两个List对象，指定属性，取差集、交集。

差集

	// 差集 (list1 - list2 = list1 中不同数据)
        List<Person> reduce1 = list1.stream().filter(
        		a -> !list2.stream().map(
                b -> b.getAge()   "&"   b.getName()).collect(Collectors.toList())
                .contains(a.getAge()   "&"   a.getName())).collect(Collectors.toList());

        reduce1.parallelStream().forEach(System.out :: println);

    System.out.println("=============================得到差集 reduce2 (list2 - list1)==================================");
        List<Person> reduce2 = list2.stream().filter(
        		a -> !list1.stream().map(
        		b -> b.getAge()   "&"   b.getName()).collect(Collectors.toList()).contains(a.getAge()   "&"   a.getName()))
                .collect(Collectors.toList());
        reduce2.parallelStream().forEach(System.out :: println);

交集

	 // List1与 List2的交集  
	 // 过滤list1 ,遍历集合list2   
	 // anyMatch(Predicate p) 传入一个断言型函数，对流中所有的元素进行判断，只要有一个满足条件返回true，不满足false。 
	 // 取出list2中,符合判断条件的元素，返回值为true。将对象保存新集合中。
        List<Person> intersectA = list1.stream().filter(
                       a -> list2.stream().map(
                       Person::getName).anyMatch(   // 流中是否有元素能匹配给定的谓词，有则返回true 否false。
                       name -> Objects.equals(a.getName(), name)))
                       .collect(Collectors.toList());               
        // 遍历List
        intersectA.parallelStream().forEach(System.out :: println);

过滤

 // List对象数据去重
        Map<Object, Boolean> map = new HashMap<>();
        List<Person> list8 = list1.stream()
        		.filter(i -> map.putIfAbsent(i.getName() "&" i.getAge(), Boolean.TRUE) == null).collect(Collectors.toList());

实体类

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@AllArgsConstructor
@NoArgsConstructor
@Data
public class Person {

    private  String  name;

    private  Integer  age;

    private  Integer  weight;
    
}

测试类

@RunWith(SpringRunner.class)
@SpringBootTest
@ContextConfiguration(classes = bb.class)
public class test {

    @Test
    public void testSelectUser(){
        // list 1
        Person p1 = new Person("张三",null,50);  // a
        Person p2 = new Person("张三",26,60);    // a
        Person p3 = new Person("李四",null,70);  // a
        Person p4 = new Person("李四",110,60);  // a
        Person p5 = new Person(null,null,60);  // a
        Person p6 = new Person(null,null,70);  // a


        Person p11 = new Person("张三",25,50);
        Person p12 = new Person("张三",25,80);
        Person p13 = new Person("李5",110,60);
        Person p14 = new Person("李6",110,60);

        // List 2
        Person p21 = new Person("李四",null,22); // b
        Person p22 = new Person("李四",110,11);  // b
        Person p23 = new Person("张三",26,11);   // b
        Person p24 = new Person("张三",null,11); // b
        Person p25 = new Person(null,null,80);  // b

        Person p31 = new Person("张三",20,5);
        Person p32 = new Person("李四",119,11);

        List<Person> list1 = new ArrayList<>();
        list1.add(p1);
        list1.add(p2);
        list1.add(p3);
        list1.add(p4);
        list1.add(p5);
        list1.add(p6);
        list1.add(p11);
        list1.add(p12);
        list1.add(p13);
        list1.add(p14);

        List<Person> list2 = new ArrayList<>();
        list2.add(p21);
        list2.add(p22);
        list2.add(p23);
        list2.add(p24);
        list2.add(p25);
        list2.add(p31);
        list2.add(p32);
        list2.add(p5);
      }
    }

打印效果

************************************得到差集 reduce1 (list1 - list2 = list1)***********************************
Person{name='李5', age=110, weight=60}
Person{name='李6', age=110, weight=60}
Person{name='张三', age=25, weight=50}
Person{name='张三', age=25, weight=80}


=============================得到差集 reduce2 (list2 - list1)==================================
Person{name='李四', age=119, weight=11}
Person{name='张三', age=20, weight=5}


=============================得到交集==================================
Person{name='null', age=null, weight=70}
Person{name='null', age=null, weight=60}
Person{name='张三', age=null, weight=50}
Person{name='张三', age=25, weight=80}
Person{name='张三', age=25, weight=50}
Person{name='李四', age=null, weight=70}
Person{name='张三', age=26, weight=60}
Person{name='李四', age=110, weight=60}
=======================================================================

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