用户输入在同一行？

Question

I'm new to Java so forgive me. I'm writing a small little Guessing Game program.

import java.util.Scanner;

public class GuessingGame {

static Scanner userInput = new Scanner(System.in);

public static void main(String[] args) {
    int menuOption; 
    // Main Screen //
    System.out.println("Guessing Game");
    System.out.println("---------------------");
    System.out.println("1.) Play Game");
    System.out.println("2). Exit");
    System.out.println();           

    while (true) {
        System.out.print("Please select a menu option: ");                  
        menuOption = userInput.nextInt();

        if (menuOption == 2) {
            System.out.println("Exiting the game. Thanks for playing!");
            break; 

        } else if (menuOption == 1) {
            System.out.println("Let's start the game!");

            getRandomRange();

        } else {
                System.out.println("Sorry, that's not a valid option. Please try again.");
                continue;
        }
    }

}
/**
 * Determine the range of numbers to work with
 */
public static void getRandomRange() {
    int min;
    int max;

    System.out.print("Choose a minimum number: ");
    min = userInput.nextInt();

    System.out.print("Choose a maximum value: ");
    max = userInput.nextInt();

    getRandomNumber(min, max);
}

public static void getRandomNumber(int min, int max) {
    int randomNumber = (int) (Math.random() * (max - min + 1)) + min;

    getAGuess(min, max, randomNumber);
}

public static void getAGuess(int min, int max, int randomNumber) {
    int guess; 

    while (true) {
        System.out.print("Guess a number between " + min + " and " + (max) + ": ");
        guess = userInput.nextInt();

        if (guess == randomNumber) {
            System.out.println("Correct! The random number is: " + randomNumber);
            break;
        }
    }   
  }
}

When I prompt the user to guess a number and the number is incorrect, I want to be able to flush immediately flush the input stream and enter another guess on the same line.

For example: Guess a number between 0 and 5: I enter my guesses here on this one line only.

I could take the print out of the loop but in that case, if I enter an inccorect number, the cursor jumps to the next line.

Hope this makes sense. Thanks!

Answer 1

If your goal is only to clear the console, then you could do:

Runtime.getRuntime().exec("cls");

Or if you are on Linux or OS X:

Runtime.getRuntime().exec("clear");

Now if you add previous line that you wanted to keep, you will need to keep then in an Array and reprint after each clear.

This won't work in IDE's.

---

If you want a more system-independent way, there is a library named JLine ( GitHub ), which is designed for a better console usage. It actually contains a method clearScreen .

---

You could also do:

System.out.print("\033[H\033[2J");

This will clear the screen and return the cursor to the first row.

Answer 2

A quick and dirty solution...

public class Main {


    public static final void main(String[] data) {

        Scanner userInput = new Scanner(System.in);
        int min = 0;
        int max = 10;
        int randomNumber = (int) ((Math.random() * max) + (min + 1));

        while (true) {
            System.out.print("Guess a number between " + min + " and " + max + ": ");
            int guess = userInput.nextInt();
            if (guess == randomNumber) {
                System.out.println("Correct! The random number is: " + randomNumber);
                break;
            } else {
                for (int i = 0 ; i < 25; i++) {
                    System.out.println();
                }
            }
        } 
    }
}