stormyinning.java

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//: StormyInning.java
// Overridden methods may throw obly the exceptions specified in their base-class verions,

class BaseballException extends Exception {}
class Foul extends BaseballException {}
class Strike extends BaseballException {}

abstract class Inning {
	Inning() throws BaseballException {}
	void event() throws BaseballException {
		//	Doesn't actually have to throw anything
	}
	abstract void atBat() throws Strike, Foul;
	void walk() {}	//	Throws nothing
}

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:
	StormyInning() throws RainedOut, BaseballException {}
	StormyInning(String s) throws Foul, BaseballException {}
	//	Regular methods must conform the 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:
	public void rainHard() throws RainedOut {}
	//	You can choose to not throw any exceptions, even if base version does:
	public void event() {}
	//	Overridden methods can throw inherited exceptions:
	void atBat() throws PopFoul {}
	public static void min(String[] args) {
		try {
			StormyInning si = new StormyInning();
			si.atBat();
		} catch (PopFoul e) {
		} catch (RainedOut e) {
		} catch (BaseballException e) {}
		//	Strike not thrown in derived version.
		try {
			//	What happends 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) {
		} catch (Foul e) {
		} catch (RainedOut e) {
		} catch (BaseballException e) {}
	}
}