1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 | 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 ); } } <span style= "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</span> |
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