Merge-Sort Algorithm implementation in JAVA

Merge-Sort Function

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void MergeSort(int low, int high)    // a[low : high] is a global array to be sorted.    // Small(P) is true if there is only one element to    // sort. In this case the list is already sorted.    {        if (low < high) { // If there are more than one element               // Divide P into subproblems.               // Find where to split the set.               int mid = (low + high)/2;               // Solve the subproblems.               MergeSort(low, mid);               MergeSort(mid + 1, high);               // Combine the solutions.               Merge(low, mid, high);        }    }      void Merge(int low, int mid, int high)    // a[low:high] is a global array containing two sorted    // subsets in a[low:mid] and in a[mid+1:high]. The goal    // is to merge these two sets into a single set residing    // in a[low:high]. b[] is an auxiliary global array.    {        int h = low, i = low, j = mid+1, k;        while ((h <= mid) && (j <= high)) {           if (a[h] <= a[j]) { b[i] = a[h]; h++; }           else { b[i] = a[j]; j++; } i++;        }        if (h > mid) for (k=j; k<=high; k++) {                        b[i] = a[k]; i++;                     }        else for (k=h; k<=mid; k++) {                b[i] = a[k]; i++;             }        for (k=low; k<=high; k++) a[k] = b[k];    }

Merge Sort Java Code :

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import java.util.*;   public class MergeSort {  public int a[] = new int[50];    public void merge_sort(int low, int high) {   int mid;   if (low < high) {    mid = (low + high) / 2;    merge_sort(low, mid);    merge_sort(mid + 1, high);    merge(low, mid, high);   }  }    public void merge(int low, int mid, int high) {   int h, i, j, k;   int b[] = new int[50];   h = low;   i = low;   j = mid + 1;     while ((h <= mid) && (j <= high)) {    if (a[h] <= a[j]) {     b[i] = a[h];     h++;    } else {     b[i] = a[j];     j++;    }    i++;   }   if (h > mid) {    for (k = j; k <= high; k++) {     b[i] = a[k];     i++;    }   } else {    for (k = h; k <= mid; k++) {     b[i] = a[k];     i++;    }   }   for (k = low; k <= high; k++)    a[k] = b[k];  }    public MergeSort() {   int num, i;     System.out.println("             MERGE SORT PROGRAM            ");     System.out.println();   System.out.println();   System.out     .println("Please Enter THE No. OF ELEMENTS you want to sort[THEN PRESS ENTER]:");   num = new Scanner(System.in).nextInt();   System.out.println();   System.out.println("Now, Please Enter the (" + num     + ") nos. [THEN PRESS ENTER]:");   for (i = 1; i <= num; i++) {    a[i] = new Scanner(System.in).nextInt();   }   merge_sort(1, num);   System.out.println();   System.out.println("So, the sorted list (using MERGE SORT) will be :");   System.out.println();   System.out.println();     for (i = 1; i <= num; i++)    System.out.print(a[i] + "    ");    }    public static void main(String[] args) {   new MergeSort();  } }