为什么这个 If 语句不能正确地将存储的变量与数组中的元素进行比较？

Question

所以我只是在学习java时做一些基本测试，我很好奇为什么这不起作用：

public static void main(String[] args) {
        String[] names={"John","Mark","Suzy","Anthony"};
        String[] passwords={"passw0rd","CandyC4ne","x5021","ADawg55"};
        System.out.println("Please indicate which user you would like to log in as:\n(1)John\n(2)Mark\n(3)Suzy\n(4)Anthony");
        Scanner x=new Scanner(System.in);
        int y=x.nextInt()-1;
        System.out.print("Please enter the password to log into "+names[y]+"'s account: ");
        Scanner a=new Scanner(System.in);
        String newpass=a.nextLine();
        System.out.println(passwords[y]);
        if(passwords[y]==newpass){
            System.out.print("Hello "+names[y]+"!");
        }else{
            System.out.println("Incorrect Password. "+passwords[y]+" "+newpass);
        }
    }

passwords[y]和newpass都是完全相同的字符串，当我尝试时：

if(passwords [y]=="passw0rd");

（显然选择“John”）它确实有效，所以我希望有人可以解释其中的差异以及如何解决它，以便更好地接受用户输入。

另外，我将采用 for 循环作为答案，但我希望我可以避免它。

Answer 1

切勿使用 == 来比较字符串。始终使用 equals 或 equalsIgnoreCase 方法。 == 将检查指向同一对象的两个引用，而 equals 将检查字符串的内容。

Answer 2

使用 等于< /a> 或 compareTo 方法来比较两个字符串，而不是比较引用的 == 。

import java.util.*;

public class Password{
    public static void main(String[] args) {
        String[] names={"John","Mark","Suzy","Anthony"};
        String[] passwords={"passw0rd","CandyC4ne","x5021","ADawg55"};
        System.out.println("Please indicate which user you would like to log in as:\n(1)John\n(2)Mark\n(3)Suzy\n(4)Anthony");
        Scanner x=new Scanner(System.in);
        int y=x.nextInt()-1;
        System.out.print("Please enter the password to log into "+names[y]+"'s account: ");
        Scanner a=new Scanner(System.in);
        String newpass=a.nextLine();
        System.out.println(passwords[y]);
        if(passwords[y].equals(newpass)){
            System.out.print("Hello "+names[y]+"!");
        }else{
            System.out.println("Incorrect Password. "+passwords[y]+" "+newpass);
        }
    }
}

输出：

$ javac Password.java && java Password 
Please indicate which user you would like to log in as:
(1)John
(2)Mark
(3)Suzy
(4)Anthony
1
Please enter the password to log into John's account: passw0rd
passw0rd
Hello John!