How to find duplicates in a java array using only for, if or while?

Question

can someone explain me how to find duplicate elements in java: array {1,5,7,4,5,1,8,4,1} using only for, if or while/do while?

Tnx in advance.

Dacha

• Alexis C.: Maybe you need to think about this alone before asking? Try with a pen and paper, what would you do?
• Dacha: I have problem counting duplicates that are repeated more than 2 times. I need to count duplicate element only one time. For exemple, element 1 appears 3 time but in fact it is one duplicate.
• Dacha: for(int i=0;i<array.length;i++) for(int j=i+1;j<array.length;j++) if(array[i]==array[j]) dupelement++
• Dacha: This only works if elements in arrays repeats 2 times.

Answer 1

Before you insert an element in the array, check first the content of the array. If the inserting object is equal to any then do not proceed with the insert.

Or maybe try this one:

int[] arrayObject={1,5,7,4,5,1,8,4,1};
List<Integer> uniqueList=new LinkedList<>();
List<Integer> duplicateList=new LinkedList<>();
for(int i=0; i<arrayObject.length; i++){
 if(!uniqueList.contains(arrayObject[i])){
 uniqueList.add(arrayObject[i]);
 }else if(!duplicateList.contains(arrayObject[i])){
 duplicateList.add(arrayObject[i]);
 }
}
System.out.println("Elements without duplicates: "+uniqueList);
System.out.println("Duplicated elements: "+duplicateList);

Output:
Elements without duplicates: {1, 5, 7, 4, 8}
Duplicated elements: {1, 5, 4}

• Dacha: Yes, I write that logic on paper but I have problem implement it in java code. I stuck somewhere in for loop.
• Dacha: Tnx MarionJeff for help
• marion-jeff: Accept it as the official answer by clicking the star