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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.

Must read: Find largest of three numbers in java.

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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Labels: Core Java Level1 programs (beginners)