Java Exception Propagation

In Java, Exception propagation is the mechanism by which an exception that is raised in a method is passed on to the calling method.

When a method encounters an exception, it can handle the exception within the method or throw the exception to the calling method using the throw statement.

If the method throws a checked exception, it must either catch the exception or declare the exception in its method signature using the throws keyword.

Here’s an example of exception propagation in Java:

public void method1() throws Exception {
    // some code that may throw an exception
    throw new Exception("Exception in method1");
}

public void method2() {
    try {
        method1();
    } catch(Exception e) {
        // handle the exception here
    }
}

In this example, method1 declares that it may throw an exception using the throws keyword. When method2 calls method1, it must either catch the exception or declare it in its method signature. In this case, method2 catches the exception and handles it. If method2 did not catch the exception, the exception would be propagated up the call stack to the calling method, and so on, until the exception is either caught or the program terminates.

Exception Propagation Example:

Here’s an example of exception propagation in Java:

public class ExceptionPropagationExample {
    public static void main(String[] args) {
        try {
            divide(10, 0);
        } catch (Exception e) {
            System.out.println("Exception caught: " + e.getMessage());
        }
    }

    public static int divide(int a, int b) throws Exception {
        int result = 0;
        if (b == 0) {
            throw new Exception("Cannot divide by zero");
        } else {
            result = a / b;
        }
        return result;
    }
}

In this example, the divide method takes two integers as arguments and throws an exception if the second argument is zero. The main method calls divide with the arguments 10 and 0, which causes an exception to be thrown.

Since divide declares that it may throw an exception using the throws keyword, main either needs to catch the exception or declare it in its method signature. In this case, main catches the exception and prints a message.

If main did not catch the exception, it would be propagated up the call stack to the JVM, which would terminate the program and print an error message.