Java函数式接口之Predicate

概述

• predicate 接口是用来判断的
• test 方法用来判断，真则true，假则false

案例（一）

import java.util.function.Predicate;
public class PredicateInterface_lianxi {
    public static boolean checkString(String s, Predicate pre){
        return pre.test(s);
    }
    public static void main(String[] args) {
        String name = "abcded";
        boolean a = checkString(name,(s)->{
            if (name.length() > 5){
                return false;
            }else{
                return true;
            }
        });
        //对其进行优化
        boolean b = checkString(name,s->s.length()>5);
        System.out.println(a+""+b);
    }
}

• Predicate 中的方法and

案例（二）

import java.util.function.Predicate;
public class PredicateAnd_lianxi {
    public static  boolean checkTrue(String s, Predicate pre1, Predicate pre2){
//        return pre1.test(s) && pre2.test(s);
        return pre1.and(pre2).test(s);
    }
    public static void main(String[] args) {
        String str = "abcdefg";
        boolean b = checkTrue(str,(s)->{
            return str.length()>5;
        },(s)->{
            return str.contains("a");
        });
        System.out.println(b);
        //对其进一步优化
        boolean c = checkTrue(str,s-> str.length()>5,s-> str.contains("a"));
        System.out.println(c);
    }
}

案例（三）

import java.util.ArrayList;
import java.util.function.Predicate;
public class Predicate_informationshaixuan {
    public static ArrayList filter(String[] arr, Predicate pre1,Predicate pre2){
        ArrayList list = new ArrayList<>();
        for (String s : arr) {
            boolean b =pre1.and(pre2).test(s);
            if (b){
                list.add(s);
            }
        }
        return list;
    }
    public static void main(String[] args) {
        String[] arr = {"哈哈哈哈，女","呵呵呵呵，女","嘿嘿嘿嘿，男","哦哦哦，女"};
        ArrayList aa = filter(arr,(s)->{
            return s.split("，")[1].equals("女");
        },(s)->{
            return s.split("，")[0].length()==4;
        });
        for (String s : aa) {
            System.out.println(s);
        }
    }
}

Predicate 中的方法or

 import java.util.function.Predicate;
public class PredicateOr_lianxi {
    public static  boolean checkTrue(String s, Predicate pre1, Predicate pre2){
        return pre1.or(pre2).test(s);
    }
    public static void main(String[] args) {
        String str = "abcdefg";
        boolean b = checkTrue(str,(s)->{
            return str.length()>5;
        },(s)->{
            return str.contains("h");
        });
        System.out.println(b);
        //对其进一步优化
        boolean c = checkTrue(str,s->str.length()>5,s->str.contains("h"));
        System.out.println(c);
    }
}