二分搜索的java源码实践

平常编程中，经常要用到二分搜索。

java JDK中的java.lang.Arrays类中已经实现了二分搜索。

可以方便地在一个已排序好数组中，查找给定的元素。

数组元素可以是byte，int，char，long，float，double等等基本类型。

今天我自己用java实现一次，分别用递归和非递归两种方式实现。java源码如下：

//非递归实现public static String binarySearch2(int[] array, int value) {String result = "index of " + value + " is ";int low = 0;int high = array.length - 1;int middle = 0;while (low <= high) {middle = (low + high)>>1;if (array[middle] == value) {return result + middle;} else if (array[middle] < value) {low = middle + 1;} else {high = middle - 1;}}return "no such element" + value;}//递归实现public static String binarySearchRecursive(int[] array, int start, int end, int value) {String result = "index of " + value + " is ";if (start <= end) {int middle = (start + end)>>1;if (array[middle] == value) {result += middle;System.out.println(result);return result;} else if (array[middle] < value) {return binarySearchRecursive(array, middle + 1, end, value);} else {return binarySearchRecursive(array, start, middle - 1, value);}}return "no such element " + value;}public static void main(String[] args) {int[] array = {1,2,3,4,5,6,7,8,9};String result = binarySearchRecursive(array, 0, array.length - 1, 3);System.out.println(result);}

递归实现的结果如下：（注意递归函数与非递归函数的区别）

index of 3 is 2
index of 3 is 2

非递归实现如下：

index of 3 is 2