使用字符串退出 do while 循环答案

【问题标题】：exiting a do while loop using a string使用字符串退出 do while 循环
【发布时间】：2012-10-06 22:35:43
【问题描述】：

好的。

这是我的问题。我在做骰子游戏时遇到了一些困难。我遇到的问题是使用 do while 循环使其退出。这是我的代码。我将在

中进一步解释我的意思

import java.util.Scanner;

public class Dice
{
 public static void main (String[] args)
 {
    int diceGuess;
    int rollNum, roll1, roll2, roll3;
    String playAgain = "yes";

    Scanner sc = new Scanner(System.in);


     // Create two separate dice objects to create a pair of dice
            Roll die1 = new Roll();
            Roll die2 = new Roll();

    // get from the user the number of dice rolls
            System.out.print ("Please enter a number between 2 and 12 to begin: ");
            diceGuess = sc.nextInt();

    do
    {       
        // loop to show rolls
        for (rollNum = 1; rollNum <=3; rollNum++)
          {
          System.out.println("**********Roll #: " + rollNum + " ************");
            roll1 = die1.roll();
            roll2 = die2.roll();

                //if statement to display you win if you win, and to make the loop break.
                if(diceGuess==roll1+roll2)  
                    {
                        System.out.println("You win!");
                        rollNum = 4;
                    }

                if(rollNum == 3)
                    {
                        System.out.println("You lose.\n");
                        System.out.println("Would you like to play again?");
                        playAgain = sc.nextLine();
                        rollNum ++;
                    }
            }           
        }while(playAgain == "yes");

}

}

这是我的实用程序类。我希望它询问用户是否要再次播放，然后如果用户输入否，我希望它退出。我确信这只是我的一个小误解。
非常感谢stackoverflow。

这是另一个类

//Justin Le
//Dice class


import java.util.Random;

public class Roll
{
//variables used in class
private Random randomRoll = new Random();
private int roll;
boolean playAgain = false;


//constructor
public Roll()
{
    roll = 0;
}

//method named roll to return roll number and inside, calls a method to display the roll.
public int roll()
{
    roll = randomRoll.nextInt(6) + 1;
    showRoll(roll);  //accesses showRoll to output in driver class.
    return roll;

}

public boolean test()
{
    playAgain = !playAgain;
    return playAgain;
}


//displays picture of dice roll
private void showRoll(int r)
    {
        switch(r)
            {
            case 1:
                System.out.println("One: \n" +
                                         " \n  "   +
                                         "  *  \n" +
                                         " \n  ");
            break;

            case 2:
                System.out.println("Two: \n" +
                                         "*    \n" +
                                         "     \n" +
                                         "    *\n");
            break;

            case 3:
                System.out.println("Three:\n" +
                                         "*    \n" +
                                         "  *  \n" +
                                     "    *\n");
            break;

            case 4:
                System.out.println("Four:\n" +
                                        "*   *\n" +
                                     "     \n" +
                                     "*   *\n");
            break;

            case 5:
                System.out.println("Five:\n" +
                                        "*   *\n" +
                                         "  *  \n" +
                                         "*   *\n");
            break;

            case 6:
                System.out.println("Six: \n" +
                                        "*   *\n" +
                                         "*   *\n" +
                                         "*   *\n");
            break;
            default:
                System.out.println("error\n");
    }

}

}

【问题讨论】：

你必须在对象上使用 .equals()，你可以在原始类型上使用 ==

标签： java loops do-while

【解决方案1】：

在你的时候，使用equals() 方法来比较字符串.. : -

playAgain.equals("yes")

请参阅this excellent post 了解使用equals() 和== 的比较差异。

在您的第一个代码中：-

if(rollNum == 3)
{
    System.out.println("You lose.\n");
    System.out.println("Would you like to play again?");
    //playAgain = sc.nextLine();

    // Change your nextLine() to next()
    playAgain = sc.next();
    rollNum ++;
}

【讨论】：

【解决方案2】：

改变

playAgain == "yes"

到

"yes".equals(playAgain)

【讨论】：

我这样做了，但我认为其中一个问题是......当它到达我输入是或否的地步时......它只是不断给我新的行来输入 no no no不不

【解决方案3】：

使用 while(plyaAgain.equals("yes"));

点击此链接了解字符串比较的详细信息： How do I compare strings in Java?

【讨论】：

【解决方案4】：

改变这个：

while(playAgain == "yes");

到这里：

while(playAgain.equals("yes"));

【讨论】：