Index out of bound error varies when it shows

Question

I keep getting an Index out of bounds error when i run this program periodically. I notice it more when I enter a higher starting percentage like 80+. I know it has to do with the shotsMade ArrayList . But i am not sure what to do to correct it. Thanks.

    import java.util.*;

    public class Test {
    public static void main(String[] args) {
        int myGameCounter = 1;  
        List<Integer> shotsMade = new ArrayList<Integer>();
        shotsMade.add(0);
        System.out.print("Enter Player's Free Throw Percentage: ");
        Scanner input = new Scanner(System.in);
        int percent = input.nextInt();


        //Game #1
        System.out.println("Game " + myGameCounter + ":");
        Random r = new Random();
        myGameCounter++;
        for (int i = 0; i < 10; ++i){
            boolean in = tryFreeThrow(percent);
            if (in) {
            shotsMade.set(0, shotsMade.get(0)+1);
            System.out.print("In" + " ");
            }
            else {
            shotsMade.add(0);
            System.out.print("Out" + " ");
            }
        }
        System.out.println("");
        System.out.println("Free throws made: " + shotsMade.get(0) + " out of 10");
            //Game #2
        System.out.println("");
        System.out.println("Game" + myGameCounter + ":");
        myGameCounter++;
        for (int i = 0; i < 10; ++i){
            boolean in = tryFreeThrow(percent);
            if (in) {
            shotsMade.set(1, shotsMade.get(1)+1);
            System.out.print("In" + " ");
            }
            else {
            shotsMade.add(0);
            System.out.print("Out" + " ");
            }   
        }
        System.out.println("");
        System.out.println("Free throws made: " + shotsMade.get(1) + " out of 10");
            //Game #3
        System.out.println("");
        System.out.println("Game" + myGameCounter + ":");
        myGameCounter++;
        for (int i = 0; i < 10; ++i){
            boolean in = tryFreeThrow(percent);
            if (in) {
            shotsMade.set(2, shotsMade.get(2)+1);
            System.out.print("In" + " ");
            }
            else {
            shotsMade.add(0);
            System.out.print("Out" + " ");
            }   
        }
        System.out.println("");
        System.out.println("Free throws made: " + shotsMade.get(2) + " out of 10");
            //Game #4
        System.out.println("");
        System.out.println("Game" + myGameCounter + ":");
        myGameCounter++;
        for (int i = 0; i < 10; ++i){
            boolean in = tryFreeThrow(percent);
            if (in) {
            shotsMade.set(3, shotsMade.get(3)+1);
            System.out.print("In" + " ");
            }
            else {
            shotsMade.add(0);
            System.out.print("Out" + " ");
            }   
        }
        System.out.println("");
        System.out.println("Free throws made: " + shotsMade.get(3) + " out of 10");
            //Game #5
        System.out.println("");
        System.out.println("Game" + myGameCounter + ":");
        myGameCounter++;
        for (int i = 0; i < 10; ++i){
            boolean in = tryFreeThrow(percent);
            if (in) {
            shotsMade.set(4, shotsMade.get(4)+1);
            System.out.print("In" + " ");
            }
            else {
            shotsMade.add(0);
            System.out.print("Out" + " ");
            }   
        }
        System.out.println("");
        System.out.println("Free throws made: " + shotsMade.get(4) + " out of 10");

        System.out.println("");
        System.out.println("Summary:");


  }//main        



    public static boolean tryFreeThrow(int percent) {
        Random r = new Random();
        int number = r.nextInt(100);
        if (number > percent){ 
         return false;
        }
        return true;
    }






}//class    

Answer 1

Not run the code, but it looks like if you run the game and get 10 In's, followed by a In on the second game then you never add a second entry to the array list..

Therefore the second game will throw an IndexOutOfBoundsException when you call

shotsMade.set(1, shotsMade.get(1)+1);

in the second game

Answer 2

When you add to shotsMade you will add another entry at the end. If you set you will change one position:

so

 0 1 2 3 -> add(0) -> 0 1 2 3 0 0 1 2 3 -> set(2, 0) -> 0 1 0 3 

So if you want to call shotsMade.get(1) you need to miss once first because if you hit you use set and your list doesn't expand and is too short.