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 ); } } 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
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import java.util.*;
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class Fruit { public String toString() { return "Fruit"; } }
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class Apple extends Fruit { public String toString(){ return "Apple"; } }
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class Person { public String toString(){ return "Person"; } }
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class ClassName<T> {//主类,把你文件名改成ClassName.java
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void show_1(T t){
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System.out.println("show_1 "+ t.toString());
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}
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<E> void show_2(E e){
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System.out.println("show_2 "+e.toString());
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}
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<T> void show_3(T t){
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System.out.println("show_3 "+t.toString());
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}
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public static void main(String[] args) {
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ClassName<Fruit> o = new ClassName<Fruit>();
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Fruit f = new Fruit();
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Apple a = new Apple();
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Person p = new Person();
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System.out.println("show_1 演示________________________");
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o.show_1( f );
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o.show_1( a );
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// 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
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// ClassName<Fruit>中已经限定了全局的T为Fruit,所以不能再加入Person;
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System.out.println("show_2 演示________________________");
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o.show_2( f );
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o.show_2( a );
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o.show_2( p );
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System.out.println("show_3 演示________________________");
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o.show_3( f );
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o.show_3( a );
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o.show_3( p );
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}
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}
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程序输出:
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show_1 演示________________________
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show_1 Fruit
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show_1 Apple
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show_2 演示________________________
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show_2 Fruit
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show_2 Apple
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show_2 Person
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show_3 演示________________________
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show_3 Fruit
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show_3 Apple
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show_3 Person