Java泛型(10)：泛型与异常

由于擦除的原因，将泛型运用于异常是非常受限的。catch语句不能捕获泛型类型的异常，因为在编译期和运行期都必须知道异常的确切类型。但是，类型参数可能会在一个方法的throw子句中用到。这使得你可以编写随检查型异常的类型而发生变化的泛型代码。请看下面的例子。

 

interface Processor<T,E extends Exception> {
    void process(List<T> resultCollector) throws E;
}

class ProcessRunner<T,E extends Exception> extends ArrayList<Processor<T,E>> {
    List<T> processAll() throws E {
        List<T> resultCollector = new ArrayList<T>();
        for(Processor<T,E> processor : this)
            processor.process(resultCollector);
        return resultCollector;
    }
}

class Failure1 extends Exception {}

class Processor1 implements Processor<String,Failure1> {
    static int count = 3;
    public void process(List<String> resultCollector) throws Failure1 {
        if(count-- > 1)
            resultCollector.add("Hep!");
        else
            resultCollector.add("Ho!");
        if(count < 0)
            throw new Failure1();
    }
}

class Failure2 extends Exception {}

class Processor2 implements Processor<Integer,Failure2> {
    static int count = 2;
    public void process(List<Integer> resultCollector) throws Failure2 {
        if(count-- == 0)
            resultCollector.add(47);
        else {
            resultCollector.add(11);
        }
        if(count < 0)
            throw new Failure2();
    }
}

public class ThrowGenericException {
    public static void main(String[] args) {
        ProcessRunner<String,Failure1> runner = new ProcessRunner<>();
        for(int i = 0; i < 3; i++)
            runner.add(new Processor1());
        try {
            System.out.println(runner.processAll()); // [Hep!, Hep!, Ho!]
        } catch(Failure1 e) {
            System.out.println(e);
        }
        ProcessRunner<Integer,Failure2> runner2 = new ProcessRunner<>();
        for(int i = 0; i < 3; i++)
            runner2.add(new Processor2());
        try {
            System.out.println(runner2.processAll());
        } catch(Failure2 e) {
            System.out.println(e); // chapter15.class14.Failure2
        }
    }
}