创建一个嵌套的for循环

Question

因此，在尝试创建一个随机数生成器以提示用户不断猜测所生成的数字直到正确为止时，我遇到了一些问题。

一切正常，直到我尝试添加再次播放的选项。 问题是，如果他们猜错了数字，则无论他们猜得太高，太低还是输入无效，它都会不断重复发出相同的错误消息。 如果是第一次正确猜中该数字，则说明一切正常，并会提示再次播放并正常运行。

事实是，我使用了2个for循环，因为当它们开始猜测时，我不需要：

“此程序将生成一个0到100的随机数，您必须猜测。”

要在他们猜错答案时每次输出一次，我只希望在他们选择再次播放的选项时才输出，这就是我制作嵌套for循环的原因。 但是问题仍然在于，在第一个错误的猜测显示出相同的答案之后，内部的for循环会进入一个无尽的循环。

import javax.swing.JOptionPane;
import java.util.Random;
import javax.swing.UIManager;
import java.awt.*;

public class RandomNumberGuesser{
    public static void main(String[] args){
        UIManager m1=new UIManager();
        Color g = Color.gray;
        Color lg = g.brighter();
        m1.put("OptionPane.background", lg);
        m1.put("Panel.background", lg);

        int x;
        for(x = 1; true; x++){
        Random random = new Random();
        int randomNumber = random.nextInt(100);
        System.out.println(randomNumber);
        JOptionPane.showMessageDialog(null,
            "This program will generate a random number from 0 to 100 which you have to guess.",
            "Number Guesser",
            JOptionPane.INFORMATION_MESSAGE);
            String guess = JOptionPane.showInputDialog(null,
                "Guess a number.",
                "Guess",
                JOptionPane.QUESTION_MESSAGE);
                if(guess == null){
                    System.out.println("The user has terminated the program");
                    System.exit(0);
                    }
            int guess1 = Integer.parseInt(guess);

            int y;
            for(y = 1; true; y++){
                if(guess1 > 100 || guess1 < 0)
                JOptionPane.showMessageDialog(null,
                    "Guess is out of range!\nPlease enter valid input.",
                    "Invalid Input",
                    JOptionPane.WARNING_MESSAGE);

            else if(randomNumber > guess1)
                JOptionPane.showMessageDialog(null,
                    "You guessed too low.\nGuess again!",
                    "Your guess",
                    JOptionPane.INFORMATION_MESSAGE);

            else if(randomNumber < guess1)
                JOptionPane.showMessageDialog(null,
                    "You guessed too high.\nGuess again!",
                    "Your guess",
                    JOptionPane.INFORMATION_MESSAGE);

            else{
                JOptionPane.showMessageDialog(null,
                    "You guessed the number right!\nIt took you "+y+" attempt(s) to guess it.",
                    "Congratulations!",
                    JOptionPane.INFORMATION_MESSAGE);
                if (JOptionPane.showConfirmDialog(null, "Want to play again?", "Play again?",
                        JOptionPane.YES_NO_OPTION) == JOptionPane.NO_OPTION) {
                    System.out.println("Play again soon!");
                    System.exit(0);
                }
                else{
                    y = 0;
                    break;
                    }
                }
            }
        }
    }
}

Answer 1

使用while循环。

这是一个如何循环直到满足某些条件的示例（在这种情况下，如果数字介于1和100之间（包括1和100），则为：

Scanner keyboard = new Scanner(System.in);
    int number;
    boolean good = false;
    do
    {
      System.out.println("Enter a number between 1 and 100: ");
      number = keyboard.nextInt();
      if(number > 0 && number <= 100) {
        System.out.println("Good choice: \"" + number + "\"!");
        good = true;
      }
      else
        System.out.println("Invalid number: \"" + number + "\"! Please enter a number between 1 and 100!\n");
    }
    while (!good);
 } 

输入样例：

-1 -2 0 1

输出：

Enter a number between 1 and 100: 
Invalid number: "-1"! Please enter a number between 1 and 100!

Enter a number between 1 and 100: 
Invalid number: "-2"! Please enter a number between 1 and 100!

Enter a number between 1 and 100: 
Invalid number: "0"! Please enter a number between 1 and 100!

Enter a number between 1 and 100: 
Good choice: "1"!

Answer 2

您可以尝试以下方法：

public class RandomNumberGuesser {
public static void main(String[] args) {
    // UIManager m1=new UIManager();
    Color g = Color.gray;
    Color lg = g.brighter();
    UIManager.put("OptionPane.background", lg);
    UIManager.put("Panel.background", lg);

    Random random = new Random();
    int attempts = 0; // Number of attempts

    int randomNumber = random.nextInt(100);
    System.out.println(randomNumber);

    // This outside the loop so is showed just ONE time
    JOptionPane.showMessageDialog(null,
                    "This program will generate a random number from 0 to 100 which you have to guess.", "Number Guesser", JOptionPane.INFORMATION_MESSAGE);

    while (true) {

        attempts++;

        String guess = JOptionPane.showInputDialog(null, "Guess a number.",
                "Guess", JOptionPane.QUESTION_MESSAGE);
        if (guess == null) {
            System.out.println("The user has terminated the program");
            System.exit(0);
        }
        int guess1 = Integer.parseInt(guess);

            if (guess1 > 100 || guess1 < 0)
                JOptionPane
                        .showMessageDialog(
                                null,
                                "Guess is out of range!\nPlease enter valid input.",
                                "Invalid Input",
                                JOptionPane.WARNING_MESSAGE);

            else if (randomNumber > guess1)
                JOptionPane.showMessageDialog(null,
                        "You guessed too low.\nGuess again!", "Your guess",
                        JOptionPane.INFORMATION_MESSAGE);

            else if (randomNumber < guess1)
                JOptionPane.showMessageDialog(null,
                        "You guessed too high.\nGuess again!",
                        "Your guess", JOptionPane.INFORMATION_MESSAGE);

            else {
                JOptionPane
                        .showMessageDialog(null,
                                "You guessed the number right!\nIt took you "
                                        + attempts + " attempt(s) to guess it.",
                                "Congratulations!",
                                JOptionPane.INFORMATION_MESSAGE);
                if (JOptionPane.showConfirmDialog(null,
                        "Want to play again?", "Play again?",
                        JOptionPane.YES_NO_OPTION) == JOptionPane.NO_OPTION) {
                    System.out.println("Play again soon!");
                    System.exit(0);
                } else {
                    randomNumber = random.nextInt(100);
                    System.out.println(randomNumber);
                    attempts = 0;
                }
            }
        }
    }
}

Answer 3

如果没有猜到正确的数字，它就会陷入无限循环。 我对您的代码做了一些改动，看看是否有帮助。

    package com.ananth.stackoverflow.help;

import java.awt.Color;
import java.util.Random;

import javax.swing.JOptionPane;
import javax.swing.UIManager;

public class RandomNumberGuesser {
    public static void main(String[] args) {
        UIManager m1 = new UIManager();
        Color g = Color.gray;
        Color lg = g.brighter();
        m1.put("OptionPane.background", lg);
        m1.put("Panel.background", lg);

        int x;
        for (x = 1; true; x++) {
            Random random = new Random();
            int randomNumber = random.nextInt(100);
            System.out.println(randomNumber);
            JOptionPane.showMessageDialog(null,
                    "This program will generate a random number from 0 to 100 which you have to guess.", "Number Guesser",
                    JOptionPane.INFORMATION_MESSAGE);
            String guess = getInputFromUser();
            int guess1 = Integer.parseInt(guess);

            int y;
            for (y = 1; true; y++) {
                if (guess1 > 100 || guess1 < 0) {
                    JOptionPane.showMessageDialog(null, "Guess is out of range!\nPlease enter valid input.",
                            "Invalid Input", JOptionPane.WARNING_MESSAGE);
                } else if (randomNumber == guess1) {
                    JOptionPane.showMessageDialog(null, "You guessed the number right!\nIt took you " + y
                            + " attempt(s) to guess it.", "Congratulations!", JOptionPane.INFORMATION_MESSAGE);
                    if (JOptionPane.showConfirmDialog(null, "Want to play again?", "Play again?", JOptionPane.YES_NO_OPTION) == JOptionPane.NO_OPTION) {
                        System.out.println("Play again soon!");
                        System.exit(0);
                    } else {
                        y = 0;
                        break;
                    }
                } else if (randomNumber > guess1) {
                    JOptionPane.showMessageDialog(null, "You guessed too low.\nGuess again!", "Your guess",
                            JOptionPane.INFORMATION_MESSAGE);
                    guess = getInputFromUser();
                    guess1 = Integer.parseInt(guess);
                } else if (randomNumber < guess1) {
                    JOptionPane.showMessageDialog(null, "You guessed too high.\nGuess again!", "Your guess",
                            JOptionPane.INFORMATION_MESSAGE);
                    guess = getInputFromUser();
                    guess1 = Integer.parseInt(guess);
                }
            }
        }
    }

    private static String getInputFromUser() {
        String guess = "";
        guess = JOptionPane.showInputDialog(null, "Guess a number.", "Guess", JOptionPane.QUESTION_MESSAGE);
        if (guess == null) {
            System.out.println("The user has terminated the program");
            System.exit(0);
        }
        return guess;
    }
}