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Core java. Please help me catch a bug.

Posted on 2016-08-22
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Last Modified: 2016-08-31
To make story short, I simplify the code as much as possible.  Please help me to catch a bug. What do I miss ? I know about HashSet and I know how to use google. I'm interesting in my particular code.

package TaskChAll;

import java.util.Arrays;


public class Taskv4_interestingBUG2 {

    public static String removeAllDuplications(int[] initialArray) {
        int size = initialArray.length;
        System.out.println("Size before deletion: " + size);
        for (int i = 0; i < size; i++) {
            for (int j = i + 1; j < size; j++) {
                if (initialArray[i] == initialArray[j]) {   // step 1
                    while (j < (size) - 1) {    // inside this loop step 2
                        initialArray[j] = initialArray[j + 1];
                        j++;
                    }
                    size--; // step 3
                }
            }
        }
        int[] outputArray = new int[size]; // step 4
        for (int k = 0; k < size; k++) {
            outputArray[k] = initialArray[k];
        }
       // initialArray = outputArray;
        if (isThereDublication(outputArray)) {
            removeAllDuplications(outputArray);
        }
        return Arrays.toString(outputArray);
    }

    protected static boolean isThereDublication(int[] initialArray) {
        for (int i = 0; i < initialArray.length - 1; i++) {
            for (int j = i + 1; j < initialArray.length - 1; j++) {
                if ((initialArray[i] == initialArray[j]) && (i != j)) {
                    return true;
                }
            }
        }
        return false;
    }
}

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package TaskChAll;



public class Taskv4Test_interestingBUG2 {

    public static void main(String[] args) {
        testRemoveAllDuplications();
    }

    private static void testRemoveAllDuplications() {
        System.out.println("To pass the test enter number of elements '5'");
        int[] vectorWithDuplication = {4, 2, 53, 2, 53,53,53};

       //  String  expectedTestResults = "{4, 2, 53}";
        

        System.out.println(Taskv4_interestingBUG.removeAllDuplications(vectorWithDuplication)); 

       

    }
}

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0
Comment
Question by:SunnyX
5 Comments
 
LVL 8

Expert Comment

by:James Bilous
ID: 41765783
What are the symptoms of your problem? What is going wrong?
0
 

Author Comment

by:SunnyX
ID: 41765804
the output : [4, 2, 53, 53]

I don't know, I never saw such before. On debugging the code doing everything that I expect every assign  right output to the "outputArray" array. However, somehow reassign on the wrong one and return it. Please, copy past this code to the ide ( I tried intellij idea and eclipse both show wrong result ) take a look what happen during debugging , quite interesting.
0
 
LVL 14

Assisted Solution

by:CPColin
CPColin earned 350 total points
ID: 41765811
When you call removeAllDuplications() again, you're modifying the array you're passing into it, but you're not keeping track of the updated size of the array, so you're never actually discarding that last duplicate value.

Edit: Maybe.
0
 
LVL 35

Accepted Solution

by:
mccarl earned 150 total points
ID: 41766342
There are 3 problems with your code above...

- CPColin has found one of them, yes you have a call to the removeAllDuplications method (line 28) but you AREN'T doing anything with the return value. Add a   return   keyword in front of line 28 so that you return the String that it generates.

 - Now that alone won't change anything though. Why? Because in this particular test case, you aren't actually calling removeAllDuplicates the second time. That's because there is a problem in your isThereDublication method. You AREN'T checking the last element in the array and so it never sees the two 53's.  You need to remove the   " - 1"   after initialArray.length from the inner loop (line 25)

 - The above two steps will resolve the issues HOWEVER, I assume that you went to the trouble of doing the recursive removeAllDuplicates call because the first loop wasn't fully removing all duplicates. The EASIEST way to fix all this is to just do it properly in the first place. If you add a line     j = i;     just after line 18 above, your j variable will do the right thing and you will remove ALL the duplicates in one go. You can then delete lines 27 - 29, and then delete the extra method at lines 33 - 42.
1
 

Author Closing Comment

by:SunnyX
ID: 41778274
Thx!
0

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