What is Merge Sort In Java? Algorithms Explained

Do you know what is ‘Merge Sort in Java Programming’? Java is a quite vast programming language and you will learn so many concepts while studying your Java course. Merge Sort is an important concept and let us try to understand what is Merge sort in Java using the recursion method along with some examples. Still, if you have any questions related to merge sort or any issues while solving your Java assignment then you can get Java Assignment help by hiring the proficient experts at CodingZap. But before we start implementing the Merge Sort example in this article, let us have a look at the definition of the Merge Sort process in computer science. We should clear a basic understanding of the Merge Sort algorithm process.  

What Is Merge Sort In Java Programming Language? Read Below

  In computer science, there are a lot of sorting algorithms present. The sorting algorithms are used to sort the elements in any specific order. Generally, the elements are sorted in an ascending manner. In every sorting algorithm, the elements are provided in some data structure format. But most of the time, the elements are provided using the array concept. We should sort the elements in the array using different sorting algorithms. There are mainly nine sorting algorithms present. Like, Quick Sort Algorithm, Bubble Sort Algorithm, Insertion Sort Algorithm, Heap Sort Algorithm & many more. Among them, Merge Sort is one type of sorting algorithm. But you might ask why there is a need to have so many sorting algorithms. We need such many sorting algorithms because; every sorting algorithm works on different datasets. If these sorting algorithms are used for any particular dataset, then the time consumption will be different for each other. And the main intention of Algorithms is to take less time to compile any process. That is the reason; developers get different sorting algorithm options to use in their code to achieve minimum time complexity. Along with the time complexity, the space complexity also matters in this case. For all of these reasons, several sorting algorithms are present. The merger sort algorithm completely depends upon the process where a large dataset is divided into small parts. The merge sort algorithm reduces a large dataset or array into small pieces. Here, each element in the array is considered as a small piece. Based on the pieces, the merge sort algorithm gets the result. It compares all the elements one by one & then makes the resultant array by combing all the elements again. In this way, the whole merge sort algorithm process is executed. Now, are you getting any pattern from the working principle of the Merge sort algorithm? Do you know what this pattern is called in computer science? The pattern where a large dataset is divided into small parts & the result is being calculated on them. And for generating the final result, if the small data elements are again merged, the process is known as the Divide & Conquer technique. The Merge sort algorithm follows the Divide & Conquer technique for getting the result data. Divide stands for the breaking of the large dataset. And Conquer stands for the merging of the small dataset again after doing the necessary operations. The merge sort algorithm is associated with the C programming language. The first implementation was done with the help of the C programming language only. But nowadays, such important programming language needs to be implemented in either Java or Python programming language. We all know about the process to implement Quicksort in Python Programming Language. Now, after discussing the basic of the Merge sort algorithm. Let us know the steps needed for the development of Merge Sort in Java Programming Language. Also, if you want to know about methods to reverse a list in Java then you learn more about reverse a list in Java.  

What Are The Steps Required For Merge Sort In Java Programming Language? Get To Know

  Now, after clearing the basic of the Merge sort algorithm, we should discuss the steps that are involved in the implementation process. Here, we will discuss the steps with one sample dataset. We should focus on the images below with the steps mentioned here. As we all know, in the Merge sort algorithm process, there are three steps involved. They are Dividing, Sorting & Conquer. We will all know about these steps one by one along with the example. Suppose, one dataset has been collected in the form of an array. There are four elements present in an unsorted manner. The dataset is like 2,1,4,3. Now, we will use the Merge sort algorithm on it. Let us check the following steps.

• Divide Step:

In this step, the large dataset is divided into small parts. For that purpose, we should find out the middle element in the set. If there are an odd number of elements are present, then finding the middle element is easy. But in the case of an even number of elements, the middle element is not present there.  Here, four elements are present. So, no middle elements can be derived from the list. But we can easily divide the array into two parts. In that case, two new sub-arrays are formed. They are 2,1 & 4,3.  If there is a presence of the middle element it will belong to any of the substrings. Hence, the substrings will have unequal lengths. But in this case, such unequal length of substring is not present. Hence, the divide step is now completed. We can move to the next step.

• Sorting Step:

In this step, the sorting of the elements will be done. But in some cases, the algorithm performs in a way that divides the element more. In this example, the sub-arrays have only two elements each. That is also low in several terms.  But some algorithms divide it further into small parts & make substrings with only one element. It completely depends upon the programmer’s choice. Here, we will move with the sub-array where only two elements are present. Now, as the step suggests, we need to sort the elements into ascending order. We can do the swapping of the elements for that purpose. Now, the subarrays will be modified & new subarrays are 1,2 & 3,4. So, the sorting has been completely done there.

• Conquer Step:

Now, it is time to merge all the sub-arrays into the final array. For that purpose, we can declare another large result array in the program. Else, we might use one of the sub-arrays & paste the elements of other sub-arrays as it is to the first one. The second approach is better for the program. Because, if the result large array has declared, it will consume more space in the program. That will reduce the acceptance of the program. As a programmer, you should pay attention to your code’s time & space complexity. Hence, the complete process has been done.  

What Is The Pseudo-Code For Merge Sort Process In Java Programming Language?

  We hope that the steps involved in the merge sort algorithm process are now clear to you. So, we can move ahead with the implementation of the merge sort algorithm in the Java programming language. But before that, we should have a look at the Pseudo-code of the process. Though we have discussed the steps required in the merge sort algorithm process in a good manner, still the necessity of the Pseudo code is there. Because the Pseudo-code is going to give the programming vibe in your mind regarding the Merge sort algorithm. Pseudo-codes are the blueprint for the programming implementation process. The Pseudo-codes are implemented using the simple language which will help to understand the workflow. So, let us have a look at the following Pseudo-code.

Function-Mergesort(array, first element, last element)

get middle = (first + last)/2

call again Function-Mergesort(array, first element, middle)

call again Function-Mergesort(array, middle, last element)

combine both results & print

  We will follow the above Pseudo-code for the development process of the Merge sort algorithm in the Java programming language. So, let us start our core & important discussion in this article.  

How To Implement The Merge Sort Algorithm In Java Programming Language?

  To implement merge sort in the Java programming language, we should import some necessary packages to the program. Here, we will first import the Java utility package into the program. After importing that, we will move to the main function development. Inside the main function, the unsorted data will be assigned. And the function will be called where the complete operation will be executed. While calling the function, we should share the array along with its first & last index number. The first index number will be zero & the last index will be the end length of the array. In that faction, the terminating condition will be developed. The terminating condition will check the left element & the right element of the array. If they are the same, then the program will be terminated. In other cases, the program will find out the middle of the array. Based upon that middle element, the left & right sub-arrays will be formed. And those sub-arrays will be called using the recursion function. For calling the recursion function, we should follow some conditions. The left sub-array will stretch from the beginning index to the middle index number. So, while recursively calling the function, you need to change the index number. For the right sub-array, the same method will be followed, but with a different index number. The right sub-arrays will stretch from the next middle element to the last index number. So, for calling that recursive function, you need to be cautious. After getting all the data & the sub-arrays become sorted, the combination of the work will be done. For that purpose, one separate function is being declared. In a separate array, the sub-array data are stored. For that purpose, we have used some while loops. Also, if you want to learn about How to print an array in Java then you can also read our blogs. In the end, the data needs to be printed. That is the reason, one separate function is declared in the program. It will use the result array & provide the output in the program. Hence, we have successfully implemented the merge sort algorithm in Java programming language.  

Example:

 

import java.util.*;

public class Main {public static int[] merge(int[] a, int f, int l) {if(f == l) { //Base Case To Terminate The Recursion Function

int [] r = new int[1];r[0]= a[f]; return r;}int m = (f + l)/2; // Getting The Middle Part Of The Array

int [] ls = merge(a,f,m); // Recursion Calling For The Left Subarray

int[] rs = merge(a,m+1,l); // Recursion Calling For The Right Subarray

int [] an = result(ls,rs); // Calling Function For Getting The Final Array Result

return an; }

  public static int[] result(int[] x1, int[] x2){  int a1 = 0, a2 =0, a3 = 0; int[] x3 = new int[x1.length + x2.length]; // Creation Of Array Which Contains Merged Sorted Elements

    while(a1 < x1.length && a2 < x2.length){ // Implementation Of While Loop For Merging

        if(x1[a1] <= x2[a2]){x3[a3] = x1[a1];a1++; a3++;}else{ x3[a3] = x2[a2];a2++;a3++;}}

    while(a1 < x1.length){ // Implementation Of While loop For First Part

      x3[a3] = x1[a1];a3++;a1++; }

    while(a2 < x2.length){ // Implementation Of While loop For Second Part

      x3[a3] = x2[a2]; a3++;a2++; } return x3;}

  public static void data(int[] x) { // Function For Printing The Array

    for (int i = 0; i < x.length; i++) {System.out.print(x[i] + " "); }System.out.println();}

  public static void main(String[] args)  {int[] a = {2,1,4,3}; // Assigning The Unsorted Array Value 

    System.out.print("Original Array: ");data(a);

    int[] b = merge(a,0,a.length - 1); // Calling The Function For Merge Sorting

    System.out.print("Sorted Array: "); data(b); }

  Let us try to find out the output of the above code. It will help to understand the implementation process of merge sort in the Java programming language.  

Output:

   

Conclusion:

  As we saw Merge sort in Java programming language is a very important topic to know. The implementation process of the merge sort algorithm depends upon the use of an array in the program. Still having issues understanding, you can always hire a programming tutor from CodingZap to clear your all doubts. So, the Data Structure concept along with the Algorithm part needs to be cleared before moving to the implementation process. It is also advisable to clear some basic concepts in the Java programming language.  There are some complex elements are used in this program to implement the merge sort algorithm. You should first have a nice grip on the preliminary idea of Java programming language. Then the implementation will become a cakewalk for you. Also, if you are a Final year student then you must be looking for Java project ideas.