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。

 1 interface Processor<T,E extends Exception> {
 2     void process(List<T> resultCollector) throws E;
 3 }
 4 
 5 class ProcessRunner<T,E extends Exception> extends ArrayList<Processor<T,E>> {
 6     List<T> processAll() throws E {
 7         List<T> resultCollector = new ArrayList<T>();
 8         for(Processor<T,E> processor : this)
 9             processor.process(resultCollector);
10         return resultCollector;
11     }
12 }
13 
14 class Failure1 extends Exception {}
15 
16 class Processor1 implements Processor<String,Failure1> {
17     static int count = 3;
18     public void process(List<String> resultCollector) throws Failure1 {
19         if(count-- > 1)
20             resultCollector.add("Hep!");
21         else
22             resultCollector.add("Ho!");
23         if(count < 0)
24             throw new Failure1();
25     }
26 }
27 
28 class Failure2 extends Exception {}
29 
30 class Processor2 implements Processor<Integer,Failure2> {
31     static int count = 2;
32     public void process(List<Integer> resultCollector) throws Failure2 {
33         if(count-- == 0)
34             resultCollector.add(47);
35         else {
36             resultCollector.add(11);
37         }
38         if(count < 0)
39             throw new Failure2();
40     }
41 }
42 
43 public class ThrowGenericException {
44     public static void main(String[] args) {
45         ProcessRunner<String,Failure1> runner = new ProcessRunner<>();
46         for(int i = 0; i < 3; i++)
47             runner.add(new Processor1());
48         try {
49             System.out.println(runner.processAll()); // [Hep!, Hep!, Ho!]
50         } catch(Failure1 e) {
51             System.out.println(e);
52         }
53         ProcessRunner<Integer,Failure2> runner2 = new ProcessRunner<>();
54         for(int i = 0; i < 3; i++)
55             runner2.add(new Processor2());
56         try {
57             System.out.println(runner2.processAll());
58         } catch(Failure2 e) {
59             System.out.println(e); // chapter15.class14.Failure2
60         }
61     }
62 }