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
         }
     }
 }