java基础之二分法查找

package p;
public class NumberSearch {
 /**
	 * @param args
	 *    二分查找法
	 */
	public static void main(String[] args) {
		int[] arr = new int[] { 12, 23, 34, 45, 56, 67, 77, 89, 90 };
		System.out.println(NumberSearch.NumSearch(arr, 12));
		System.out.println(NumSearch(arr, 45));
		System.out.println(NumSearch(arr, 67));
		System.out.println(NumSearch(arr, 89));
		System.out.println(NumSearch(arr, 99));
	}
	public static int NumSearch(int arr[], int key) {
		int start = 0;
		int end = arr.length - 1;
		while (start <= end) {
			int middle = (start + end) / 2;
			if (key < arr[middle]) {
				end = middle - 1;
			} else if (key > arr[middle]) {
				start = middle + 1;
			} else {
				return middle;
			}
		}
		return -1;
	}
}