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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).

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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<Integer> list = new ArrayList<Integer>();

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<Integer> 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.

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Labels: Core Java Level1 programs (beginners)