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Difference between Throw and Throws

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Difference between Throw and Throws
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‘Throw’ and ‘throws’ would seem similar in general life having a difference of tenses only. However, in the programming language, Java, these two are very different from each other and used to do various tasks. Throw and Throws are keywords in java used in exception handling.

Use of Throw and Throws in Java

The ‘Throw’ keyword is used to give an instance of exception that the programmer has manually created to JVM whereas the ‘throws’ keyword is used to give the responsibilities of exception handling, occurred in the method to the caller method.

Syntax-wise: In throw instance of exception is defined in the exception block/ class. In Throws the throw keyword is followed by the exception class

Throw vs Throws in Java

THROW

THROWS

A throw is used to throw an exception explicitly

A throws to declare one or more exceptions, separated by commas.

Can throw a single exception using throw

Multiple can be thrown using Throws

This keyword is used in the method

Signature method is used with keyword throws

Only unchecked exceptions propagated using throw keyword.

To raise an exception throws keyword followed by the class name and checked exception can be propagated.

Throw keyword is followed by the instance variable

Throws keyword is followed by the exception class

What is Throw in Java

Throw keyword in java is used to throw an exception explicitly and logically defined by the programmer during the program control moves from one block to another assuming the errors exception are defined and handled accordingly.

Throw Syntax

syntax  of throw :-  throw <instance>;

Throw Example in Java

void mtod (){
throw new mathsexception(“we are sorry there is no solution”);
}

Program :
public class ThrowExample{ 

   void Votingage(int age){ 
                   if(age<18) 
                      throw new ArithmeticException("you can't vote as not Eligible to  vote"); 
                   else 
                      System.out.println("Eligible for voting"); 
   } 
   public static void main(String args[]){ 
                   ThrowExample obj = new ThrowExample();
                   obj.Votingage(13); 
                   System.out.println("End Of Program"); 
   } 
}

OUTPUT 

$java -Xmx128M -Xms16M ThrowExample
Exception in thread "main" java.lang.ArithmeticException: you can't vote as not Eligible to  vote  at ThrowExample.Votingage(ThrowExample.java:5)  at ThrowExample.main(ThrowExample.java:11)

What is Throws in Java?

Throws: is used to declare and call an exception block, which means its working is similar to the try-catch block.

Throws Example in Java

public class ThrowsExample{ 
   int divion(int a, int b) throws ArithmeticException{ 
                int intet = a/b;
                return intet;
   } 
   public static void main(String args[]){ 
                ThrowsExample obj = new ThrowsExample();
                try{
                   System.out.println(obj.divion(15,0)); 
                }
                catch(ArithmeticException e){
                   System.out.println("Division cannot be done using ZERO");
                }

   } 

}

Output 

$java -Xmx128M -Xms16M ThrowsExample
Division cannot be done using ZERO 

Key difference between Throws and Throw in Java 

✓ The basic difference between these two terms is that ‘throws’ keyword uses the name of the exception classes where the ‘throw’ keyword uses the exception object.

✓The ‘throw’ keyword can throw only one i.e. a single exception instance. On the other hand, throws keyword can throw multiple exception classes and separate by a comma.

✓The ‘throw’ keyword is used to simply throw an exception where ‘throws’ keyword is used for declaration of exception, which indicates the exception that is thrown by the method.

✓The ‘throw’ keyword could be utilised inside method or static block initializer. The ‘throws,’ on the other hand, could only be used in method declaration.

✓The ‘throw’ keyword is unable to propagate the unchecked exception to the calling method where ‘throws’ keyword is used to propagate exception to the calling method. However, unchecked exception could be propagated by using throw keyword word.

✓Another basis for the difference between the two is syntax. The syntax of ‘throw’ is followed by an instance variable but syntax of ‘throws’ is followed by the exception class names.

✓’Throw’ keyword is used within the method where ‘throws’ keyword is used with the method signature.


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