Help to deal with the problem. I wrote a console menu with input validation using the loop do {} while (); but the input processing goes only after the second input - I can not understand what's the matter ...

public class Menu { public static void items() { String[] menuArray = { "Non-paired values 1-20", // 0 "Non-paired values 0-99 and 99-0", // 1 "Array with random values 0-9", // 2 "Array with random values 0-999 + print MIN/MAX", // 3 "Multi Array 8x5 with random values 10-99", // 4 "Multi Array 8x5 with MATRIX Format", // 5 "Loop counter", // 6 "Exit", // 7 "Choose your Menu item #>"}; // 8 for (int i = 0; i < menuArray.length; i++) { if (i < menuArray.length - 2) { System.out.println((i + 1) + ". " + menuArray[i]); } if ((i >= menuArray.length - 2) && (i < menuArray.length - 1)) { System.out.print("Type \'" + menuArray[i] + "\' to exit program!\n"); } if ((i >= menuArray.length - 1) && (i < menuArray.length)) { System.out.print(STAR_LINE + menuArray[i]); } } }} ----------------------------------- public static void main(String[] args) { boolean isExit = false; do { Menu.items(); Scanner scanner = new Scanner(System.in); if (scanner.nextLine().isEmpty()) { System.out.println("You didn't enter anything. Repeat please!"); } else { if (scanner.hasNextInt()) { int input = scanner.nextInt(); if ((input <= 0) || (input > 3)) { System.out.println("Choose item from 1-3"); } else { switch (input) { case 1: System.out.println("Entered number 1.\n"); break; case 2: System.out.println("Entered number 2.\n"); break; case 3: System.out.println("Entered number 3.\n"); break; } } } else { String inputString=scanner.nextLine(); if (inputString.equals("exit")) { isExit = true; }else { System.out.println("You entered STRING, please read menu instruction"); } } } }while (!isExit); }

    1 answer 1

    Because you tear out the whole line from the input so that it is entered into it:

     if (scanner.nextLine().isEmpty())...

    Make a

     if (!scanner.hasNextLine())...

    And then remove the empty input here:

     String inputString = scanner.nextLine(); if (inputString.equals("exit")) { isExit = true; } else if (inputString.isEmpty()) { System.out.println("You didn't enter anything. Repeat please!"); } else { System.out.println("You entered STRING, please read menu instruction"); }