JAVA扫描器在if/else语句中输入字符串

Question

这个问题已经有答案了:

How do I compare strings in Java? (23 个回答)

已关闭 9 年前。

您好，我正在编写一个简单的用户名/密码输入，但我的代码绕过所有 if/if else 语句并转到 else 语句。我不确定我的语法是否不正确或者使用 if/else 语句是否不正确。或者如果我只是编码错误。请帮忙!

import java.util.Scanner;

public class Passwords
{
    public static void main (String[] args)
    {
        Scanner input = new Scanner(System.in);
        String[] username = {"admin1", "admin2", "admin3", "admin4", "admin5"};
        String[] password = {"pass1", "pass2", "pass3", "pass4", "pass5"};
        System.out.println("Please enter in one of the following usernames : admin1, admin2, admin3, admin4, or admin5");
        String userinput = input.nextLine();
        System.out.println("Please enter in the password corresponding to your username: pass1, pass2, pass3, pass4, or pass5");
        String passinput = input.nextLine();
        if (userinput == username[0] && passinput == password[0])
        {
            System.out.println("Access granted!");
        }
        else if (userinput == username[1] && passinput == password[1])
        {
            System.out.println("Access granted!");
        }
        else if (userinput == username[2] && passinput == password[2])
        {
            System.out.println("Access granted!");
        }
        else if (userinput == username[3] && passinput == password[3])
        {
            System.out.println("Access granted!");
        }
        else if (userinput == username[4] && passinput == password[4])
        {
            System.out.println("Access granted!");
        }
            else 
            {
                System.out.println("Sorry the username or password you entered is incorrect. Please try again");
                System.out.println("Please enter in one of the following usernames : admin1, admin2, admin3, admin4, or admin5");
                String userinput1 = input.next();
                System.out.println("Please enter in the password corresponding to your username: pass1, pass2, pass3, pass4, or pass5");
                String passinput1 = input.next();
                if (userinput1 == username[0] && passinput1 == password[0])
                {
                    System.out.println("Access granted!");
                }
                else if (userinput1 == username[1] && passinput1 == password[1])
                {
                    System.out.println("Access granted!");
                }
                else if (userinput1 == username[2] && passinput1 == password[2])
                {
                    System.out.println("Access granted!");
                }
                else if (userinput1 == username[3] && passinput1 == password[3])
                {
                    System.out.println("Access granted!");
                }   
                else if (userinput1 == username[4] && passinput1 == password[4])
                {
                    System.out.println("Access granted!");
                }
                else 
                {
                    System.out.println("Sorry, your username/password does not match our database. Contact the administrator.");
                }
            }
        }
}

Answer 1

use, userinput.equals(username[0])//这将比较字符串值

在 java 中 == 将比较对象 ID，如果它们是不同的对象，则始终为 false。