how to write a merge sort array method ni java

1public static void mergeSort(int[] a, int n) {
2    if (n < 2) {
3        return;
4    }
5    int mid = n / 2;
6    int[] l = new int[mid];
7    int[] r = new int[n - mid];
8 
9    for (int i = 0; i < mid; i++) {
10        l[i] = a[i];
11    }
12    for (int i = mid; i < n; i++) {
13        r[i - mid] = a[i];
14    }
15    mergeSort(l, mid);
16    mergeSort(r, n - mid);
17 
18    merge(a, l, r, mid, n - mid);
19}
20

1public static void merge(
2  int[] a, int[] l, int[] r, int left, int right) {
3  
4    int i = 0, j = 0, k = 0;
5    while (i < left && j < right) {
6        if (l[i] <= r[j]) {
7            a[k++] = l[i++];
8        }
9        else {
10            a[k++] = r[j++];
11        }
12    }
13    while (i < left) {
14        a[k++] = l[i++];
15    }
16    while (j < right) {
17        a[k++] = r[j++];
18    }
19}
20