list contains比较对象需要注意的地方

骑猪看日落 2022-05-15 18:14 165阅读 0赞

List contains()比较对象，需要重写对象的equals()和hashCode()方法。

package com.kanzhun.phoenix.admin.mytest;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Objects;
    
    /**
     * ContainsTest
     *
     * @author jibingbing
     * @date 2018/10/30
     **/
    public class ContainsTest {
    
        public static void main(String[] args) {
            Student student1 = new Student(1, "ji", 100);
            Student student2 = new Student(2, "ji", 100);
            Student student3 = new Student(1, "ji1", 100);
    
            List<Student> students = new ArrayList<>();
            students.add(student1);
    //        students.add(student2);
            students.add(student3);
    
            System.out.println(students.contains(student2));
        }
    
        static class Student {
            int id;
            String name;
            int score;
    
            public Student(int id, String name, int score) {
                this.id = id;
                this.name = name;
                this.score = score;
            }
    
            public int getId() {
                return id;
            }
    
            public void setId(int id) {
                this.id = id;
            }
    
            public String getName() {
                return name;
            }
    
            public void setName(String name) {
                this.name = name;
            }
    
            public int getScore() {
                return score;
            }
    
            public void setScore(int score) {
                this.score = score;
            }
    
            @Override
            public boolean equals(Object o) {
                if (this == o) return true;
                if (o == null || getClass() != o.getClass()) return false;
                Student student = (Student) o;
                return score == student.score &&
                        Objects.equals(name, student.name);
            }
    
            @Override
            public int hashCode() {
                return Objects.hash(name, score);
            }
        }
    }