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Remove duplicate elements in Java with HashSet
Set implementations in Java has only unique elements. Therefore, it can be used to remove duplicate elements.
Let us declare a list and add elements −
List < Integer > list1 = new ArrayList < Integer > (); list1.add(100); list1.add(200); list1.add(300); list1.add(400); list1.add(400); list1.add(500); list1.add(600); list1.add(600); list1.add(700); list1.add(400); list1.add(500);
Now, use the HashSet implementation and convert the list to HashSet to remove duplicates −
HashSet<Integer>set = new HashSet<Integer>(list1); List<Integer>list2 = new ArrayList<Integer>(set);
Above, the list2 will now have only unique elements.
Example
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
public class Demo {
public static void main(String[] argv) {
List<Integer>list1 = new ArrayList<Integer>();
list1.add(100);
list1.add(200);
list1.add(300);
list1.add(400);
list1.add(400);
list1.add(500);
list1.add(600);
list1.add(600);
list1.add(700);
list1.add(400);
list1.add(500);
HashSet<Integer>set = new HashSet<Integer>(list1);
List<Integer>list2 = new ArrayList<Integer>(set);
System.out.println("List after removing duplicate elements:");
for (Object ob: list2)
System.out.println(ob);
}
}Output
List after removing duplicate elements: 400 100 500 200 600 300 700
Updated on: 30-Jul-2019
9K+ Views
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