list 判断对象属性是否存在，重写equals()方法

实体类User

import java.util.Objects;

public class User {
    private String userName;
    private String userCode;

    public User() {
	}

	public User(String userName, String userCode) {
		this.userName = userName;
		this.userCode = userCode;
	}

	public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserCode() {
        return userCode;
    }

    public void setUserCode(String userCode) {
        this.userCode = userCode;
    }
    
    @Override
    public boolean equals(Object obj){
    	if(obj instanceof User){
    		User user = (User)obj;
    		return this.userName.equals(user.getUserName()) && this.userCode.equals(user.getUserCode());
    	}
    	return super.equals(obj);
    }
    
    @Override
    public int hashCode(){
    	return Objects.hash(this.userName, this.userCode);
    }
}

测试类

import java.util.ArrayList;
import java.util.List;

public class Test {
	
    public static void main(String[] args) throws Exception {
    	List<User> userList = new ArrayList<User>();
    	User u1 = new User("name1","code1");
    	User u2 = new User("name2","code2");
    	userList.add(u1);
    	userList.add(u2);
    	
    	//name、code都相同返回true
    	User u3 = new User("name2","code2");
    	System.out.println(userList.contains(u3));
    	
		//返回false
    	User u4 = new User("name1","code2");
    	System.out.println(userList.contains(u4));
	}

}