Java Catch Exception - Empty String

Question

I'm looking for an exception on how to catch an invalid String that is user input. I have the following code for a exception on an integer input:

            try {
            price = Integer.parseInt(priceField.getText());
            }
            catch (NumberFormatException exception) { 
            System.out.println("price error");
            priceField.setText("");
            break;

But I'm not aware of a specific exception for strings, the input is a simple JTextBox so the only incorrect input I can think of is if the user enters nothing into the box, which is what I'm looking to catch.

JB Nizet · Accepted Answer · 2014-11-01 18:43:55Z

6

if (textField.getText().isEmpty())

is all you need.

Or maybe

if (textField.getText().trim().isEmpty())

if you also want to test for blank inputs, containing only white spaces/tabs.

You generally don't use exceptions to test values. Testing if a string represents an integer is an exception to the rule, because there is no available isInt() method in String.

answered Nov 1, 2014 at 18:43

JB Nizet

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Comments

Sundar Rajan · Accepted Answer · 2014-11-01 18:49:27Z

0

You can do like

if (priceField.getText().isEmpty()) 
  throw new Exception("priceField is not entered.");

answered Nov 1, 2014 at 18:49

Sundar Rajan

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Comments

Charlie · Accepted Answer · 2014-11-01 19:01:32Z

You could check if priceField contains a string by using this:

JTextField priceField;
int price;
try {
 // Check whether priceField.getText()'s length equals 0
 if(priceField.getText().getLength()==0) {
  throw new Exception();
 }
 // If not, check if it is a number and if so set price
 price = Integer.parseInt(priceField.getText());
} catch(Exception e) {
 // Either priceField's value's length equals 0 or
 // priceField's value is not a number

 // Output error, reset priceField and break the code
 System.err.println("Price error, is the field a number and not empty?");
 priceField.setText("");
 break;
}

When the if-statement is true (If the length of priceField.getText() is 0) an exception gets thrown, which will trigger the catch-block, give an error, reset priceField and break the code.

If the if-statement is false though (If the length of priceField.getText() is greater or lower than 0) it will check if priceField.getText() is a number and if so it sets price to that value. If it not a number, a NumberFormatException gets thrown, which will trigger the catch-block etc.

Let me know if it works.

Happy coding :) -Charlie

aidanmelen · Accepted Answer · 2015-08-20 16:35:54Z

0

if you want your exception to be thrown during the normal operation of the Java Virtual Machine, then you can use this

if (priceField.getText().isEmpty()) 
    throw new RunTimeException("priceField is not entered.");

answered Aug 20, 2015 at 16:35

aidanmelen

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