java排序算法-归并排序

public class MergeSort {

	private static void mergeSortTest() {
		int[] in = { 2, 5, 3, 8, 6, 7, 1, 4, 0, 9 };
		Utils.printArray("归并排序前：",in);
		int a[] = mergeSort(in);
		Utils.printArray("归并排序后：",a);
	}

	private static int[] mergeSort(int[] arr) {
		if (arr.length == 1) {
			return arr;
		} else {
			int[] arrL = new int[arr.length / 2];
			int[] arrR = new int[arr.length - arr.length / 2];
			int mid = arr.length / 2;
			for (int i = 0; i < mid; i++) {
				arrL[i] = arr[i];
			}
			for (int i = mid, j = 0; i < arr.length; i++, j++) {
				arrR[j] = arr[i];
			}
			int[] sortedArrL = mergeSort(arrL);
			int[] sortedArrR = mergeSort(arrR);
			int[] resultArr = mergeTwoArr(sortedArrL, sortedArrR);
			return resultArr;
		}
	}

	private static int[] mergeTwoArr(int[] arrL, int[] arrR) {
		int i = 0, j = 0;
		int[] arrTmp = new int[arrL.length + arrR.length];
		int foot = 0;
		while (i < arrL.length && j < arrR.length) {
			if (arrL[i] <= arrR[j]) {
				arrTmp[foot++] = arrL[i++];
			} else {
				arrTmp[foot++] = arrR[j++];
			}
		}
		if (i == arrL.length) {
			while (j < arrR.length) {
				arrTmp[foot++] = arrR[j++];
			}
		} else {
			while (i < arrL.length) {
				arrTmp[foot++] = arrL[i++];
			}
		}
		return arrTmp;
	}

	public static void main(String[] args) {
		mergeSortTest();
	}
}