How does exception handling work in Java?

Throwable has two main branches. Error covers serious JVM-level problems such as OutOfMemoryError and StackOverflowError, which applications normally cannot recover from. Exception covers application-level failures, and RuntimeException marks the unchecked branch.

try {
    int result = Integer.parseInt(input);
    System.out.println(result);
} catch (NumberFormatException error) {
    System.out.println("Invalid number: " + error.getMessage());
} finally {
    System.out.println("done");
}

Good handling practice

• Catch the most specific exception you can handle
• Do not swallow an exception or leave an empty catch block
• Wrap lower-level exceptions and preserve the cause
• Use multi-catch when several exceptions share the same handling
• Avoid using exceptions for ordinary control flow

A stack trace is expensive because it captures the call stack. Throwing in a tight loop for expected conditions hurts performance and obscures intent. Validate inputs and return a result type when absence is normal; reserve exceptions for exceptional conditions.