java算法之折半查找

package althorgrim;
/**
 * 1、必须采用顺序存储结果
 * 2、关键字必须有序
 * @author hanrk-2734
 *
 */
public class TestBinarySearch {
	
	
	public static int binarySearch(int a[],int goal){
		int high=a.length-1;
		int low=0;
		while (low<=high) {
			int middle=(low+high)/2;
			if (a[middle]==goal) {
				return middle;
			}
			else if (a[middle]>goal) {
				high=middle-1;
			}
			else {
				low=middle+1;
			}
		}
		return -1;
	
		
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int[] src = new int[] {1, 3, 5, 7, 8, 9};
		System.out.println(binarySearch(src, 3)); 
	}

}