Question

What is exception propagation?

Give an example of a class that contains at least two methods, in which one method calls another. Ensure that the subordinate method will call a predefined Java method that can throw a checked exception. The subordinate method should not catch the exception.

Explain how exception propagation will occur in your example.

Answer 1

An exception is first thrown from the top of the stack and if it is not caught, it drops down the call stack to the previous method,If not caught there, the exception again drops down to the previous method, and so on until they are caught or until they reach the very bottom of the call stack.This is called exception propagation.

class TestExceptionPropagation{  

  void m(){  

    int data=50/0;  

  }  

  void n(){  

    m();  

  }  

  void p(){  

   try{  

    n();  

   }catch(Exception e){System.out.println("exception handled");}  

  }  

  public static void main(String args[]){  

   TestExceptionPropagation1 obj=new TestExceptionPropagation1();  

   obj.p();  

   System.out.println("normal flow...");  

  }  

}  

Explanation:

In the above example exception occurs in m() method where it is not handled,so it is propagated to previous n() method where it is not handled, again it is propagated to p() method where exception is handled.