package com.it.pojo;?
import java.util.Comparator;
import java.util.Objects;
?
@Data
@NoArgsConstructor
@ToString
public class Person {
? ? private String name;
? ? private Integer age;
}

 
package com.it.test;
import java.util.ArrayList; 
import java.util.List;
import com.it.pojo.Person;  
import java.util.Comparator;
import java.util.stream.Collectors;
 
public class StreamTest {
    public static void main(String[] args) {
        Person person1 = new Person();
        person1.setAge(21);
        person1.setName("21");
 
        Person person2 = new Person();
        person2.setAge(19);
        person2.setName("19");
 
        Person person3 = new Person();
        person3.setAge(19);
        person3.setName("20");
 
        Person person4 = new Person();
        person4.setAge(20);
        person4.setName("20");
 
        Person person5 = new Person();
        person5.setAge(19);
        person5.setName("18");
        
        List<Person> people = new ArrayList<>();
        people.add(person1);
        people.add(person2);
        people.add(person3);
        people.add(person4);
        people.add(person5);
 
        List<Person> collect1 = people.stream().filter((person) -> {
            return person.getName().equals("18");  //取姓名是18的Person數(shù)據(jù)
        }).collect(Collectors.toList());
        System.out.println(collect1);
        
    
         List<Person> collect2 = people.stream().filter((person) -> {
            return person.getAge().intValue()==19 && person.getName().equals("19");  
        }).collect(Collectors.toList());
        System.out.println(collect2);
 
 
          List<Person> collect = people.stream().filter(person ->
            person.getName().equals("181")   //測試不滿足條件的list集合會是什么樣的
        ).collect(Collectors.toList()); 
 
        System.out.println(collect);    //集合size==0
        if(collect.size()==0){
            System.out.println("nihao");
        }
   }
}