How do I test an array to find if there's a certain value in it?

Question

The problem requires me to: test the given array(s) and see if there's number 5 in it. If there is a 5, return False. Otherwise, return true. I got it to work... well, I know it's not in an efficient way. The only problem is that in case 1 and 6 I got:Error java.lang.ArrayIndexOutOfBoundsException, and I don't even know why. The rest works just fine.

import java.util.*;

public class testCases
{
    public static void main(String[] args)
    {
        Scanner kb = new Scanner(System.in);

        System.out.print("Which case do you wish to test? ");

        int testCase = kb.nextInt();

        switch(testCase)
        {
            case 1:
                    System.out.println("noFives(1, 2, 3, 4) = " + noFives(1, 2, 3, 4, 6));
                    break;

            case 2:
                    System.out.println("noFives(1, 2, 3, 4, 5) = " + noFives(1, 2, 3, 4, 5));
                    break;

            case 3:
                    System.out.println("noFives(1, 2, 5, 3, 4) = " + noFives(1, 2, 5, 3, 4));
                    break;

            case 4:
                    System.out.println("noFives(5, 1, 2, 3, 4) = " + noFives(5, 1, 2, 3, 4));
                    break;
            case 5:
                    System.out.println("noFives(27, 82, 4, 71, 6, 23, 9, 18) = " + noFives(27, 82, 4, 71, 6, 23, 9, 18));
                    break;

            case 6:
                    System.out.println("noFives(0) = " + noFives(0));
                    break;

            case 7:
                    System.out.println("noFives(5) = " + noFives(5));
                    break;

            default:
                    System.out.println("noFives() = " + noFives());

        }

    }

    public static boolean noFives(int ... n)
    {

        if(n.length == 0)
        return true;

        else if(n[0] == 5 || n[1] == 5 || n[2] == 5 || n[3] == 5 || n[4] == 5 || n[5] == 5 || n[6] == 5 || n[7] == 5)
        return false;

        else
        return true;

    }

}

`Arrays.stream(array).filter(x -> x == 5).collect(Collectors.toList).size() == 0` ? — Nir Alfasi, Nov 20 '17 at 06:22
@apples you could just iterate the array using a for loop it is simple — Robert Ellis, Nov 20 '17 at 06:23

score 0 · Answer 1 · answered Nov 20 '17 at 06:26

A few factors play into the inconsistent behavior of your implementation:

The || operator short-circuits. I.e., in noFives() if n[0] == 5, it doesn't test any of the other terms.
In java, accessing an element beyond the end of an array causes the OutOfBounds exception.

so you get the exception when the chain of || operations doesn't short-circuit before accessing an index outside of the array. Cases 1 and 6 have no fives to cause this short-circuit.

score 0 · Answer 2 · answered Nov 20 '17 at 06:28

You should use a loop to handle changing lengths of n. Rewriting your code

import java.util.*;

public class testCases
{
    public static void main(String[] args)
    {
        Scanner kb = new Scanner(System.in);

        System.out.print("Which case do you wish to test? ");

        int testCase = kb.nextInt();

        switch(testCase)
        {
            case 1:
                    System.out.println("noFives(1, 2, 3, 4) = " + noFives(1, 2, 3, 4, 6));
                    break;

            case 2:
                    System.out.println("noFives(1, 2, 3, 4, 5) = " + noFives(1, 2, 3, 4, 5));
                    break;

            case 3:
                    System.out.println("noFives(1, 2, 5, 3, 4) = " + noFives(1, 2, 5, 3, 4));
                    break;

            case 4:
                    System.out.println("noFives(5, 1, 2, 3, 4) = " + noFives(5, 1, 2, 3, 4));
                    break;
            case 5:
                    System.out.println("noFives(27, 82, 4, 71, 6, 23, 9, 18) = " + noFives(27, 82, 4, 71, 6, 23, 9, 18));
                    break;

            case 6:
                    System.out.println("noFives(0) = " + noFives(0));
                    break;

            case 7:
                    System.out.println("noFives(5) = " + noFives(5));
                    break;

            default:
                    System.out.println("noFives() = " + noFives());

        }

    }

    public static boolean noFives(int ... n)
    {

        if(n.length == 0)
        return true;

        else {
            for(int i=0; i < n.length; i++){
                if(n[i] == 5)
                    return false;
            }
        }

        return true;

    }

}

score 0 · Answer 3 · answered Nov 20 '17 at 06:29

This is due to the parameters being sent to the method noFives(int.. n) for case statement 1 you are passing 5 parameters

case 1:
                System.out.println("noFives(1, 2, 3, 4) = " + noFives(1, 2, 3, 4, 6));
                break;

whereas in noFives(int... n) method you are checking for index more than 5 hence ArrayIndexOutOfBoundsException

 else if (n[0] == 5 || n[1] == 5 || n[2] == 5 || n[3] == 5 || n[4] == 5 || n[5] == 5 || n[6] == 5 || n[7] == 5)

i would suggest you to change the method noFives(int ..n) like:

public static boolean noFives(int... n) {

        if (n.length == 0)
            return true;

        for (int i = 0; i < n.length ; i++) {
            if (n[i] == 5){
                return false;
            }
        }
        return true;
    }

How do I test an array to find if there's a certain value in it?

3 Answers3