Find only duplicate number in given list in java

In this core java programming tutorial we will write a program to Find only duplicate number in given list in java.

Hi! In this post we will write a program to find out only duplicate number in given list in java.

We are given a list from 1 to 10(where series go from 1 to 10), with one added duplicate number in list.
Note: in below program as program suggests there must not be more than 1 duplicate number,
in below program we could change 10 to any other number as well.

Example>
Let’s say series given to us is : 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 5
We got to figure out 5 (as it is duplicate).

Full Program/SourceCode / Example to Find only duplicate number in given list in java >
 /** Copyright (c), AnkitMittal www.JavaMadeSoEasy.com */ import java.util.ArrayList; import java.util.List; public class FindOnlyDuplicateNumberInListExample {       public static void main(String...a){        List list = new ArrayList();        int highestNumberInList=10;   //you may change it in future.        for(int i=1;i<=highestNumberInList;i++){            list.add(i);        }        list.add(5); //add duplicate number in list(please ensure you don't add more than one duplicate number in list)        System.out.println("list is: "+list);        System.out.println("Only duplicate number in list is: "+findOnlyDuplicateNumberInList(list,highestNumberInList));    }    /**    * returns only duplicate number in list.    */    public static int findOnlyDuplicateNumberInList(List list, int highestNumberInList){             int sumOfNumbersList = 0;        for(int n:list){           sumOfNumbersList =sumOfNumbersList+n;        }               int onlyDuplicateNumberInList = sumOfNumbersList - ((highestNumberInList)*(highestNumberInList+1)/2);        return onlyDuplicateNumberInList;    } } /*OUTPUT list is: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 5] Only duplicate number in list is: 5 */

So in this core java programming tutorial we wrote a program to Find only duplicate number in given list in java.

Having any doubt? or you you liked the tutorial! Please comment in below section.