Avoiding printing of duplicates in ArrayList

Question

I have one array list contains object( id,name).need to remove if duplicate names in the list

I need to print only name once if it is repeating

I can't read bold letters. And now I don't see any question there. — Rohit Jain, Dec 18 '12 at 07:20
When the title of your question is longer than your body, chances are you're a.) putting too much info into your title **and** b.) don't have enough information in your body. — Joachim Sauer, Dec 18 '12 at 07:29

score 3 · Answer 1 · answered Dec 18 '12 at 07:32

3

Use SET if you want don't want duplicate entries in your list:

HashSet if you don't required sequence
LinkedHashSet if you need to print name in sequence

Note: You must override equals and hashcode in object(ID,Name) otherwise you will find duplicate object in SET

answered Dec 18 '12 at 07:32

Rahul Gakhar

86
4

thanks...i have used set to remove the repeated value ..its works fine now – Rahul Dec 18 '12 at 08:05

score 0 · Answer 2 · answered Dec 18 '12 at 07:25

0

public static boolean checkDuplicate(ArrayList list) {
 HashSet set = new HashSet();
 for (int i = 0; i < list.size(); i++) {
  boolean val = set.add(list.get(i));
  if (val == false) {
    return val;
  }
 }
 return true;
}

answered Dec 18 '12 at 07:25

Mohammod Hossain

4,134
2
26
37

score 0 · Answer 3 · answered Dec 18 '12 at 07:27

Use a java.util.Set instead. It cannot contain duplicates.

Reference: http://docs.oracle.com/javase/6/docs/api/java/util/Set.html

Set<String> myNames = new HashSet<String>();
myNames.add("JAMES");
myNames.add("ELLA");
myNames.add("JAMES");

myNames.size() // will return 2

score 0 · Answer 4 · answered Dec 18 '12 at 07:29

0

Use a Set data structure with implementing appropriate Comparator. Run a loop and put your objects in that set. Print this set.

answered Dec 18 '12 at 07:29

Vallabh Patade

4,960
6
31
40

score 0 · Answer 5 · answered Dec 18 '12 at 07:32

Arraylist provides an iterator that allows to delete the last element returned by the iterator from the list itself. So we just keep track of the names that we've already seen. A Set implementation is helpful.

Set<String> names = new HashSet<>();
Iterator<MyType> it = getListFromSomewhere().iterator();  // you know how
while(it.hasNext()) {
   if (!names.add(it.next().getName()) {
     it.remove();
   }
}

Hint: adding to a set returns false, if the value is already in the set.

Remarks

Your requirement wasn't that clear: here we keep the first entry with a name and delete all following entries from the list. If the list is not sorted by id, then it is rather random, which entries are kept an which are removed.

score 0 · Answer 6 · answered Dec 18 '12 at 09:53

You can do it with the help of Set as well as List family

We have seen how to remove duplicates with Set family. We can do it with the help of List family as well. Please refer below code.

package com.rais.util;

import java.util.ArrayList;
import java.util.List;

/**
 * @author Rais.Alam
 * @project Utils
 * @date Dec 18, 2012
 */
public class ConverterUtil
{

    /**
     * @param args
     */
    public static void main(String[] args)
    {

        List<String> original = new ArrayList<String>();

        original.add("Tomcat");
        original.add("Jboss");
        original.add("GlassFish");
        original.add("Weblogic");
        original.add("Tomcat");

        List<String> newList = removeDuplicates(original);

        for (String value : newList)
        {
            System.out.println(value);
        }

    }

    public static List<String> removeDuplicates(List<String> original)
    {

        List<String> tempList = new ArrayList<String>();

        for (String value : original)
        {
            if (!tempList.contains(value))
            {
                tempList.add(value);
            }
        }

        return tempList;

    }

}

Avoiding printing of duplicates in ArrayList

6 Answers6