Java编程：当我输入一个数字并检查数字是否正确时，我遇到了一个问题_Java

Java编程：当我输入一个数字并检查数字是否正确时，我遇到了一个问题

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Java编程：当我输入一个数字并检查数字是否正确时，我遇到了一个问题,java,Java,我创建了一个丹麦游戏，你可以猜1-10之间的数字当我输入一个数字来检查我的猜测是否正确时，控制台中就会出现一个错误当我输入一个数字并检查数字是否正确时，你知道为什么会出现问题吗 Game.java import java.util.Random; public class Game { int randomNumber; public Game() { // Set randomNumber to randon number [1;10]

我创建了一个丹麦游戏，你可以猜1-10之间的数字

当我输入一个数字来检查我的猜测是否正确时，控制台中就会出现一个错误

当我输入一个数字并检查数字是否正确时，你知道为什么会出现问题吗

Game.java

import java.util.Random;

public class Game {
    int randomNumber;

    public Game() {
        // Set randomNumber to randon number [1;10]
        Random rand = new Random();
        randomNumber = rand.nextInt(10) + 1;
    }

    public int getRandomNumber() {
        return randomNumber;
    }

}

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

public class GameFrame extends JFrame implements ActionListener{
    private Game game;
    private Player player;
    private JTextField inputField;
    private JLabel gameAnswer, tries;

    public GameFrame(String title) {
        super(title);
        getContentPane().setLayout(new FlowLayout());
        setSize(300, 100);

        // Start game & add player
        game = new Game();
        player = new Player();

        addComponents();

        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

    }

    private void addComponents() {
        JLabel tries = new JLabel("Forsøg: " + player.getTries());
        getContentPane().add(tries);

        inputField = new JTextField(8);
        getContentPane().add(inputField);

        JButton submitGuess = new JButton("Gæt tal");
        submitGuess.addActionListener(this);
        getContentPane().add(submitGuess);

        JLabel gameAnswer = new JLabel("Gæt et tal mellem 1-10");
        getContentPane().add(gameAnswer);
    }

    private void resetGame() {
        // Create new randon number & new player
        game = new Game();
        player = new Player();

        // Set default text in components
        gameAnswer.setText("Gæt et tal mellem 1-10");
        tries.setText("Forsøg: " + player.getTries());
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // Increment tries guessed
        player.addTry();
        tries.setText("Forsøg: " + player.getTries());


        // Extract number guessed
        String textEntered = inputField.getText();
        int numberEntered = Integer.parseInt(textEntered);

        // How was it compared to randomNumber?
        if (numberEntered == game.getRandomNumber()) {
            // CORRECT! - display optionpane
            JOptionPane.showMessageDialog(null, "TILLYKKE! Du gættede rigtigt! Du brugte: " + player.getTries() + " forsøg.");

            // Reset Game
            resetGame();

        } else if (numberEntered > game.getRandomNumber()) 
            // To high
            gameAnswer.setText("Forket! Du gættede for højt!");
         else if (numberEntered < game.getRandomNumber()) 
            // To low
            gameAnswer.setText("Forkert! Du gættede for lavt!");

        // Calculate result & display
    }

public class Main {

    public static void main(String[] args) {
        new GameFrame("Gæt et tal");
    }
}

public class Player {
    private int tries;

    public Player() {
        tries = 0;
    }

    public void addTry() {
        tries++;
    }

    public int getTries() {
        return tries;
    }
}

GameFrame.java

import java.util.Random;

public class Game {
    int randomNumber;

    public Game() {
        // Set randomNumber to randon number [1;10]
        Random rand = new Random();
        randomNumber = rand.nextInt(10) + 1;
    }

    public int getRandomNumber() {
        return randomNumber;
    }

}

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

public class GameFrame extends JFrame implements ActionListener{
    private Game game;
    private Player player;
    private JTextField inputField;
    private JLabel gameAnswer, tries;

    public GameFrame(String title) {
        super(title);
        getContentPane().setLayout(new FlowLayout());
        setSize(300, 100);

        // Start game & add player
        game = new Game();
        player = new Player();

        addComponents();

        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

    }

    private void addComponents() {
        JLabel tries = new JLabel("Forsøg: " + player.getTries());
        getContentPane().add(tries);

        inputField = new JTextField(8);
        getContentPane().add(inputField);

        JButton submitGuess = new JButton("Gæt tal");
        submitGuess.addActionListener(this);
        getContentPane().add(submitGuess);

        JLabel gameAnswer = new JLabel("Gæt et tal mellem 1-10");
        getContentPane().add(gameAnswer);
    }

    private void resetGame() {
        // Create new randon number & new player
        game = new Game();
        player = new Player();

        // Set default text in components
        gameAnswer.setText("Gæt et tal mellem 1-10");
        tries.setText("Forsøg: " + player.getTries());
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // Increment tries guessed
        player.addTry();
        tries.setText("Forsøg: " + player.getTries());


        // Extract number guessed
        String textEntered = inputField.getText();
        int numberEntered = Integer.parseInt(textEntered);

        // How was it compared to randomNumber?
        if (numberEntered == game.getRandomNumber()) {
            // CORRECT! - display optionpane
            JOptionPane.showMessageDialog(null, "TILLYKKE! Du gættede rigtigt! Du brugte: " + player.getTries() + " forsøg.");

            // Reset Game
            resetGame();

        } else if (numberEntered > game.getRandomNumber()) 
            // To high
            gameAnswer.setText("Forket! Du gættede for højt!");
         else if (numberEntered < game.getRandomNumber()) 
            // To low
            gameAnswer.setText("Forkert! Du gættede for lavt!");

        // Calculate result & display
    }

public class Main {

    public static void main(String[] args) {
        new GameFrame("Gæt et tal");
    }
}

public class Player {
    private int tries;

    public Player() {
        tries = 0;
    }

    public void addTry() {
        tries++;
    }

    public int getTries() {
        return tries;
    }
}

Player.java

import java.util.Random;

public class Game {
    int randomNumber;

    public Game() {
        // Set randomNumber to randon number [1;10]
        Random rand = new Random();
        randomNumber = rand.nextInt(10) + 1;
    }

    public int getRandomNumber() {
        return randomNumber;
    }

}

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

public class GameFrame extends JFrame implements ActionListener{
    private Game game;
    private Player player;
    private JTextField inputField;
    private JLabel gameAnswer, tries;

    public GameFrame(String title) {
        super(title);
        getContentPane().setLayout(new FlowLayout());
        setSize(300, 100);

        // Start game & add player
        game = new Game();
        player = new Player();

        addComponents();

        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

    }

    private void addComponents() {
        JLabel tries = new JLabel("Forsøg: " + player.getTries());
        getContentPane().add(tries);

        inputField = new JTextField(8);
        getContentPane().add(inputField);

        JButton submitGuess = new JButton("Gæt tal");
        submitGuess.addActionListener(this);
        getContentPane().add(submitGuess);

        JLabel gameAnswer = new JLabel("Gæt et tal mellem 1-10");
        getContentPane().add(gameAnswer);
    }

    private void resetGame() {
        // Create new randon number & new player
        game = new Game();
        player = new Player();

        // Set default text in components
        gameAnswer.setText("Gæt et tal mellem 1-10");
        tries.setText("Forsøg: " + player.getTries());
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // Increment tries guessed
        player.addTry();
        tries.setText("Forsøg: " + player.getTries());


        // Extract number guessed
        String textEntered = inputField.getText();
        int numberEntered = Integer.parseInt(textEntered);

        // How was it compared to randomNumber?
        if (numberEntered == game.getRandomNumber()) {
            // CORRECT! - display optionpane
            JOptionPane.showMessageDialog(null, "TILLYKKE! Du gættede rigtigt! Du brugte: " + player.getTries() + " forsøg.");

            // Reset Game
            resetGame();

        } else if (numberEntered > game.getRandomNumber()) 
            // To high
            gameAnswer.setText("Forket! Du gættede for højt!");
         else if (numberEntered < game.getRandomNumber()) 
            // To low
            gameAnswer.setText("Forkert! Du gættede for lavt!");

        // Calculate result & display
    }

public class Main {

    public static void main(String[] args) {
        new GameFrame("Gæt et tal");
    }
}

public class Player {
    private int tries;

    public Player() {
        tries = 0;
    }

    public void addTry() {
        tries++;
    }

    public int getTries() {
        return tries;
    }
}

您声明了

private JLabel gameAnswer，尝试

作为类字段，但从不初始化它，因为在

addComponents（）

方法中，您可以使用以下命令声明和初始化新对象：

JLabel tries = new JLabel("Forsøg: " + player.getTries());
JLabel gameAnswer = new JLabel("Gæt et tal mellem 1-10");

所以您得到了

NullPointerException

。您需要像这样声明：

tries = new JLabel("Forsøg: " + player.getTries());
gameAnswer = new JLabel("Gæt et tal mellem 1-10");

它应该可以工作。

请生成一个小的描述性代码，让您认为它不起作用。读取整个代码是不可能的。另外，请告诉我们您在控制台中遇到的错误。您好，欢迎使用SO。请不要链接到你的代码，在问题中插入一个完整的例子，这样如果链接断开，用户仍然可以看到代码。