how to remove duplicate array elements using hashmap in java

Question

How to remove duplicate elements in an array using HashMap without using hashset in java...

Below code describes removal of duplicates in array..

Now i need to write using hashmap for generating key and value pairs

import java.util.*;

class TestArray{

public static void main(String arg[])
{

ArrayList<String> wordDulicate = new ArrayList<String>();

    wordDulicate.add("chennai");
    wordDulicate.add("bangalore");
    wordDulicate.add("hyderabad");
    wordDulicate.add("delhi");
    wordDulicate.add("bangalore");
    wordDulicate.add("mumbai");
    wordDulicate.add("mumbai");
    wordDulicate.add("goa");
    wordDulicate.add("calcutta");
    wordDulicate.add("hyderabad");

    ArrayList<String> nonDupList = new ArrayList<String>();

    Iterator<String> dupIter = wordDulicate.iterator();
    while(dupIter.hasNext())
    {
    String dupWord = dupIter.next();
    if(nonDupList.contains(dupWord))
    {
        dupIter.remove();
    }else
    {
        nonDupList.add(dupWord);
    }
    }
  System.out.println(nonDupList);
}
  }

A simpler way to to what you did is to do new ArrayList<String>(wordDuplicate). What values do you want to store? — Tobias Ritzau
– Tobias Ritzau, Commented Oct 19, 2012 at 10:18

Marko Topolnik · Accepted Answer · 2012-10-19 10:16:34Z

3

A HashSet is implemented in terms of a HashMap anyway. If you specifically want to use a HashMap, use it the same way as HashSet does: use a dummy constant new Object() as the map value everywhere.

answered Oct 19, 2012 at 10:16

Marko Topolnik

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1 Comment

Marko Topolnik Over a year ago

I don't get your comment. My answer explains what to do without using HashSet. It is almost exactly the same advice as in the answer you accepted.

Jeroen Vuurens · Accepted Answer · 2012-10-19 10:22:30Z

0

Well a HashMap will prevent you from entering duplicate keys, the same way as HashSet. Actually, many implementations of HashSet just use a HashMap under the hood.

So you can do:

HashMap<String, String> map = new HashMap<String, String>();
for (String s : WordDuplicate) 
  map.put( s, s );

Now you can access the key/values just like a HashMap.

answered Oct 19, 2012 at 10:22

Jeroen Vuurens

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Stephen Rauch · Accepted Answer · 2018-04-26 04:16:00Z

0

import java.util.HashSet;
import java.util.Stack;

public class stackdupes {

    public static void main(String[] args) {
        Stack<Integer> st = new Stack<Integer>();
        int[] arr= {1,2,3,3,4,5,5,7};
        HashSet<Integer> set = new HashSet<Integer>();

        for (int i=0;i<arr.length;i++) {
            if(set.add(arr[i]) == true)
            st.push(arr[i]);
        }
        System.out.println(st); 

    }   
}

edited Apr 26, 2018 at 4:16

Stephen Rauch♦

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answered Apr 26, 2018 at 3:53

Niranjani raya

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