实现的方法中，抛的异常只能比父类或接口中的少（转）

实现的方法中，抛的异常只能比父类或接口中的少

import java.io.IOException;

public interface IHello {
    void say(String msg) throws TestException, IOException;
}

class IHelloImpl implements IHello {

    @Override
    public void say(String msg) throws IOException {
        System.out.println("msg = [" + msg + "]");
    }
}

类StormyInning既扩展了基类Inning，又实现了接口Storm，而且基类Inning和接口Storm都声明了方法event()：

package com.liush.chapter12;

//Overridden methods may 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 {

    public Inning() throws BaseballException {}

    public void event() throws BaseballException {

        // Doesen't actually have to throw anthing

    }

    public abstract void atBat() throws Strike,Foul;

    public void walk() {} //Throws no checked exceptions

}

class StormException extends Exception {}

class RainedOut extends StormException {}

class EventException extends StormException {}

class PopFoul extends Foul {}

interface Storm{

    public void event() throws EventException;

    public void rainHard() throws RainedOut;

}

public class StormyInning extends Inning implements Storm{

    //OK to add new exceptions for constructor, but you must

    //deal with the base constructor exceptions:

    public StormyInning() throws RainedOut,BaseballException {}

    public StormyInning(String s) throws Foul,BaseballException {}

    @Override

    public void rainHard() throws RainedOut {

        // TODO Auto-generated method stub

    }

    public void event() {System.out.println("Override the Inning.");}

    @Override

    public void atBat() throws Strike, Foul {

        // TODO Auto-generated method stub

    }

    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");}

        try{

            Inning i = new StormyInning();

            Storm k=new StormyInning();

            i.event();

            k.event();

            i.atBat();

        }

        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");}

        catch (EventException e) {    // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

}

说明：类StormyInning既继承了Inning基类，又实现了Storm接口，用基类来建立StormyInning对象时，根据向上转型，event()是被认为是从Inning中来：

而用接口Storm来建立StormyInning对象时，event()则是被认为是从Sorm中来的：

因此，它们抛出异常就决定于它们的基类和接口了：

http://blog.163.com/liu_sheng_han/blog/static/190591372201212394856740/