Java泛型小记

Automobile类：

public class Automobile {
private String name;
public Automobile(String name){
this.name= name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}

Holder1类：持有指定的单一类型对象。

public class Holder1 {
private Automobile automobile;
public Holder1(Automobile automobile){
this.automobile = automobile;
}
public Automobile get(){
return this.automobile;
}
}

Holder2类：持有Object对象。

public class Holder2 {
private Object object;
public Holder2(Object object){
this.setObject(object);
}
public Object getObject() {
return object;
}
public void setObject(Object object) {
this.object = object;
}
}

Holder3类：使用泛型，持有单一对象，但是暂时不指定其类型，到使用时决定持有何种对象。

public class Holder3 <T>{
private T t;
public Holder3(T t){
this.setT(t);
}
public T getT() {
return t;
}
public void setT(T t) {
this.t = t;
}
}

主程序Main：

public class Main {
public static void main(String[] args) {
/*使用Holder1*/
Holder1 holder1 = new Holder1(new Automobile("Iphone"));
System.out.println(holder1.get().getName());

/*使用Holder2*/
//使holder2持有String类型对象
Holder2 holder2 = new Holder2("XiaoMi");
System.out.println(holder2.getObject());
//更改holder2中持有的对象类型
holder2.setObject(new Automobile("HuaWei"));
//向下转型Object->Automobile
Automobile automobile = (Automobile) holder2.getObject();
System.out.println(automobile.getName());

/*使用Holder3*/
//告诉编译器holder3持有的对象类型为String
//此时holder3拥有的对象类型只能为String，不能变更
Holder3<String> holder3 = new Holder3<String>("Vivo");
System.out.println(holder3.getT());
//告诉编译器anotherHolder3持有的对象类型为Automobile
//此时anotherHolder3拥有的对象类型只能为Automobile，不能变更
Holder3<Automobile> anotherHolder3 = new Holder3<Automobile>(new Automobile("Oneplus"));
System.out.println(anotherHolder3.getT().getName());
}
}

程序运行结果为：

Iphone
XiaoMi
HuaWei
Vivo
Oneplus