java 泛型综合例子

除了用到了泛型，还用到了<T extends Info>来设定上限。看实例：

interface Info{//只有此接口的子类才能表示人的信息
}
class Person<T extends Info>{           //为参数T设置一个上限，必须是Info或Info的子类。
	private T info;
    /*
		构造函数
	*/
	public Person(T info){
		this.info=info;
	}
	public void setInfo(T info){
		this.info=info;
	}
	public T getInfo(){
		return this.info;
	}
	public String toString(T info){
		return this.info.toString();
	}
}

class Contact implements Info{           //表明Contact是Info的子类，他可以使用在Person中
	private String address;
	private String telphone;
	private String zipcode;
	/*
		构造函数
	*/
	public Contact(String address,String telphone,String zipcode){
		this.address=address;
		this.telphone=telphone;
		this.zipcode=zipcode;
	}
	public void setAddress(String address){
		this.address=address;
	}
	public String getAddress(){
		return this.address;
	}
	public void setTelphone(String telphone){
		this.telphone=telphone;
	}
	public String getTelphone(){
		return this.telphone;
	}
	public void setZipcode(String zipcode){
		this.zipcode=zipcode;
	}
	public String getZipcode(){
		return this.zipcode;	
	}
	public String toString(){
		return "联系方式：" + "\n" +
				"\t|- 联系电话：" + this.telphone + "\n" + 
				"\t|- 联系地址：" + this.address + "\n" + 
				"\t|- 邮政编码：" + this.zipcode ;
	}
}

class Introduction implements Info{
	private String name;
	private String sex;
	private int age;
	/*
		构造函数
	*/
	public Introduction(String name,String sex,int age){
		this.name=name;
		this.sex=sex;
		this.age=age;
	}
	public void setName(String name){
		this.name=name;
	}
	public String getName(){
		return this.name;
	}
	public void setSex(String sex){
		this.sex=sex;
	}
	public String getSex(){
		return this.sex;
	}
	public void setAge(int age){
		this.age=age;
	}
	public int getAge(){
		return this.age;
	}
	public String toString(){
		return "基本信息：" + "\n" +
				"\t|- 姓名：" + this.name + "\n" + 
				"\t|- 性别：" + this.sex + "\n" + 
				"\t|- 年龄：" + this.age ;
	}
}

public class ExampleFanxing{
	public static void main(String[] args){
		Person<Contact> p=null;
		Person<Introduction> p1=null;
		Contact c = new Contact("110","北三环东路","100029");
		Introduction i= new Introduction("武开英","男",22);
		p = new Person<Contact>(c);
		p1=new Person<Introduction>(i);
		System.out.print(p.getInfo().toString());
		System.out.print(p1.getInfo().toString());
		
	}
}

class Person<T extends Info>{}表明了Person类的上限，只能是Info或Info的子类。类Contact和Introduction继承了接口Info，满足条件。

如果去掉Contact类中的implements Info会出现如下错误：

E:\JAVA\NotePadJava\Demo1>javac ExampleFanxing.java
ExampleFanxing.java:100: 错误: 类型参数Contact不在类型变量T的范围内
                Person<Contact> p=null;
                       ^
  其中, T是类型变量:
    T扩展已在类 Person中声明的Info
ExampleFanxing.java:104: 错误: 类型参数Contact不在类型变量T的范围内
                p = new Person<Contact>(c);
                               ^
  其中, T是类型变量:
    T扩展已在类 Person中声明的Info
2 个错误