public class BinarySearch
{
	public static int search(int findKey, int[] target)
	{
		int startPoint=0;
		int endPoint=target.length-1;
		while(startPoint<=endPoint)
		{
			int mid=startPoint+(endPoint-startPoint)/2;
			if(findKey<target[mid])
			{
				endPoint=mid-1;
			}
			else if(findKey>target[mid])
			{
				startPoint=mid+1;
			}
			else 
			{
				return mid;
			}
		}
		return -1;
	}
	//递归实现
	public static int rank(int findKey, int[] target)
	{
		return rank(findKey, target,0,target.length-1);
	}
	private static int rank(int findKey, int[] target, int start, int end)
	{
		//如果key存在于数组中，它的索引就不会大于end
		if(start>end)
		{
			return -1;
		}
		int mid =start+(end-start)/2;
		if(findKey<target[mid])
		{
			return rank(findKey, target,start,mid-1);
		}
		else if(findKey>target[mid])
		{
			return rank(findKey, target,mid+1,end);
		}
		else 
		{
			return mid;
		}
	}
}

测试代码：

public void testBinarySearch()
	{
		int[] target=new int[]{1,3,5,7,10};
		System.out.println(BinarySearch.rank(10, target));
		System.out.println(BinarySearch.search(10, target));
	}

迭代可以实现的尾递归都可以实现！