Why is my if statement not returning the correct result?

Question

Is there anything wrong with my code structure wise that is causing me to get errors? I think I fixed my for loops and the parameters and everything is fine now but I am still getting errors?

  public static int indexOf(int[] list, int searchValue) throws BadArrayException 
    {
        int indexValue = 0;

        if(list == null)
            throw new BadArrayException("Array is null");
        else if((list.length) == 0)
            return -1;

        for(int i = 0; i < (list.length); i++){
            if(list[i] == searchValue)
                indexValue = i;
        }
        return indexValue;
    }

    public static int lastIndexOf(int[] list, int searchValue) throws BadArrayException
    {
        int indexValue = 0;
        int last = (list.length-1);

        if(list.length == 0)
            return -1;

        for(int i = last; i >= 0; i--){
            if(list[i] == searchValue)
                indexValue = i;
        }
        return indexValue;        
    }
}

What I am getting:

Testing ArrayUtils class exception handling - 2/07/2014

--- Testing minValue method ---

Getting minVal of a null array OK - minValue threw exception for null array: BadArrayException

Getting minVal of an empty array OK - minValue threw exception for empty array: BadArrayException

Getting minVal() of: [10] OK - expected minValue to return 10 and got: 10

Getting minVal() of: [20,30] OK - expected minValue to return 20 and got: 20

Getting minVal() of: [40,30] OK - expected minValue to return 30 and got: 30

Getting minVal() of: [10,10] OK - expected minValue to return 10 and got: 10

Getting minVal() of: [15,25,35] OK - expected minValue to return 15 and got: 15

Getting minVal() of: [25,20,30] OK - expected minValue to return 20 and got: 20

Getting minVal() of: [50,40,30] OK - expected minValue to return 30 and got: 30

Getting minVal() of: [50,-10,40,-25,50,40,30] OK - expected minValue to return -25 and got: -25

Getting minVal() of: [200,50,-40,60,-15,30,75] OK - expected minValue to return -40 and got: -40

--- Testing copyRange method ---

Getting copyRange of a null array OK - copyRange threw exception for null array: BadArrayException

Getting copyRange(list,-1) of: [] OK - copyRange threw exception java.lang.ArrayIndexOutOfBoundsException: Array index out of range: -1

Getting copyRange(list,0) of: [] OK - copyRange copied the array correctly as []

Getting copyRange(list,1) of: [] OK - copyRange threw exception java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 1

Getting copyRange(list,-1) of: [20] OK - copyRange threw exception java.lang.ArrayIndexOutOfBoundsException: Array index out of range: -1

Getting copyRange(list,0) of: [20] OK - copyRange copied the array correctly as [20]

Getting copyRange(list,1) of: [20] OK - copyRange copied the array correctly as []

Getting copyRange(list,2) of: [20] OK - copyRange threw exception java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 2

Getting copyRange(list,-1) of: [10,15] OK - copyRange threw exception java.lang.ArrayIndexOutOfBoundsException: Array index out of range: -1

Getting copyRange(list,0) of: [10,15] OK - copyRange copied the array correctly as [10,15]

Getting copyRange(list,1) of: [10,15] OK - copyRange copied the array correctly as [15]

Getting copyRange(list,2) of: [10,15] OK - copyRange copied the array correctly as []

Getting copyRange(list,3) of: [10,15] OK - copyRange threw exception java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 3

Getting copyRange(list,-1) of: [30,35,40,45,50] OK - copyRange threw exception java.lang.ArrayIndexOutOfBoundsException: Array index out of range: -1

Getting copyRange(list,0) of: [30,35,40,45,50] OK - copyRange copied the array correctly as [30,35,40,45,50]

Getting copyRange(list,1) of: [30,35,40,45,50] OK - copyRange copied the array correctly as [35,40,45,50]

Getting copyRange(list,2) of: [30,35,40,45,50] OK - copyRange copied the array correctly as [40,45,50]

Getting copyRange(list,3) of: [30,35,40,45,50] OK - copyRange copied the array correctly as [45,50]

Getting copyRange(list,4) of: [30,35,40,45,50] OK - copyRange copied the array correctly as [50]

Getting copyRange(list,5) of: [30,35,40,45,50] OK - copyRange copied the array correctly as []

Getting copyRange(list,6) of: [30,35,40,45,50] OK - copyRange threw exception java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 6

--- Testing indexOf and lastIndexOf method ---

Getting indexOf of a null array OK - indexOf threw exception for null array: BadArrayException

Getting lastIndexOf of a null array ERROR - lastIndexOf threw an unexpected exception: java.lang.NullPointerException

Getting indexOf(5) of: [] OK - expected indexOf to return -1 and got: -1

Getting lastIndexOf(5) of: [] OK - expected lastIndexOf to return -1 and got: -1

Getting indexOf(20) of: [20] OK - expected indexOf to return 0 and got: 0

Getting indexOf(25) of: [20] ERROR - expected indexOf to return -1 but got: 0

Getting lastIndexOf(20) of: [20] OK - expected lastIndexOf to return 0 and got: 0

Getting lastIndexOf(25) of: [20] ERROR - expected lastIndexOf to return -1 but got: 0

Getting indexOf(5) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected indexOf to return 0 but got: 6

Getting indexOf(10) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected indexOf to return 1 but got: 7

Getting indexOf(15) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected indexOf to return 2 but got: 8

Getting indexOf(20) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected indexOf to return 3 but got: 9

Getting indexOf(0) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected indexOf to return -1 but got: 0

Getting lastIndexOf(5) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected lastIndexOf to return 6 but got: 0

Getting lastIndexOf(10) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected lastIndexOf to return 7 but got: 1

Getting lastIndexOf(15) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected lastIndexOf to return 8 but got: 2

Getting lastIndexOf(20) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected lastIndexOf to return 9 but got: 3

Getting lastIndexOf(0) of: [5,10,15,20,10,15,5,10,15,20] ERROR - expected lastIndexOf to return -1 but got: 0

Done - press enter key to end program

THESE SHOULD all be OK not errors Am I approaching this code incorrectly? Sorry I asked about this before but not in the correct manner

Answer 1

The code have three problems,

• The NULL validation over the parameter called list at lastIndexOf function, is missing. If you aggregate that validation you will avoid the error:

ERROR - lastIndexOf threw an unexpected exception: java.lang.NullPointerException

• For both functions, you must initialize the var indexValue with -1 instead of 0, to avoid:

ERROR - expected indexOf to return -1 but got: 0

• For both functions, once you find the first ocurrence of the searchValue you must return the index i. With this change you will avoid errors like:

ERROR - expected indexOf to return 2 but got: 8

With this three changes your code must look like this:

public static int indexOf(int[] list, int searchValue) throws BadArrayException 
{
    int indexValue = -1;

    if(list == null)
        throw new BadArrayException("Array is null");

    //Not neccessary
    /*else if((list.length) == 0)
        return -1;*/

    for(int i = 0; i < (list.length); i++){
        if(list[i] == searchValue)
            return i;
    }
    return indexValue;
}

public static int lastIndexOf(int[] list, int searchValue) throws BadArrayException
{
    int indexValue = -1;

    if(list == null)
        throw new BadArrayException("Array is null");

    int last = (list.length-1);

    //Not neccessary
    /*if(list.length == 0)
        return -1;*/

    for(int i = last; i >= 0; i--){
        if(list[i] == searchValue)
            return i;
    }
    return indexValue;        
}

Notice that some validation you made in your code are not anymore necessary if indexValue is initialized to -1.

Finally I recommend you to use some debugging tools or run your code with paper and pen, to discover the reasons of errors.

Hope to help you. Regards!

Answer 2

when you find the value, you should break from the loop:

    for(int i = 0; i < (list.length); i++){
        if(list[i] == searchValue) {
            indexValue = i;
            **break;**
        }
    }

Answer 3

One thing you are missing is null check of the array in lastIndexOf. But the main error is that you don't break out of the loop once you find the first match (this is true for both methods).

Oh, and int indexValue = 0; is wrong. You should initialize it to -1 (since that's the value that indicates "not found").

Taking all these things into account, I think this should work :

    public static int indexOf(int[] list, int searchValue) throws BadArrayException 
    {
        int indexValue = -1;

        if(list == null)
            throw new BadArrayException("Array is null");
        else if((list.length) == 0)
            return -1;

        for(int i = 0; i < (list.length); i++){
            if(list[i] == searchValue) {
                indexValue = i;
                break;
            }
        }
        return indexValue;
    }

    public static int lastIndexOf(int[] list, int searchValue) throws BadArrayException
    {
        int indexValue = -1;

        if(list == null)
            throw new BadArrayException("Array is null");

        int last = (list.length-1);

        if(list.length == 0)
            return -1;

        for(int i = last; i >= 0; i--){
            if(list[i] == searchValue) {
                indexValue = i;
                break;
            }
        }
        return indexValue;        
    }
}