Java 通配符泛型例子

请看下面的代码，其中会发生错误的代码已经注释掉，并且写明了错误类型

总体来说，泛型通配符就是为了支持多态时父子类，接口扩展类之间的相互转换而生

[java] view plaincopyprint?

package test;

import java.util.ArrayList;

import java.util.List;

publicclass GenericTester {

publicstaticvoid main(String[] args){

GenericTester genericTester=new GenericTester();

List<TestA> list=new ArrayList<GenericTester.TestA>();

GenericTester.TestA tester=genericTester.new TestA();

list.add(tester);

TryGeneric1(list);

TryGeneric2(list);

// TryGeneric3(list); has compile error

// TryGeneric4(list); has compile error

}

privateinterface ITest{

publicvoid Test();

}

privateclass TestA implements ITest{

@Override

publicvoid Test() {

// TODO Auto-generated method stub

System.out.println("TestA");

}

}

privatestaticvoid TryGeneric1(List<? extends ITest> testList){

for(ITest tester:testList){

tester.Test();

}

}

privatestaticvoid TryGeneric2(List<?> testList){

// for(ITest tester:testList) // cause error

for(Object tester:testList){

((ITest)tester).Test();

}

}

privatestaticvoid TryGeneric3(List<ITest> testList){

for(ITest tester:testList){

((ITest)tester).Test();

}

}

privatestaticvoid TryGeneric4(List<Object> testList){

for(Object tester:testList){

((ITest)tester).Test();

}