二分查找

	public static void main(String[] args) {
		int[] num = {6,5,9,8,45,2,3,55,1};
		Arrays.sort(num);//升序排序
		
		int left = 0;//左边开始
		int right = num.length;//右边开始
		int key = 55;//要查找的
		int middle = 0;//中间值
		while(true){
			middle = (left+right)/2;
			if(key==num[middle]){
				break;
			}else if(key>num[middle]){
				left = middle+1;
			}else if(key<num[middle]){
				right = middle-1;
			}
		}
		
		System.out.println(middle);//排序后key的下标
	}