What Happens if an Exception is Not Caught

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An uncaught exception results in the uncaughtException() method of the thread’s ThreadGroup being invoked, which eventually results in the termination of the program in which it is thrown.

In Java, if an exception is not caught (handled) by an appropriate exception handler, it will propagate up the call stack. This process is known as “propagation of exceptions.” Here’s what happens:

  1. Propagation through method calls:
    • If a method does not catch an exception, it will propagate the exception to the calling method.
    • The calling method has two options: catch the exception using a try-catch block or propagate the exception further up.
  2. Propagation through the call stack:
    • If the exception is not caught by any method in the call stack, it will eventually reach the top level of the call stack (usually the main method in the case of a standalone Java application or the entry point of a servlet or JSP in a web application).
  3. Default Exception Handling:
    • If the exception is not caught anywhere in the call stack, the Java Virtual Machine (JVM) provides default exception handling.
    • The default exception handling typically involves printing information about the exception (including its type, message, and stack trace) to the console, and the program terminates.

Here’s an example to illustrate:

java
public class ExceptionExample {
public static void main(String[] args) {
try {
// Some code that may throw an exception
int result = 5 / 0; // This will throw an ArithmeticException
System.out.println("Result: " + result); // This line will not be reached
} catch (ArithmeticException e) {
// This block will catch the exception
System.out.println("Caught exception: " + e.getMessage());
}// Code here will continue executing if the exception is caught
System.out.println(“Program continues…”);
}
}

In this example, the catch block handles the ArithmeticException. If the exception was not caught, it would propagate up and eventually lead to default exception handling by the JVM.