日期:2014-05-20 浏览次数:21059 次
private <T> List<T> cashFutures(List<Future<T>> futures) { List<T> values = new ArrayList<T>(); for (Future<T> future : futures) { try { values.add(future.get()); } catch (Exception e) { throw new IllegalStateException(e); } } return values; }
import java.util.*; class Fruit { public String toString() { return "Fruit"; } } class Apple extends Fruit { public String toString(){ return "Apple"; } } class Person { public String toString(){ return "Person"; } } class ClassName<T> {//主类,把你文件名改成ClassName.java void show_1(T t){ System.out.println("show_1 "+ t.toString()); } <E> void show_2(E e){ System.out.println("show_2 "+e.toString()); } <T> void show_3(T t){ System.out.println("show_3 "+t.toString()); } public static void main(String[] args) { ClassName<Fruit> o = new ClassName<Fruit>(); Fruit f = new Fruit(); Apple a = new Apple(); Person p = new Person(); System.out.println("show_1 演示________________________"); o.show_1( f ); o.show_1( a ); // o.show_1( p ); 楼主把这行代码去掉注释看一下,是不能编译通过的。因为在 // ClassName<Fruit>中已经限定了全局的T为Fruit,所以不能再加入Person; System.out.println("show_2 演示________________________"); o.show_2( f ); o.show_2( a ); o.show_2( p ); System.out.println("show_3 演示________________________"); o.show_3( f ); o.show_3( a ); o.show_3( p ); } } [color=#800080]程序输出: show_1 演示________________________ show_1 Fruit show_1 Apple show_2 演示________________________ show_2 Fruit show_2 Apple show_2 Person show_3 演示________________________ show_3 Fruit show_3 Apple show_3 Person[/color]