java - 如果我关闭对话框，则会发生 NullPointerException。我该如何摆脱它？

Question

这个问题已经有答案了:

What is a NullPointerException, and how do I fix it? (12 个回答)

已关闭 7 年前。

我目前正在制作一个测验程序，但如果我在要求输入时关闭对话框，则会发生 NullPointerException。我如何让它做其他事情，比如显示一条短信并提示输入有效条目。

String qn_1_ans = JOptionPane.showInputDialog(
            null,
            "What is the answer for Question 1? \nPink \nBlue \nBlack \nRed",
            JOptionPane.OK_OPTION
    );

if (qn_1_ans.equals(qn_1_right_ans)) {
        JOptionPane.showMessageDialog(null,
                "Thats correct");
        Score = Score + 1;
    } else {
        JOptionPane.showMessageDialog(null,
                "Your answer is wrong. The correct answer is " +     qn_1_right_ans);
    }

Answer 1

我首先阅读 JavaDocs

Returns:
user's input, or null meaning the user canceled the input

已添加强调