MergeSort gives StackOverflow error - algorithm

Question

this is the code for the mergeSort,this gives an stackoverflow error in line 53 and 54(mergeSort(l,m); and mergeSort(m,h);)
Any help will be regarded so valuable,please help me out,i am clueless,Thank you.
package codejam;
public class vector {
static int[] a;
static int[] b;
public static void main(String[] args) {
int[] a1 = {12,33,2,1};
int[] b1 = {12,333,11,1};
mergeSort(0,a1.length);
a1=b1;
mergeSort(0,b1.length);
for (int i = 0; i < a1.length; i++) {
System.out.println(a[i]);
}
}
public static void merge(int l,int m,int h) {
int n1=m-l+1;
int n2 = h-m+1;
int[] left = new int[n1];
int[] right = new int[n2];
int k=l;
for (int i = 0; i < n1 ; i++) {
left[i] = a[k];
k++;
}
for (int i = 0; i < n2; i++) {
right[i] = a[k];
k++;
}
left[n1] = 100000000;
right[n1] = 10000000;
int i=0,j=0;
for ( k =l ; k < h; k++) {
if(left[i]>=right[j])
{
a[k] = right[j];
j++;
}
else
{
a[k] = left[i];
i++;
}
}
}
public static void mergeSort(int l,int h) {
int m =(l+h)/2;
if(l<h)
{
mergeSort(l,m);
mergeSort(m,h);
merge(l,m,h);;
}
}
}

Answer 1

Following is the recursive iterations table of the mergeSort function with argument l=0 and h=4
when the value of l is 0 and value of h is 1 , expression calculate m value which turn out to be 0 but we are checking condition with h which is still 1 so 0<1 become true , recursive calls of this mergeSort function forms a pattern , this pattern doesn't let the function to terminate , stack runs out of memory , cause stackoverflow error.

Answer 2

import java.lang.*;
import java.util.Random;
public class MergeSort {
public static int[] merge_sort(int[] arr, int low, int high ) {
if (low < high) {
int middle = low + (high-low)/2;
merge_sort(arr,low, middle);
merge_sort(arr,middle+1, high);
arr = merge (arr,low,middle, high);
}
return arr;
}
public static int[] merge(int[] arr, int low, int middle, int high) {
int[] helper = new int[arr.length];
for (int i = 0; i <=high; i++){
helper[i] = arr[i];
}
int i = low;
int j = middle+1;
int k = low;
while ( i <= middle && j <= high) {
if (helper[i] <= helper[j]) {
arr[k++] = helper[i++];
} else {
arr[k++] = helper[j++];
}
}
while ( i <= middle){
arr[k++] = helper[i++];
}
while ( j <= high){
arr[k++] = helper[j++];
}
return arr;
}
public static void printArray(int[] B) {
for (int i = 0; i < B.length ; i++) {
System.out.print(B[i] + " ");
}
System.out.println("");
}
public static int[] populateA(int[] B) {
for (int i = 0; i < B.length; i++) {
Random rand = new Random();
B[i] = rand.nextInt(20);
}
return B;
}
public static void main(String[] args) {
// TODO Auto-generated method stub
int A[] = new int[10];
A = populateA(A);
System.out.println("Before sorting");
printArray(A);
A = merge_sort(A,0, A.length -1);
System.out.println("Sorted Array");
printArray(A);
}
}