一、泛型类及特点

1.1泛型的类型参数可以是泛型类
class Cls1{

T a;
public Cls1(T a){
    this.a = a;
}
public T getData(){
    return a;
}

}

public class Test {

public static void main(String[] args) {        
    Cls1<Cls1<Integer>> cls1 = new Cls1<Cls1<Integer>>(new Cls1<Integer>(10));
    System.out.println(cls1.getData().getData());
}

}
/*
10
*/

1.2泛型类可以同时设置多个类型参数
class Cls4<T,T2>{

T a;
T2 b;
public Cls4(T a,T2 b){
    this.a = a;
    this.b = b;
}
public T getData3(){
    return a;
}
public T2 getData4(){
    return b;
}

}

public class Test {

public static void main(String[] args) {        
    Cls4<Integer,String> c4 = new Cls4<Integer,String>(100,"wei");
    System.out.println(c4.getData3());
    System.out.println(c4.getData4());
    System.out.println(c4.getData3() + c4.getData4()); //+表示连接起来，并不是相加
    
    Cls4<Integer,Integer> c5 = new Cls4<Integer,Integer>(100,10);
    System.out.println(c5.getData3());
    System.out.println(c5.getData4());
    System.out.println(c5.getData3() + c5.getData4());
    int n = 0;
    n = c5.getData3() + c5.getData4();    //泛型在旧版本不可以相加，现在可以相加
    System.out.println("n=" + n);
}

}
/*
100
wei
100wei
100
10
110
n=110
*/

1.3泛型类可以继承泛型类
abstract class Cls1{

T a;
public Cls1(T a){
    this.a = a;
}
public T getData(){
    return a;
}
abstract void printInfo();    //抽象方法

}

class Cls2<T,T2> extends Cls1{ //继承Cls1

T2 b;
public Cls2(T a,T2 b){
    super(a);
    this.b = b;
}
public T2 getData2(){
    return b;
}
@Override
//可以把这个注释掉，在类前面继续加abstract，不需要实现这个方法
void printInfo() {
    // TODO Auto-generated method stub
    System.out.println("输出");
}

}

public class Test {

public static void main(String[] args) {        
    Cls2<Integer,String> cls = new Cls2<Integer,String>(10,"xiao");
    cls.printInfo();
    System.out.println(cls.getData());
    System.out.println(cls.getData2());
}

}
/*
输出
10
xiao
*/

1.4泛型类可以实现泛型接口

abstract class Cls1{

T a;
public Cls1(T a){
    this.a = a;
}
public T getData(){
    return a;
}
abstract void printInfo();    //抽象方法

}

//接口
interface Cls3{

abstract void printInfoInCls3(T t);

}

class Cls2<T,T2,T3> extends Cls1 implements Cls3{ //继承Cls1，接口Cl3，添加一个T3

T2 b;
public Cls2(T a,T2 b){
    super(a);
    this.b = b;
}
public T2 getData2(){
    return b;
}
@Override
//可以把这个注释掉，在类前面继续加abstract，不需要实现这个方法
void printInfo() {
    // TODO Auto-generated method stub
    System.out.println("输出");
}
//接口实现
public void printInfoInCls3(T3 t) {
    // TODO Auto-generated method stub
    System.out.println(t);
}

}

public class Test {

public static void main(String[] args) {        
    Cls2<Integer,String,String> cls = new Cls2<Integer,String,String>(10,"xiao");
    cls.printInfo();
    System.out.println(cls.getData());
    System.out.println(cls.getData2());
    
    cls.printInfoInCls3("小伟");
}

}
/*
输出
10
xiao
小伟
*/