Java基础篇(泛型<T>常见用法)

//单泛型
class Test1<T> {
T t;

public Test1(T t) {
this.t = t;
}

void sys() {
System.out.println("a= " + t);
}

}

// 多泛型
class Test2<M, R> {
M m2;
R r2;

public Test2(M m2, R r2) {
this.m2 = m2;
this.r2 = r2;
}

public void sys() {
System.out.println("姓名: " + m2 + "  年龄   " + r2);
}
}

// 泛型嵌套
class Info<A, B> {
private A name;
private B age;

public Info(A name, B age) {
this.name = name;
this.age = age;
}

public A getName() {
return name;
}

public B getAge() {
return age;
}

}

class List<L> {
public L item;

public List(L item) {
this.item = item;
}

public L getItem() {
return item;
}
}

public class Fan {
public static void main(String args[]) {
// 最基本的泛型
Test1<String> t1 = new Test1<String>("Hello");
t1.sys();

// int会报错，应该用Integer包装类
Test2<String, Integer> t2 = new Test2<String, Integer>("张三", 11);
t2.sys();

// 嵌套的泛型
Info<String, Integer> info = null;
List<Info<String, Integer>> list = null;
info = new Info<String, Integer>("李四", 12);
list = new List<Info<String, Integer>>(info);
System.out.println("姓名  " + list.getItem().getName());
System.out.println("年龄  " + list.getItem().getAge());

// 通过泛型方法返回泛型类
Test1<String> t11 = fun("World");
t11.sys();

}

// <T> 返回的泛型类的类型
// Test1<T>泛型类
// T para 泛型参数
// 三个泛型必须一致
public static <T> Test1<T> fun(T para) {
Test1<T> temp = new Test1<T>(para);
return temp;
}
}