LotteryDrawing.java Source code

Introduction

Here is the source code for LotteryDrawing.java

Source

/*
 This program is a part of the companion code for Core Java 8th ed.
 (http://horstmann.com/corejava)
    
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
    
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
    
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import java.util.Arrays;
import java.util.Scanner;

/**
 * This program demonstrates array manipulation.
 * 
 * @version 1.20 2004-02-10
 * @author Cay Horstmann
 */
public class LotteryDrawing {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        System.out.print("How many numbers do you need to draw? ");
        int k = in.nextInt();

        System.out.print("What is the highest number you can draw? ");
        int n = in.nextInt();

        // fill an array with numbers 1 2 3 . . . n
        int[] numbers = new int[n];
        for (int i = 0; i < numbers.length; i++)
            numbers[i] = i + 1;

        // draw k numbers and put them into a second array
        int[] result = new int[k];
        for (int i = 0; i < result.length; i++) {
            // make a random index between 0 and n - 1
            int r = (int) (Math.random() * n);

            // pick the element at the random location
            result[i] = numbers[r];

            // move the last element into the random location
            numbers[r] = numbers[n - 1];
            n--;
        }

        // print the sorted array
        Arrays.sort(result);
        System.out.println("Bet the following combination. It'll make you rich!");
        for (int r : result)
            System.out.println(r);
    }
}