Question

Java:

Using ArrayLists to Simulate a Lottery Program

Simulate a Lottery Drawing by choosing 7 numbers at random from a pool containing 30 numbers

Each time a number is selected, it is recorded and removed from the pool

The pool values are 00 to 29 inclusive

1. Your program must output each selected number from the drawing using a two-digit format. For Example, the number 2 would be represented by 02 on the “Picked” line.   
2. The numbers drawn cannot repeat
3. Sort the picked numbers before printing them to the console
4. Show the initial and remaining pool
5. Your output must match as closely as possible to what is shown below

Example Output:

Initial Pool: [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29]

Picked: {01,06,09,19,25,26,27}

Remaining:[0,2,3,4,5,7,9,10,11,12,13,14,15,16,17,18,20,21,22,23,24,28,29]

Algorithm

1. Create two ArrayLists of type Integer called pool and pick
2. Create a Random Number to represent the number chosen, it will represent the index of the number chosen
3. Create the pool ArrayList by using a loop going from 0 to <30. Print the pool ArrayList Out
4. Choose 7 numbers at random, remove them from the pool ArrayList and place them in the picked ArrayList.
5. Use Collections.sort(pick) to sort the pick ArrayList<Integer>
6. Print the pick ArrayList out but add an additional 0 in the front if it is one digit. Example, change 2 to 02.
7. Print out the remaining pool after the numbers are picked.

Answer 1

CODE -

import java.util.ArrayList;

import java.util.Collections;

import java.util.Random;

public class lottry

{

    public static void main(String[] args)

    {

        Random rand = new Random();

        // Creating two ArrayLists of type Integer called pool and pick

        ArrayList<Integer> pool = new ArrayList<Integer>();

        ArrayList<Integer> pick = new ArrayList<Integer>();

        // Adding elements to the pool ArrayList

        for(int i=0; i<30; i++)

            pool.add(i);

        // Displaying the initial pool ArrayList

        System.out.print("Initial Pool: [" + pool.get(0));

        for(int i=1; i<30; i++)

            System.out.print(", " + pool.get(i));

        System.out.println("]");

        int i=0;

        // Choosing 7 random numbers

        while(i<7)

        {

            boolean found = false;

            int num = rand.nextInt(30);

            // Loop to check if random number generated is already in the ArrayList pick so that the numbers don't get repeated.

            for (int j=0; j<i; j++)

            {

                if(pick.get(j) == num)

                    found = true;

            }

            // Adding the choosen number to pool ArrayList and removing the number from the pool ArrayList

            if(!found)

            {

                pick.add(num);

                for(int j=0; j<30-i-1; j++)

                    if(pool.get(j) == num)

                        pool.remove(j);

                i++;

            }

        }

        // Sorting the pick ArrayList

        Collections.sort(pick);

        // Displaying the picked numbers

        System.out.printf("Picked: {%02d", pick.get(0));

        for (i=1; i<7; i++)

            System.out.printf(", %02d", pick.get(i));

        System.out.println("}");

        // Displaying the remaining pool ArrayList

        System.out.print("Remaining: [" + pool.get(0));

        for(i=1; i<23; i++)

            System.out.print(", " + pool.get(i));

        System.out.println("]");

    }

}

SCREENSHOTS -

CODE -

OUTPUT -

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