Find all duplicate numbers in list in java



In this core java programming tutorial we will write a program to Find all duplicate numbers in list in java.


Q. Find all duplicate numbers in list in java.


Example:
list is: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 5, 10]
Duplicate numbers in list are: 5 10.




Full Program/SourceCode / Example to Find all duplicate numbers in list in java>
/** Copyright (c), AnkitMittal www.JavaMadeSoEasy.com */
import java.util.ArrayList;
import java.util.List;
public class FindDuplicatNumberInListExample {
   public static void main(String[] args) {
          List<Integer> list = new ArrayList<Integer>();     
          for (int i = 1; i <= 10; i++) {
                 list.add(i);
          }
          list.add(5);  //add duplicate number in list.
          list.add(10); //add another duplicate number in list.
          findDuplicateNumbersInList(list);
   }
   /*
   * Method prints duplicate numbers in List and returns list of non-duplicate numbers.
   */
   public static List<Integer> findDuplicateNumbersInList(List<Integer> list) {
          List<Integer> listWithoutDuplicates = new ArrayList<Integer>();
          System.out.println("list is: "+list);
          System.out.print("Duplicate numbers in list are: ");
          for (int i : list) {
                 if (listWithoutDuplicates.contains(i))
                       System.out.print(i+" ");
                 else
                       listWithoutDuplicates.add(i);
          }
          return listWithoutDuplicates;
   }
}
/*OUTPUT
list is: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 5, 10]
Duplicate numbers in list are: 5 10
*/


So in this core java programming tutorial we wrote a program how to Find all duplicate numbers in list in java.

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