remove duplicate value using collection framework

Question

I am trying to remove duplicate values by converting an array to an arraylist and then further converting the arraylist to a Hashset. As we know hashsets do not contain any duplicate values. But i am not getting any output. I am implementing this technique because I want to avoid using a for loop .

import java.util.*;

public class RemoveDupliucate {

public static void main(String[] args) {
    int a[]= {1,2,1,3,2,15,4,6,4};

    List l=Arrays.asList();

    TreeSet<Integer> m=new TreeSet(l);
    for(Integer i:m)
    {
        System.out.print(i);
    }



}

i am not getting any output.

[What is a debugger and how can it help me diagnose problems?](https://stackoverflow.com/q/25385173) — Andy Turner, Aug 06 '19 at 07:17
You don't do anything with `a`. You are constructing an empty list, copying it into a `TreeSet`, and then looping over the `TreeSet`, which is, of course, empty, so the loop body is never executed. (And `Arrays.asList(a)` isn't what you want to use, either). — Andy Turner, Aug 06 '19 at 07:18
Please avoid naming variable with a single character, especially “l”. Some font will display ‘l’ and “1” nearly the same — tiboo, Aug 06 '19 at 08:20

score 2 · Answer 1 · answered Aug 06 '19 at 07:26

If you want to remove duplicate elements from an array, there is already a method using java 8 stream,

Arrays.stream('array').distinct().toArray();

Which will remove all the duplicate elements and return the array.

for your code,

int a[]= {1,2,1,3,2,15,4,6,4};

a = Arrays.stream(a).distinct().toArray();

this should work, if you want to remove duplicates.

score 1 · Answer 2 · edited Aug 06 '19 at 08:27

1

This line will create an empty list, that’s why you got no output:

List l = Arrays.asList();

It should be something like

List<Integer> l = Arrays.asList(1,2,1,3,2,15,4,6,4);

edited Aug 06 '19 at 08:27

lolacoco

101
8

answered Aug 06 '19 at 08:08

tiboo

8,213
6
33
43

Or `Arrays.asList(a)` – dan1st Aug 06 '19 at 08:29

score 0 · Answer 3 · answered Aug 06 '19 at 07:35

It is very easy in Java 8 streams

int array[]= {1,2,1,3,2,15,4,6,4};

//Use Java 8 Streams to get distinct values from an array 
int[] unique = Arrays.stream(array).distinct().toArray();

If you don't want to use Java 8 streams API you can try in below Converting array into set

public void printDistinctElements(int[] inputArray)
{
    Set<Integer> elementSet = new HashSet<Integer>();

    for(int i = 0; i<inputArray.length; i++)
    {
        elementSet.add(inputArray[i]);
    }

    System.out.println("Distinct Elements");
    for (int i : elementSet) {
        System.out.print(" " +i);
    }
}

remove duplicate value using collection framework

3 Answers3