Exception Restrictions when Overriding

When you extend a class and override a method, Java insists that the new method cannot be declared as throwing checked exceptions of classes other than those that were declared by the original method (in the base class). It may, however, throw exceptions derived from the base-class exceptions. This is a useful restriction, since it means that code that works with the base class will automatically work with any object derived from the base class (a fundamental OOP concept, of course), including exceptions.

This example demonstrates the kinds of restrictions imposed (at compile-time) for exceptions:

 public class Base {   public void f() throws IOException {   }}public class LegalOne extends Base {   public void f() throws IOException {   /* Overridden method throws the same _exception as in the base-classversion, hence legal. */   }}public class LegalTwo extends Base {   public void f() throws IOException, _MalformedURLException {   /* MalformedURLException is derived from _IOException, hence it is legalto throw this exception in f(). */   }}public class IllegalOne extends Base   public void f() throws IOException, _IllegalAccessException {   /* IllegalAccessException is not derived _from IOException; in fact, itis the super class of IOException. Hence this _method declaration isillegal, since overridden methods can only throw _either the base-classexceptions or exceptions derived from the base-class _exceptions. */   }}public class IllegalTwo extends Base   public void f() throws Exception {   /* Exception is the super-class of IOException, _hence illegal, asexplained above. */   }}
Share the Post:
Share on facebook
Share on twitter
Share on linkedin


The Latest

your company's audio

4 Areas of Your Company Where Your Audio Really Matters

Your company probably relies on audio more than you realize. Whether you’re creating a spoken text message to a colleague or giving a speech, you want your audio to shine. Otherwise, you could cause avoidable friction points and potentially hurt your brand reputation. For example, let’s say you create a

chrome os developer mode

How to Turn on Chrome OS Developer Mode

Google’s Chrome OS is a popular operating system that is widely used on Chromebooks and other devices. While it is designed to be simple and user-friendly, there are times when users may want to access additional features and functionality. One way to do this is by turning on Chrome OS

homes in the real estate industry

Exploring the Latest Tech Trends Impacting the Real Estate Industry

The real estate industry is changing thanks to the newest technological advancements. These new developments — from blockchain and AI to virtual reality and 3D printing — are poised to change how we buy and sell homes. Real estate brokers, buyers, sellers, wholesale real estate professionals, fix and flippers, and beyond may