program.

A java program passes through compile time and run time. Exceptions are run time errors.

Exception is an inbuilt class in the java.lang package. There are many sub classes of Exception class like ArithmeticException, NullpointerException etc.

Depending upon the nature of the problem occurring during run time, java creates the appropriate Exception object and throws it.

For example: int i = 1/0; [Java will throw ArithmeticException type of object]

Why do we need to do Java Exception handling?

Java’s Default exception handlers doesn’t do the work properly, they stop the program execution abruptly and gives a weird output to the user. This is the reason why we should do exception handling. To do java exception handling we have to use try and catch blocks. The lines of code that may throw some exception should be put in the try block and whatever we want to be done should be put in to the catch block.

public class Exception_Demo {
public static void main(String[] args) {
int i = 1 / 0;
System.out.println("After division by 0");
}
}

public class Exception_Demo {

public static void main(String[] args) {

int i = 1 / 0;

System.out.println("After division by 0");

}

Here, by doing 1/0, our program will stop abruptly. And it will give a weird error message. Like,

Exception in thread “main” java.lang.ArithmeticException: / by zero
at Exception_Demo.main(Exception_Demo.java:6)

But on using try and catch the problem is overcome.

Try Catch Block in Java Exception Handling

Try Block– Those code that may lead to exceptions during run time are generally put inside the try block.
Catch Block– What ever we want to do when ever any exception occurs should be put in the catch block.

public class Try_Catch {
public static void main(String[] args) {
try {
int i = 1 / 0;
System.out.println("After division");
} catch (Exception e) {
System.out.println("Division by 0");
e.printStackTrace();
}
System.out.println("After try catch");
}
}

public class Try_Catch {

public static void main(String[] args) {

try {

int i = 1 / 0;

System.out.println("After division");

} catch (Exception e) {

System.out.println("Division by 0");

e.printStackTrace();

}

System.out.println("After try catch");

}

Due to the use of try catch block the above program will not stop abruptly, rather it will give a customized exception message during run time.

Division by 0
java.lang.ArithmeticException: / by zero
at Try_Catch.main(Try_Catch.java:8)
After try catch

Division by 0

java.lang.ArithmeticException: / by zero

at Try_Catch.main(Try_Catch.java:8)

After try catch

Multiple catch blocks

There are many sub classes of the class Exception like ArithmeticException, NullPointerException etc. During run time different type of exception may occur depending on different conditions. So to handle the problems differently in different circumstances we need to have multiple catch blocks.

public class Multi_Catch {
public static void main(String[] args) {
try {
int len = args.length;
if (len == 0) {
int i = 1 / 0;
}
if (len == 1) {
int j[] = new int[3];
j[10] = 4343;
}
} catch (ArithmeticException e) {
System.out.println("you have not " +
"entered any argument");
} catch (ArrayIndexOutOfBoundsException e) {
// TODO: handle exception
} catch (Exception e) {
// TODO: handle exception
}
}
}

public class Multi_Catch {

public static void main(String[] args) {

try {

int len = args.length;

if (len == 0) {

int i = 1 / 0;

}

if (len == 1) {

int j[] = new int[3];

j[10] = 4343;

}

} catch (ArithmeticException e) {

System.out.println("you have not " +

"entered any argument");

} catch (ArrayIndexOutOfBoundsException e) {

// TODO: handle exception

} catch (Exception e) {

// TODO: handle exception

}

In this example, if length is 0 than it will be caught by catch block handling ArithmeticException. If we go out of the range of the array an ArryIndexOutOfBoundException is thrown. Programs may have various type of exceptions which can be handled through multiple catch blocks. In this example third catch block is for general Exception type. The general Exception catch block should be put at the end.

How to Create Custom Exception Class?

There are some situations that is not an exception for java but it is an exception for our project. For example if you want to run your program only when user gives commandline input (this is your program need which is not an exception for java) so, this is the time when we manually create our own exception class. To create a custom exception we have to extent the inbuilt Exception class.

public class No_Commandline_Exception extends Exception {

}

public class No_Commandline_Exception extends Exception {

}

Throw Keyword

Throw keyword is used for manually throwing java exception objects.

public class Throw_Demo {
// throw keyword is used for manually throw exception object
public static void main(String[] args) {
No_Commandline_Exception obj =
new No_Commandline_Exception();
try {
throw obj;
} catch (No_Commandline_Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

public class Throw_Demo {

// throw keyword is used for manually throw exception object

public static void main(String[] args) {

No_Commandline_Exception obj =

new No_Commandline_Exception();

try {

throw obj;

} catch (No_Commandline_Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

When a custom exception object is thrown it has to be handled through try and catch blocks because it cannot be handled by the default exception handler of java.

Throws Keyword

When we define a function and we don’t want to put try and catch block than we can use throws keyword. The caller of the function has to put the try and catch blocks. Throws keyword is for delegating the exception handling mechanism to the caller of the function.

eg.

static void fun() throws No_Commandline_Exception,ArithmeticException

1	static void fun() throws No_Commandline_Exception,ArithmeticException

Checked and unchecked exception

Unchecked exceptions are those exceptions that can be handling by java’s default exception handlers. If we try to throw unchecked exception inside a function we don’t need to put try and catch block nor the throws.

Checked exceptions are those exceptions that can’t handle by java’s default exception handlers.
When a checked exception is thrown from inside a function we are bound to put the try and catch block or the throws declaration.

List of checked exceptions

Exception	Description
ClassNotFoundException	Class not found
CloneNotSupportedException	Attempt to clone an object that does not implement the Cloneable interface
IllegalAccessException	Access to a class is denied
InstantiationException	Attempt to create an object of an abstract class or interface
InterruptedException	One thread has been interrupted by another thread
NoSuchFieldException	A requested field does not exist
NoSuchMethodException	A requested method does not exist

List of unchecked exceptions

Exception	Description
ArithmeticException	Arithmetic error, such as divide-by-zero
ArrayIndexOutOfBoundsException	Array index is out-of-bounds
ArrayStoreException	Assignment to an array element of an incompatible type
ClassCastException	Invalid cast
IllegalArgumentException	Illegal argument used to invoke a method
IllegalMonitorStateException	Illegal monitor operation, such as waiting on an unlocked thread
IllegalStateException	Environment or application is in incorrect state
IllegalThreadStateException	Requested operation not compatible with current thread state
IndexOutOfBoundsException	Some type of index is out-of-bounds
NegativeArraySizeException	Array created with a negative size
NullPointerException	Invalid use of a null reference
NumberFormatException	Invalid conversion of a string to a numeric format
SecurityException	Attempt to violate security
StringIndexOutOfBounds	Attempt to index outside the bounds of a string
UnsupportedOperationException	An unsupported operation was encountered

Filed Under: Java

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Mr Chinmay Patel

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