'Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException' 当使用 Integer.parseInt - Java

Question

我正在尝试创建一个简单的猜数 GUI 游戏。我正在使用 'Integer.parseInt' 将用户的输入作为整数而不是字符串进行比较，以便进行比较。该程序仍按预期执行，但在控制台中出现以下错误：

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: ""
    at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:67)
    at java.base/java.lang.Integer.parseInt(Integer.java:678)
    at java.base/java.lang.Integer.parseInt(Integer.java:784)
    at Window.takeGuess(Window.java:58)
    at Window.actionPerformed(Window.java:32)
    at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1972)
    at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2313)
    at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
    at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
    at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)

第58行是使用Integer.parseInt命令的地方，第32行是调用takeGuess()函数的地方。我的代码如下所示：

public void takeGuess() {
        while (playing) {

            // retrieve input and convert to integer for comparison
            int guess = Integer.parseInt(txtGuess.getText());
            txtGuess.setText(null);

            // decide outcome of guess
            if (guess > number) {
                txtDescription.setText("Too high!");
            } else if (guess < number) {
                txtDescription.setText("Too low!");
            } else {
                win = true;
                txtDescription.setText("You win!");
                playing = false;
            }

            // increment guess counter then repeat if needed
            guessCount++;
            currentScore.setText("" + guessCount);
            System.out.println("received guess\n");
        }
    }

我最初将 txtGuess.setText(null) 设置为 txtGuess.setText("")，但它给出了同样的错误。正如我所说，尽管有这个错误，程序仍然可以运行，但我显然还是想修复它。有人可以帮忙吗？

Answer 1

这条评论帮助解决了问题：

Well, you're trying to parse an empty string as if it's an integer. It's not clear how you're calling takeGuess(), but it should probably only be in response to the user clicking a button or something like that - and it shouldn't be in a loop, otherwise you're not giving them a chance to change their guess before trying again. – Jon Skeet

我引入了一个名为 'lose' 的新布尔值，如果他们放弃，它会设置为 true。还将 while 循环更改为 if 语句，因此函数仅在 win = false 和 lose = false 时执行某些操作，即它们仍在播放。

public void takeGuess() {

    // cannot make a guess if won the game or given up
    if (!win && !lose) {

        // retrieve input and convert to integer for comparison
        int guess = Integer.parseInt(txtGuess.getText());
        txtGuess.setText(null);


        // decide outcome of guess
        if (guess > number) {
            txtDescription.setText("Too high!");
        } else if (guess < number) {
            txtDescription.setText("Too low!");
        } else {
            win = true;
            lose = false;
            txtDescription.setText("You win!");
        }

        // increment guess counter then repeat if needed
        guessCount++;
        currentScore.setText("" + guessCount);
        System.out.println("received guess\n");
    }

}

它不再循环回遇到要解析的空字符串，这给出了错误。

'Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException' 当使用 Integer.parseInt - Java

'Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException' when using Integer.parseInt - Java

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