5. Lambda Predicate

1.源码：

@FunctionalInterface
public interface Predicate {
    
    boolean test(T t);
    
    default Predicate and(Predicate other) {
        Objects.requireNonNull(other);
        return (t) -> test(t) && other.test(t);
    }
    
    default Predicate negate() {
        return (t) -> !test(t);
    }
    
    default Predicate or(Predicate other) {
        Objects.requireNonNull(other);
        return (t) -> test(t) || other.test(t);
    }

    
    static  Predicate isEqual(Object targetRef) {
        return (null == targetRef)
                ? Objects::isNull
                : object -> targetRef.equals(object);
    }
}

简单案例:

public static void main(String[] args) {
        
        //设置一个大于7的过滤条件
        Predicate predicate = x -> x > 7;
        System.out.println(predicate.test(10)); //输出 true
        System.out.println(predicate.test(6));  //输出 fasle
         
        //在上面大于7的条件下，添加是偶数的条件
        predicate = predicate.and(x -> x % 2 == 0);
        System.out.println(predicate.test(6));  //输出 fasle
        System.out.println(predicate.test(12)); //输出 true
        System.out.println(predicate.test(13)); //输出 fasle
        
        predicate = x -> x > 5 && x < 9;
        System.out.println(predicate.test(10)); //输出 false
        System.out.println(predicate.test(6));  //输出 true
    }

案例代码：

实体：

package com.study.stream;

import java.util.Objects;

public class Person implements Comparable{
    private String name;
    private Integer age;
    private Integer height;

    public Person(String name, Integer age, Integer height) {
        this.name = name;
        this.age = age;
        this.height = height;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Integer getHeight() {
        return height;
    }

    public void setHeight(Integer height) {
        this.height = height;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Person person = (Person) o;
        return name.equals(person.name) &&
                age.equals(person.age);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, age);
    }

    @Override
    public String toString() {
        return String.format("姓名:%s;年龄:%s;身高:%s;",this.name,this.age,this.height);
    }
    
    @Override
    public int compareTo(Person o) {
        return this.getAge().compareTo(o.getAge());
    }
}

案例：

package com.study.stream;

import java.util.function.Predicate;

public class PredicateDomel {

    public static void main(String[] agr){
        Predicate predicate= x -> x>2;

        System.out.println("***********-- predicate test 判断是否符合--************");
        System.out.println(predicate.test(1));

        Predicate predicate1= x -> x<10;
        System.out.println("***********-- predicate and 两个--************");
        System.out.println(predicate.and(predicate1).test(6));

        System.out.println(predicate.and(predicate1).test(40));

        System.out.println("***********-- predicate or 或--************");
        System.out.println(predicate.or(predicate1).test(40));

        System.out.println("***********-- predicate negate 相反--************");
        System.out.println(predicate.negate().test(4));

        System.out.println("***********-- predicate isEqual 比较相等--************");
        Person person= new Person("张一",18,172);
        Person person1=   new Person("张一",18,175);
        System.out.println(Predicate.isEqual(person).test(person1));

    }
}