java - 如何防止用户使用 JOptionpane 输入字符、字符串和空格

Question

如何防止用户使用 JOptionPane 输入字符、字符串和空格？我在互联网上搜寻答案，但一无所获。请帮忙，我需要三天内完成。 这是我的代码:

int num, ctr, ctrodd=0, ctreven=0;
for (ctr=1;ctr<=15;ctr++)
{
    num=Integer.parseInt(JOptionPane.showInputDialog("Enter number "));

    if  (!num.hasNextInt()) 
    {
        JOptionPane.showMessageDialog(null,"That's not a number!");
        ctr--;
        num.next();
    }
    else if (num%2==0)
    {
        ctreven++;
    }
    else if (num%2==1)
    {
        ctrodd++;
    }
    ctr++;
}
JOptionPane.showMessageDialog(null,"Odd"+ctrodd+"\neven"+ctreven);

Answer 1

插入此内容:

 if  (!num.hasNextInt()) 
    {
    JOptionPane.showMessageDialog(null,"That's not a number!");
    ctr--;
    num.next();
    }

试试这个:

while (!num.hasNextInt()) 
{
JOptionPane.showMessageDialog(null,"That's not a number!");
num.next();
}