This exercise creates an array list of random numbers for a lottery draw.
My Code
Main
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
LotteryNumbers lotteryNumbers = new LotteryNumbers();
ArrayList<Integer> numbers = lotteryNumbers.numbers();
System.out.println("Lottery numbers:");
for (int number : numbers) {
System.out.print(number + " ");
}
System.out.println("");
}
}LotteryNumbers
import java.util.ArrayList;
import java.util.Random;
public class LotteryNumbers {
private ArrayList<Integer> numbers;
private Random random = new Random();
public LotteryNumbers() {
// Draw numbers as LotteryNumbers is created
this.numbers = new ArrayList<Integer>();
this.drawNumbers();
this.random = new Random();
}
public ArrayList<Integer> numbers() {
return this.numbers;
}
public void drawNumbers() {
// We'll format a list for the numbers
this.numbers = new ArrayList<Integer>();
// Write the number drawing here using the method containsNumber()
while (this.numbers.size() < 7){
int draw = this.random.nextInt(39) + 1;
if (!containsNumber(draw)){
this.numbers.add(draw);
}
}
}
public boolean containsNumber(int number) {
// Test here if the number is already in the drawn numbers
if (numbers.contains(number)){
return true;
}
return false;
}
}
Model Code
Main
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
LotteryNumbers lotteryNumbers = new LotteryNumbers();
ArrayList<Integer> numbers = lotteryNumbers.numbers();
System.out.println("Lottery numbers:");
for (int number : numbers) {
System.out.print(number + " ");
}
System.out.println("");
}
}LotteryNumbers
import java.util.ArrayList;
import java.util.Random;
public class LotteryNumbers {
private ArrayList<Integer> numbers;
public LotteryNumbers() {
// Draw numbers as LotteryNumbers is created
this.drawNumbers();
}
public ArrayList<Integer> numbers() {
return this.numbers;
}
public void drawNumbers() {
// We'll format a list for the numbers
this.numbers = new ArrayList<Integer>();
// Write the number drawing here using the method containsNumber()
Random random = new Random();
while (this.numbers.size() < 7) {
int newNumber = random.nextInt(39) + 1;
boolean alreadyDrawn = this.containsNumber(newNumber);
// we add the number only if it is not already among the drawn numbers
if (!alreadyDrawn) {
this.numbers.add(newNumber);
}
}
}
public boolean containsNumber(int number) {
// Test here if the number is already in the drawn numbers
for (int n : this.numbers) {
if (n == number) {
return true;
}
}
return false;
}
}Comments
I had a lot of trouble with the arraylist size. That the arraylist size changes depending on whether the numbers are a single or double digit is somewhat bizarre as well.