function(T,R)

• R apply(T t) 根据类型T的参数获取类型R的结果
  • 使用场景例如，将String类型转化为Integer类型

public class Demo1Apply {
    public static Integer change(String s,Function<String, Integer> fun){
        return fun.apply(s);
    }

    public static void main(String[] args) {
        int a = change("123",(s)->Integer.parseInt(s));
        System.out.println(a);
    }
}

• andThen()用来进行组合操作

public class Demo2AndTen {
    //先把String转化为Integer，再把Integer转化为String
    public static String change(String s, Function<String, Integer> fun1,Function<Integer,String> fun2){
       return fun1.andThen(fun2).apply(s);
    }

    public static void main(String[] args) {
        String str = change("78",(s)->Integer.parseInt(s)+10,(number)->number.toString());
        System.out.println(str); //88
    }
}

• Practise

public class Practise {
    /*
    * 1.将字符串截取到年龄部分，得到字符串
    * 2.将上一步的字符串转化为int类型
    * 3.将上一步的数字累加100
    * */
    public static int change(String s, Function<String, String> fun1,Function<String,Integer> fun2,Function<Integer, Integer> fun3){
        return fun1.andThen(fun2).andThen(fun3).apply(s);
    }
    public static void main(String[] args) {
        int number = change("你好,20",s->s.split(",")[1],s->Integer.parseInt(s),num->{
            for (int i = 1; i <=100 ; i++) {
                num+=i;
            }
            return num;
        });
        System.out.println(number);//5070
    }
}