第四次作业 重写equals方法

使用上几次用到得User实体类，在其中重写equals方法。

    @Override
    public boolean equals(Object obj) {
        if(obj==null)return false;
        if(this==obj)return true;
        if(obj instanceof User) {
            User u = (User) obj;
            return this.getId()==u.getId()
                    &&this.getUsername().equals(u.getUsername())
                    &&this.getPassword().equals(u.getPassword())
                    &&this.getAge()==u.getAge();
        }
        return false;
    }

 这里重写的方法，将内容相同的User对象视为同一个User对象

测试方法

User类

public class User {
    private Integer id;
    private String username;
    private String password;
    private Integer age;
    public User() {
        super();
    }
    public User(Integer id, String username, String password, Integer age) {
        super();
        this.id = id;
        this.username = username;
        this.password = password;
        this.age = age;
    }
    
    
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    

    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", password=" + password + ", age=" + age + "]";
    }
    
    @Override
    public boolean equals(Object obj) {
        if(obj==null)return false;
        if(this==obj)return true;
        if(obj instanceof User) {
            User u = (User) obj;
            return this.getId()==u.getId()
                    &&this.getUsername().equals(u.getUsername())
                    &&this.getPassword().equals(u.getPassword())
                    &&this.getAge()==u.getAge();
        }
        return false;
    }
}

测试类EqualsTest.java

public class EqualsTest {
    public static void main(String[] args) {
        User u1 = new User(1, "三哥无邪", "1514010311", 21);
        User u2 = new User(1, "三哥无邪", "1514010311", 21);
        User u3 = u2;
        User u4 = new User(2, "三哥无邪", "1514010311", 21);
        System.out.println(u1.equals(u2));
        System.out.println(u1.equals(u3));
        System.out.println(u2.equals(u3));
        System.out.println(u2.equals(u4));
    }
}

结果