Java 归并排序

package cookie;

public class MergeSort {

    void mergeSort(int[] a, int[] temp, int left, int right) {
        if (left < right) {
            int center = (left + right) / 2;
            mergeSort(a, temp, left, center);
            mergeSort(a, temp, center + 1, right);
            merge(a, temp, left, center + 1, right);
        }
    }

    void merge(int[] a, int[] tempArray, int leftStart, int rightStart, int rightEnd) {
        int leftEnd = rightStart - 1;
        int tempPos = leftStart;
        int numElements = rightEnd - leftStart + 1;
        while (leftStart <= leftEnd && rightStart <= rightEnd) {
            if (a[leftStart] <= a[rightStart]) {
                tempArray[tempPos++] = a[leftStart++];
            } else {
                tempArray[tempPos++] = a[rightStart++];

            }
            while (leftStart <= leftEnd) {
                tempArray[tempPos++] = a[leftStart++];
            }
            while (rightStart <= rightEnd) {
                tempArray[tempPos++] = a[rightStart++];
            }
            for (int i = 0; i < numElements; i++, rightEnd--) {
                a[rightEnd] = tempArray[rightEnd];
            }
        }
    }
}