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 goes down the call stack to the previous method to handle the exception this is known as Exception propagation

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class ExceptonPropagation {
   public static void method2() throws FileNotFoundException, IOException {
       BufferedReader br = new BufferedReader(new FileReader("test.txt"));
       String s = br.readLine();
   }

   public static void method1() {
       try {
           method2();
       } catch (IOException e) {
           e.printStackTrace();
       }
   }
   public static void main(String[] args) {
       method1();
   }
}

here from method2 we are propagating the FileNotFoundException and IOException to its calling method1 where method1 is handling these 2 exceptions