Java I/O How to - Create a Console menu

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Question

We would like to know how to create a Console menu.

Answer

// www  . j a va  2 s.c  om
public class Main {

  public static void main(String[] args) {
    int swValue;
    System.out.println("|   MENU SELECTION DEMO    |");
    System.out.println("| Options:                 |");
    System.out.println("|        1. Option 1       |");
    System.out.println("|        2. Option 2       |");
    System.out.println("|        3. Exit           |");
    swValue = Keyin.inInt(" Select option: ");

    // Switch construct
    switch (swValue) {
    case 1:
      System.out.println("Option 1 selected");
      break;
    case 2:
      System.out.println("Option 2 selected");
      break;
    case 3:
      System.out.println("Exit selected");
      break;
    default:
      System.out.println("Invalid selection");
      break; // This break is not really necessary
    }
  }
}

class Keyin {

  //*******************************
  //   support methods
  //*******************************
  //Method to display the user's prompt string
  public static void printPrompt(String prompt) {
    System.out.print(prompt + " ");
    System.out.flush();
  }

  //Method to make sure no data is available in the
  //input stream
  public static void inputFlush() {
    int dummy;
    int bAvail;

    try {
      while ((System.in.available()) != 0)
        dummy = System.in.read();
    } catch (java.io.IOException e) {
      System.out.println("Input error");
    }
  }
  public static String inString() {
    int aChar;
    String s = "";
    boolean finished = false;

    while (!finished) {
      try {
        aChar = System.in.read();
        if (aChar < 0 || (char) aChar == '\n')
          finished = true;
        else if ((char) aChar != '\r')
          s = s + (char) aChar; // Enter into string
      }

      catch (java.io.IOException e) {
        System.out.println("Input error");
        finished = true;
      }
    }
    return s;
  }

  public static int inInt(String prompt) {
    while (true) {
      inputFlush();
      printPrompt(prompt);
      try {
        return Integer.valueOf(inString().trim()).intValue();
      }

      catch (NumberFormatException e) {
        System.out.println("Invalid input. Not an integer");
      }
    }
  }

}

The code above generates the following result.

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