Java：检测变量是String还是Integer [英] Java: Detecting if a variable is a String or an Integer

问题描述

我正在为我的一些家庭作业寻求帮助。我希望用户输入数字字符串，然后将其转换为整数。但是我想制作一个循环来检测用户是否输入了错误的值，例如One Hundred和100。

I'm look for some help on a bit of homework I have. I want the user to enter a numerical String, then convert it to an Integer. But I want to make a loop that will detect if the user entered in the wrong value such as "One Hundred" as apposed to "100".

我的想法是做这样的事情：

What I was thinking was to do something like this:

    do{
        numStr = JOptionPane.showInputDialog("Please enter a year in numarical form:"
                        + "\n(Ex. 1995):");
        num = Integer.parseInt(numStr);
            if(num!=Integer){
            tryagainstr=JOptionPane.showInputDialog("Entered value is not acceptable."
                                  + "\nPress 1 to try again or Press 2 to exit.");
    tryagain=Integer.parseInt(tryagainstr);
            }
            else{
            *Rest of the code...*
            }
            }while (tryagain==1);

但我不知道如何定义整数值。我基本上想要看看它是否是一个数字，以防止它在用户输入错误的东西时崩溃。

But I don't know how to define that "Integer" value. I essentially want it to see if it is a number or not to prevent it from crashing if the user enters the wrong thing.

推荐答案

试试这个

int num;
String s = JOptionPane.showInputDialog("Enter a number please");
while(true)
{
    if(s==null) 
        break; // if you press cancel it will exit
    try {
        num=Integer.parseInt(s);
        break;
    } catch(NumberFormatException ex)
    {
        s = JOptionPane.showInputDialog("Not a number , Try Again");
    }
}

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