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".
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);
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.
4 Answers
Try this:
try{
Integer.valueOf(str);
} catch (NumberFormatException e) {
//not an integer
}
Try use instanceof , this method will help you with check between many types
Example
if (s instanceof String ){
// s is String
}else if(s instanceof Integer){
// s is Integer value
}
If you want just check between integer and string you can use @NKukhar code
try{
Integer.valueOf(str);
} catch (NumberFormatException e) {
//not an integer
}
try this
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");
}
}
Use a regex to validate the format of the string, and accept only numeric values on it:
Pattern.matches("/^\d+$/", numStr)
The matches method will return true if numString contains a valid numeric sequence, but of course the input can be way above an Integer's capacity. In that case, you can consider switching to a long or a BigInteger type.
