throws keyword

Throws statement

 In our program, if there is any chance of raising checked exception compulsory we should handle either by try-catch or by throws keyword otherwise the code won’t compile.

Example:

  class Test3

      {

           public static void main(String[] args){

           Thread.sleep(5000);

               }

       }

• Unreported exception java.lang.InterruptedException; must be caught or declared to be thrown. We can handle this compile-time error by using the following 2 ways. 

Example:

• Hence the main objective of the “throws” keyword is too delicate the responsibility of exception handling to the caller method.

• “throws” keyword required only checked exceptions. Usage of throws for unchecked exceptions there is no use.

• “throws” keyword required only to convenes complier. The usage of throws keyword doesn’t prevent abnormal termination of the program. 

Example:

     class Test

          {

              public static void main(String[] args)throws InterruptedException{

              doStuff();

          }

             public static void doStuff()throws InterruptedException{

            doMoreStuff();

        }

             public static void doMoreStuff()throws InterruptedException{

             Thread.sleep(5000);

         }

     }

Output:

Compile and running successfully.

• In the above program if we are removing at least one throws keyword then the program

won’t compile.

Case 1: we can use throws keyword only for Throwable types otherwise we will get a compile-time error saying incompatible types. 

Example: 

Case 2: 

Example: 

Case 3:

• In our program, if there is no chance of raising an exception then we can’t right catch block for that exception otherwise, we will get a compile-time error saying exception XXX is never thrown in the body of the corresponding try statement. But this rule is applicable only for fully checked exceptions.

Example: