Java函数式接口之Predicate

痛定思痛。 2021-11-22 09:32 321阅读 0赞

## 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<String> 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<String> pre1, Predicate<String> 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<String> filter(String[] arr, Predicate<String> pre1,Predicate<String> pre2){
            ArrayList<String> 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<String> 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<String> pre1, Predicate<String> 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);
        }
    }