二分查找

二分查找数组必须为有序数组，查找速度比无序数组快，插入速度比无序数组慢。
查找次数为数组长度的开方。
方法：
public static int find(long searchKey) {
long[] arr = new long[100];
arr[0] = 11;
arr[1] = 22;
arr[2] = 33;
arr[3] = 44;
arr[4] = 55;
arr[5] = 66;
arr[6] = 77;
arr[7] = 88;
arr[8] = 99;
arr[9] = 100;

int countElems = 10;
int lowerElem = 0;
int upperElem = countElems - 1;
int currIn;
while (true) {
currIn = (lowerElem + upperElem) / 2;
if (arr[currIn] == searchKey) {
return currIn;
} else if (lowerElem > upperElem) {
return countElems;
} else {
if (arr[currIn] < searchKey) {
lowerElem = currIn + 1;
} else {
upperElem = currIn - 1;
}
}
}
}

调用：
public static void main(String[] args) {

long a = find(111);
System.out.println(a);

}