// exceptions/StormyInning.java // (c)2017 MindView LLC: see Copyright.txt // We make no guarantees that this code is fit for any purpose. // Visit http://OnJava8.com for more book information. // Overridden methods can throw only the exceptions // specified in their base-class versions, or exceptions // derived from the base-class exceptions class BaseballException extends Exception {} class Foul extends BaseballException {} class Strike extends BaseballException {} abstract class Inning { Inning() throws BaseballException {} public void event() throws BaseballException { // Doesn't actually have to throw anything } public abstract void atBat() throws Strike, Foul; public void walk() {} // Throws no checked exceptions } class StormException extends Exception {} class RainedOut extends StormException {} class PopFoul extends Foul {} interface Storm { void event() throws RainedOut; void rainHard() throws RainedOut; } public class StormyInning extends Inning implements Storm { // OK to add new exceptions for constructors, but you // must deal with the base constructor exceptions: public StormyInning() throws RainedOut, BaseballException {} public StormyInning(String s) throws BaseballException {} // Regular methods must conform to base class: //- void walk() throws PopFoul {} //Compile error // Interface CANNOT add exceptions to existing // methods from the base class: //- public void event() throws RainedOut {} // If the method doesn't already exist in the // base class, the exception is OK: @Override public void rainHard() throws RainedOut {} // You can choose to not throw any exceptions, // even if the base version does: @Override public void event() {} // Overridden methods can throw inherited exceptions: @Override public void atBat() throws PopFoul {} public static void main(String[] args) { try { StormyInning si = new StormyInning(); si.atBat(); } catch(PopFoul e) { System.out.println("Pop foul"); } catch(RainedOut e) { System.out.println("Rained out"); } catch(BaseballException e) { System.out.println("Generic baseball exception"); } // Strike not thrown in derived version. try { // What happens if you upcast? Inning i = new StormyInning(); i.atBat(); // You must catch the exceptions from the // base-class version of the method: } catch(Strike e) { System.out.println("Strike"); } catch(Foul e) { System.out.println("Foul"); } catch(RainedOut e) { System.out.println("Rained out"); } catch(BaseballException e) { System.out.println("Generic baseball exception"); } } }