Java - Input Validation via Do While Loop

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Description

Input Validation via Do While Loop

Demo

import java.util.Scanner;

public class InputValidationDoWhile {
  
  public static void main(String args[]) {
    Scanner keyboard = new Scanner(System.in);
    int number;/* ww  w .  j ava  2 s  .c om*/
    boolean firstRun = true;

    // Get and validate the input.
    do {
      if (!firstRun) {// first time still true so basically saying that if not first run can print invalid msg.
        System.out.println("That number is invalid.");
      }

      System.out.print("Enter a number in the " + "range of 1 through 100: ");
      number = keyboard.nextInt();
      firstRun = false; // this makes false so from now on will be false and can now print invalid message
    } while (number < 1 || number > 100);
    keyboard.close();
  }
  
}