// merge two sorted array
    public static Integer[] merge(Integer[] arr1, Integer[] arr2){
        Integer[] array = null;
        if( arr1 != null && arr2 != null){
            int i=0, j = 0, k = 0;
            int len1 = arr1.length;
            int len2 = arr2.length;
            array = new Integer[len1+len2];
            while(k < len1 + len2) {
                if( i >= len1) {
                    array[k] = arr2[j];  // i is out of bound
                    j++;
                }
                else if( j >= len2) {
                    array[k] = arr1[i];  // j is out of bound
                    i++;
                }
                else {
                    if(arr1[i] < arr2[j]) {
                        array[k] = arr1[i];
    j                    i++;
                    }
                    else {
                        array[k] = arr2[j];
                        j++;
                    }
                }
                k++;
            }
        }
        return array;
    }

	public static Integer[] mergeSortedArr(Integer[] a1, Integer[] a2){
		int len1 = a1.length;
		int len2 = a2.length;
		Integer[] arr = new Integer[len1 + len2];
		int i = 0, j = 0, k = 0;
		while(i < len1 || j < len2){
			if(i >= len1){  
				arr[k] = a2[j];  // i is out of bound
				j++;
			}else if(j >= len2){
				arr[k] = a1[i];  // j is out of bound
				i++;
			}else{
				if(a1[i] < a2[j]){
					arr[k] = a1[i];
					i++;
				}else{
					arr[k] = a2[j];
					j++;
				}
			}
			k++;
		}
		
		return arr;
	}