How Can I Correctly Identify Duplicate Integers in a Java Array?

Java Array, Finding Duplicates

Problem:
In Java, an array of integers is given, and the goal is to identify and report any duplicate elements within the array. However, a current approach to detecting duplicates yields an incorrect result when no duplicates exist.

Original Code:

int[] zipcodelist = // ...

boolean duplicates = false;
for(j = 0; j < zipcodeList.length; j++){
    for(k = 0; k < zipcodeList.length; k++){
        if (zipcodeList[k] == zipcodeList[j]){
            duplicates = true;
        }
    }
}

Issue in the Original Code:
The issue arises when there are no duplicates within the array. The loop structure assigns duplicates as true even in this scenario because the inner loop checks the equality between each element and itself. Therefore, when there are no duplicates, duplicates ends up being true.

Improved Code to Detect Duplicates:
To address this issue, the code can be modified as follows:

duplicates = false;
for (j = 0; j < zipcodeList.length; j++){
    for (k = j + 1; k < zipcodeList.length; k++){
        if (k != j && zipcodeList[k] == zipcodeList[j]){
            duplicates = true;
        }
    }
}

Explanation:
This modified code includes an additional condition (k != j) within the inner loop. This step ensures that the comparison is only performed between unique elements, avoiding the duplicate check of each element with itself. Consequently, duplicates will only be set to true when genuine duplicates are encountered, yielding an accurate result.

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