Question

所以我尝试在我的程序中进行密码检查，目标是，如果用户输入正确的密码，程序将回复：＆＃34;你通过＆＃34;，如果不是＆＃34;你＆＃39;错了＆＃34;。问题是Eclipse告诉我＆＃34; Fish（这是密码）无法解析为变量＆＃34;

import java.util.Scanner;

public class Password {

    public static void main(String args[]) {
        Scanner scan = new Scanner(System.in);
        String password;

        password = Fish;

        System.out.println("What is the password? ");
        scan.nextLine();

        if (scan.equals(password)) {
            System.out.println("You pass!");
        }
        else {
            System.out.println("You're wrong!");
        }
    }
}

我尝试以Eclipse的方式解决问题，但是在我运行程序后输入错误的密码时，我得到了错误的密码：

import java.util.Scanner;

public class Password {

    private static final String Fish = null;

    public static void main(String args[]) {
        Scanner scan = new Scanner(System.in);
        String password;

        password = Fish;

        System.out.println("What is the password? ");
        scan.nextLine();

        if (scan.equals(password)) {
            System.out.println("You pass!");
        }
        else {
            System.out.println("You're wrong!");
        }
    }
}

我尝试在线查看，我实际上正在阅读Java Programming for Dummies，但仍然没有运气，希望你可以帮助我，我很感激！

谢谢！

Answer 1

你已经为它编写了一些错误的语法。试试这段代码。我添加了必要的注释，让你理解我在下面的代码中做了什么。

public static void main(String args[]) {
Scanner scan = new Scanner(System.in);
String password;

 password = "Fish";  // assigning  value to String password

 System.out.println("enter value");

String temp=scan.nextLine(); //scanner takes nextline entered and assign it to temp

   //  if (scan.equals(password))  is wrong ,you want to compare value taken by scanner , what you have wriiten is incorrect. scan is object of Scanner.Not value taken by it


 if(temp.equals(password))  //if entered value eqauls your assigned       password value
  {
      System.out.println("You pass!"); // else print you pass
  }
else
{
  System.out.println("You're wrong!"); //else  print "you are wrong"
}

Answer 2

if (isValid(password)) 
{  
    System.out.println("You pass!");  
} 
else 
{  
    System.out.println("You're wrong!");  
}

Answer 3

首先，你永远不会在变量中读取你的输入！然后你试图检查＆＃34;扫描＆＃34;之间的平等。 Scanner.Instead读取输入＆＃34; scan.nextLine（）;＆＃34;在一个变量中说＆＃34; var＆＃34;然后调用var.equals（密码）。还要检查你的String＆＃34; Fish＆＃34;最初是null，它会给你一个NullPointerException！

Answer 4

欢迎来到Java World！

在你的程序中，你通过在Scanner对象上调用equals来犯一个小错误。还记得在完成后关闭可用的扫描程序资源。

请参阅以下代码。

import java.util.Scanner;

public class Password {

private static final String Fish = "Fish";

public static void main(String args[]) {
    Scanner scan = new Scanner(System.in);

    System.out.println("What is the password? ");

    if (scan.nextLine().equals(Fish)) {
        System.out.println("You pass!");
    }
    else {
        System.out.println("You're wrong!");
    }

}

}

试着写一个涉及密码的简单程序（java）

4 个答案: