如何捕捉字母并显示错误，除了整数？答案

【问题标题】：How to catch letters and display error and except only integers?如何捕捉字母并显示错误，除了整数？
【发布时间】：2020-03-08 20:11:24
【问题描述】：

对编码相当陌生，我只想接受整数并显示只允许使用整数的 JOptionPane 警告消息。我曾尝试使用 NumberFormatException 但我不熟悉这种方法。谢谢！

    import javax.swing.JOptionPane;
import java.util.Random;
public class GuessingGame
{
    public static void main(String[] args)
    {
        int start = JOptionPane.showConfirmDialog(null, "You must guess a number between 100 and 500 in a set amount of guesses.", "Press 'Yes' to start the guessing game.", JOptionPane.YES_NO_OPTION); 
        if(start == JOptionPane.YES_OPTION)
        {
            Random rng = new Random();
            int theNumber = rng.nextInt((500-100)+1)+100; 
            String guess;
            int maxAttempt = 1;
            int inputNumber;
            System.out.println(theNumber);
            while(maxAttempt<=4)
            {
                guess = JOptionPane.showInputDialog(null, "Please input a number between 100-500 you have four chances.");
                inputNumber = Integer.parseInt(guess);
                try
            {
            }catch(NumberFormatException e){
                JOptionPane.showMessageDialog(null, "You must only enter an integer", "Guessing Game", JOptionPane.WARNING_MESSAGE);
            }
                if(inputNumber==theNumber)
                {
                    JOptionPane.showMessageDialog(null, "Winner! Guess is correct.", "Guessing Game", JOptionPane.INFORMATION_MESSAGE);
                    break;
                }
                else if(inputNumber>theNumber)
                    JOptionPane.showMessageDialog(null, "Guess was greater than the real number.", "Guessing Game", JOptionPane.WARNING_MESSAGE);
                else
                    JOptionPane.showMessageDialog(null, "Guess was less than the real number.", "Guessing Game", JOptionPane.WARNING_MESSAGE);
                maxAttempt++;
            }

            if(maxAttempt>4)
                JOptionPane.showMessageDialog(null, "Game Over. You have exceeded your guessing limit.", "Guessing Game", JOptionPane.ERROR_MESSAGE);
        }
        else
            JOptionPane.showMessageDialog(null, "Quiting Game, press 'Ok' to exit.", "Guessing Game", JOptionPane.INFORMATION_MESSAGE);




    }
}

【问题讨论】：

您将try 放入while 循环中，在您接受第一个int 作为输入之前，它应该位于main() 方法的开头。
这能回答你的问题吗？ How to check if a String is numeric in Java

标签： java bluej

【解决方案1】：

您需要做的是在 try-catch 中调用 Integer#parseInt。那么当异常发生时，你需要继续进行while循环的下一次迭代。

替换

                inputNumber = Integer.parseInt(guess);
                try  {
                }catch(NumberFormatException e){
                    JOptionPane.showMessageDialog(null, "You must only enter an integer", "Guessing Game", JOptionPane.WARNING_MESSAGE);
                }

有

                try {
                    inputNumber = Integer.parseInt(guess);
                } catch (NumberFormatException e) {
                    JOptionPane.showMessageDialog(null, "You must only enter an integer", "Guessing Game", JOptionPane.WARNING_MESSAGE);
                    continue;
                }

【讨论】：