Merge two arrays into a single sorted array using Java

Arrays are very important if you want to build a core foundation of programming. Be it any language, Arrays comes very handily in the data structure. In this article, we will share how to merge 2 different arrays into a single sorted array using Java language. We will also show the optimization being done using Java 8 Stream API library which will shorten the length of the program entirely.

Merge two arrays into a single sorted array using Java (using old versions of Java)

The code will consist of three different sections -

1. Merge two arrays
2. Remove duplicates
3. Sorting the merged array

Step 1 - Merging two different arrays

//Defining mergedArray with combined size of arrayA and arrayB

int[] mergedArray = new int[arrayA.length + arrayB.length];

//Initializing pointers of arrayA, arrayB and mergedArray with 0

int i=0, j=0, k=0;

//Inserting all elements of arrayA into mergedArray

while (i < arrayA.length)
{
 mergedArray[k] = arrayA[i];
 k++;
 i++;
}

//Inserting all elements of arrayB into mergedArray

while (j < arrayB.length)
{
 mergedArray[k] = arrayB[j];
 k++;
 j++;
}

Step 2 - Removing duplicates using HashSet

//Defining one HashSet object called setWithNoDuplicates
//Remember, HashSet allows only unique elements

Set setWithNoDuplicates = new HashSet<>();

//Adding all elements of mergedArray into setWithNoDuplicates

for (int m = 0; m < mergedArray.length; m++)
{
 setWithNoDuplicates.add(mergedArray[m]);
}

//Now, setWithNoDuplicates will have only unique elements of mergedArray

//So, now iterate setWithNoDuplicates and
//add its elements into new array called mergedArrayWithNoDuplicates

Iterator it = setWithNoDuplicates.iterator();

int[] mergedArrayWithNoDuplicates = new int[setWithNoDuplicates.size()];

int n = 0;

//Adding all elements of setWithNoDuplicates into mergedArrayWithNoDuplicates

while (it.hasNext())
{
 mergedArrayWithNoDuplicates[n] = it.next();
 n++;
}

Step 3 - Sorting

Arrays.sort(mergedArrayWithNoDuplicates);

The same can be achieved using Java 8 in few lines of code as shown below -

import java.util.Arrays;

import java.util.stream.IntStream;

 

public class MergeTwoArraysAndRemoveDuplicatesProgram 

{   

    private static int[] mergeArraysAndRemoveDuplicates(int[] arrayA, int[] arrayB)

    {

        return IntStream.concat(IntStream.of(arrayA), IntStream.of(arrayB))

                        .distinct()

                        .sorted()

                        .toArray();

    }

     

    public static void main(String[] args)

    {

        int[] arrayA = new int[] {7, -5, 3, 8, -4, 11, -19, 21};

         

        int[] arrayB = new int[] {6, 13, -7, 0, 11, -4, 3, -5};

         

        int[] mergedArray = mergeArraysAndRemoveDuplicates(arrayA, arrayB);

         

        System.out.println("Array A : "+Arrays.toString(arrayA));

         

        System.out.println("Array B : "+Arrays.toString(arrayB));

         

        System.out.println("Sorted Merged Array With No Duplicates : ");

         

        System.out.println(Arrays.toString(mergedArray));

    }

}

We will come up with more articles on Java. Happy to share. Keep learning and keep sharing!