Java基础篇(泛型<T>常见用法)

清疚 2022-07-30 14:29 145阅读 0赞

//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;
        }
    }

运行结果如下  
![这里写图片描述][20160419073954827]

[20160419073954827]: /images/20220724/c5ae9859254b40b89318cf28eecc1243.png