二分查找的必要条件是必须有序的数列
public static int binarySearch(int[] array,int key){
int left = 0;
int right = array.length-1;
while(left <= right){
int mid = (left+right)/2;
if(array[mid] > key){
right = mid - 1;
}else if(array[mid] < key){
left = left + 1;
}else{
return mid;
}
}
return -1;
}
public static void main(String[] args) {
int[] array = {12,14,15,16,18,23};
System.out.println(binarySearch(array, 15));
}打印结果：
