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Difference between throw and throws in java

By | Filed Under: Exception Handling

In this guide, we will discuss the difference between throw and throws keywords. Before going though the difference, refer my previous tutorials about throw and throws.

Throw vs Throws in java

1. Throws clause is used to declare an exception, which means it works similar to the try-catch block. On the other hand throw keyword is used to throw an exception explicitly.

2. If we see syntax wise than throw is followed by an instance of Exception class and throws is followed by exception class names.
For example:

throw new ArithmeticException("Arithmetic Exception");

and

throws ArithmeticException;

3. Throw keyword is used in the method body to throw an exception, while throws is used in method signature to declare the exceptions that can occur in the statements present in the method.

For example:
Throw:

...
void myMethod() {
   try {
      //throwing arithmetic exception using throw
      throw new ArithmeticException("Something went wrong!!");
   } 
   catch (Exception exp) {
      System.out.println("Error: "+exp.getMessage());
   }
}
...

Throws:

...
//Declaring arithmetic exception using throws
void sample() throws ArithmeticException{
   //Statements
}
...

4. You can throw one exception at a time but you can handle multiple exceptions by declaring them using throws keyword.
For example:
Throw:

void myMethod() {
   //Throwing single exception using throw
   throw new ArithmeticException("An integer should not be divided by zero!!");
}
..

Throws:

//Declaring multiple exceptions using throws
void myMethod() throws ArithmeticException, NullPointerException{
   //Statements where exception might occur
}

These were the main differences between throw and throws in Java. Lets see complete examples of throw and throws keywords.

Throw Example

To understand this example you should know what is throw keyword and how it works, refer this guide: throw keyword in java.

public class Example1{  
   void checkAge(int age){  
	if(age<18)  
	   throw new ArithmeticException("Not Eligible for voting");  
	else  
	   System.out.println("Eligible for voting");  
   }  
   public static void main(String args[]){  
	Example1 obj = new Example1();
	obj.checkAge(13);  
	System.out.println("End Of Program");  
   }  
}

Output:

Exception in thread "main" java.lang.ArithmeticException: 
Not Eligible for voting
at Example1.checkAge(Example1.java:4)
at Example1.main(Example1.java:10)

Throws Example

To understand this example you should know what is throws clause and how it is used in method declaration for exception handling, refer this guide: throws in java.

public class Example1{  
   int division(int a, int b) throws ArithmeticException{  
	int t = a/b;
	return t;
   }  
   public static void main(String args[]){  
	Example1 obj = new Example1();
	try{
	   System.out.println(obj.division(15,0));  
	}
	catch(ArithmeticException e){
	   System.out.println("You shouldn't divide number by zero");
	}
   }  
}

Output:

You shouldn't divide number by zero
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Comments

    • Hi Prahalad, Could you please let me know in which part you faced difficulties to understand? Try to go through the separate articles of throw keyword and throws clause and then go through the differences, you will be able to understand better then. Thanks!

      Reply

    • By using Throw keyword in java you cannot throw more than one exception but using throws you can declare multiple exceptions.
      I hope this solves your confusion.

      Reply

  2. You should have explained the flow of execution when any program is given as a supporting example, that would make things easier and comfortable

    Reply

    • Actually the usage of throw and throws is completely different. It depends whether you are throwing an exception or handling it. To throw an exception we use throw keyword while to handle (catch) an exception we use throws clause.

      Reply

    • Actually Throws keyword is used to throw the checked exceptions which a programmer doesn’t want to handle it so a programmer throws these exception so that compiler did not give an error but throw keyword is used to throw an built-in-exception or user defined exception explicitly so both concepts are different so go through these concepts separately and then read these differences then you will did not get any confusion.

      Reply

  8. Iam not getting why we use new keyword with throw……why there is need for this declaration?
    can any1 explain me?

    Reply

  11. sir , if we can handle all the exception by mentioning THROWS key word in main() method, then whats the use of throw, or why should we go individually to all the methods.?

    Reply

  12. in above comment u r saying “To throw an exception we use throw keyword while to handle (catch) an exception we use throws clause.”,but can u explain me 1 doubt ,although throw is an explicit creator,but still we have to handle that exception or that method using try catch where in that method we write throw new any …exception.

    and when we using throws clause that time also we have to handle that exception or method throwing an exception.

    that means in BOTH cases we are HANDLING the exception,is it right or not?

    Reply

  13. how can we handle the exceptions without using catch,throw, and throws clause.
    I faced this question in one interview. kindly reply me….

    Reply

  15. hi sir, can u send still more java interview questions so that we will easy to face the any interviews.thanq…………

    Reply

    • I have provided the links of the detailed articles of throw and throws keyword at the beginning of this post. Please refer them and let me know if you have any questions.

      Reply

    • Error is a compile time error it may be syntax error or else.. But exception occurs during the execution time it cannot get identified by compiler.

      Reply

  19. class A{
    public void add()throws IOException
    {
    …….
    }
    class B extends A
    {
    public void add()throws Exception
    {
    ………….
    }
    }
    can we take like this?
    please explain me if we take like this what happen I faced this question in one interview.

    Reply

    • @Hemavati, The program you written above is not possible because
      in ur prgrm the add() method is overrided right… Then overrided method should not change its declaration in any sub classes.. der Add() method id declared with the diff exception classes so it cannot possible…(throws different Exception ).

      But…
      We can declare different Exception with method body… only when Superclass method is having super Exception class and subclass has subclass of exception,,

      in your program Exception is super class and the IOexception is Sub class of Exception… hence Your program can rewritten like…

      class A{
      public void add()throws Exception
      {
      …….
      }
      class B extends A
      {
      public void add()throws IOException
      {
      ………….
      }
      }

      Hope you got my msg….

      Reply

  20. Is it possible to handle the exception without using try-catch block and throws?..i am so confused bz this question was asked by interviewer….please help me.

    Reply

  21. One more difference between throws and throw?
    Throw is associated with try-catch block whereas throws is declared with method declaration..
    if there is any mistakes…please respond me..thanks

    Reply

  26. I want to execute a few stmts (lets say stmt1,stmt2) which raise a checked exception(lets say BadException1). I want to execute stmt3,stmt4 no matter whether stmt1 and stmt2 fail or not. Also stmt3,stmt4 throws checked exception BadException2. Write a code block to demonstrate how you will ensure this.

    Reply

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