public static int getindex(int[] arr,int find) {
		int min = 0;
		int max = arr.length - 1;
		int mid = (min + max) / 2;
		
		while(find != arr[mid]) {
			if(find < arr[mid]) {
				max = mid -1;
			}else {
				min = mid +1;
			}
			mid = (min + max) /2;
			if(min > max) {
				return -1;
			}
		}
		return mid;
	}

核心思想：取中间的索引来进行查找

优点：平均查找性能比较好

缺点：查找的数组必须是有顺序