How to check the input is an integer or not in Java? [duplicate]

Answer 1

If the user input is a String then you can try to parse it as an integer using parseInt method, which throws NumberFormatException when the input is not a valid number string:

try {

    int intValue = Integer.parseInt(stringUserInput));
}(NumberFormatException e) {
    System.out.println("Input is not a valid integer");
}

Answer 2

        String input = "";
        int inputInteger = 0;
        BufferedReader br    = new BufferedReader(new InputStreamReader (System.in));

        System.out.println("Enter the radious: ");
        try {
            input = br.readLine();
            inputInteger = Integer.parseInt(input);
        } catch (NumberFormatException e) {
            System.out.println("Please Enter An Integer");
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        float area = (float) (3.14*inputInteger*inputInteger);
        System.out.println("Area = "+area);

Answer 3

You can try this way

 String input = "";
 try {
   int x = Integer.parseInt(input); 
   // You can use this method to convert String to int, But if input 
   //is not an int  value then this will throws NumberFormatException. 
   System.out.println("Valid input");
 }catch(NumberFormatException e) {
   System.out.println("input is not an int value"); 
   // Here catch NumberFormatException
   // So input is not a int.
 } 

Answer 4

If you are getting the user input with Scanner, you can do:

if(yourScanner.hasNextInt()) {
    yourNumber = yourScanner.nextInt();
}

If you are not, you'll have to convert it to int and catch a NumberFormatException:

try{
    yourNumber = Integer.parseInt(yourInput);
}catch (NumberFormatException ex) {
    //handle exception here
}

Answer 5

Using Integer.parseIn(String), you can parse string value into integer. Also you need to catch exception in case if input string is not a proper number.

int x = 0;

try {       
    x = Integer.parseInt("100"); // Parse string into number
} catch (NumberFormatException e) {
    e.printStackTrace();
}

Answer 6

You can use try-catch block to check for integer value

for eg:

User inputs in form of string

try
{
   int num=Integer.parseInt("Some String Input");
}
catch(NumberFormatException e)
{
  //If number is not integer,you wil get exception and exception message will be printed
  System.out.println(e.getMessage());
}