Below code snippets shows how to remove duplicate integers from an array without using any collections such as HashSet, ArrayList etc...
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public class UniqueElementinAnArray
{
public static void main(String[] args)
{
int[] a = {10,10,10,10,10,100};
int[] output = new int[a.length];
int count = 0;
int num = 0;
//Iterate over an array
for(int i=0; i<a.length; i++)
{
num=a[i];
boolean flag = check(output,num);
if(flag==false)
{
output[count]=num;
++count;
}
}
//print the all the elements from an array except zero's (0)
for (int i : output)
{
if(i!=0 )
System.out.print(i+" ");
}
}
/***
* If a next number from an array is already exists in unique array then return true else false
* @param arr Unique number array. Initially this array is an empty.
* @param num Number to be search in unique array. Whether it is duplicate or unique.
* @return true: If a number is already exists in an array else false
*/
public static boolean check(int[] arr, int num)
{
boolean flag = false;
for(int i=0;i<arr.length; i++)
{
if(arr[i]==num)
{
flag = true;
break;
}
}
return flag;
}
}

Robert Harvey
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Avinash Pande
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I am telling without using any collections. please read question properly. You have given reference of a question which has most of the answers are irrelevant. check those answers. I checked thats the reason I have added new question. – Avinash Pande Apr 19 '18 at 14:16
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2Then let my ask you a question: where do you **remove** anything from the given array? the array remains the same...you're just printing values. clearly not solved the task at hand – UninformedUser Apr 19 '18 at 14:18
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Sir, please execute above code using any java editor you will get to see. – Avinash Pande Apr 19 '18 at 14:19
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2Formally, you're creating a new array and always check whether the value already exists in, if not add the value - that's neither overwhleming nor black magic. Now the interesting part: How did you measure efficiency compared to other methods? Any benchmarks? – UninformedUser Apr 19 '18 at 14:22
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I didn't used any collections so all the data resides in stack only. it improves efficiency. – Avinash Pande Apr 19 '18 at 14:24