java 算法二分查找和折半查找

package com.hao.myrxjava;/** * 折半查找 ：首先数组是已经排好序的 * * @author zhanghaohao * @date 2017/5/15 */public class HalfDivision {  /**   * 循环实现   *   * @param array 排好序的数组   * @param value 查找的值   * @return value在array的位置   */  public static int halfDivision(int value, int[] array) {    if (array == null || array.length == 0)      throw new NullPointerException("array is null");    int low = 0;    int high = array.length - 1;    int mid = (low+high)/2;    while (array[mid] != value) {      if (array[mid] > value)        high = mid - 1;      else        low = mid + 1;      if (low > high)        return -1;      mid = (low+high)/2;      if (array[mid] == value)        return mid;    }    return mid;  }  /**   * 递归实现   *   * @param array 排好序的数组   * @param value 查找的值   * @param low 查找的起始位置   * @param high 查找的末尾位置   * @return value在array的位置   */  public static int halfDivision(int value, int[] array, int low, int high) {    if (low > high)      return -1;    int mid = (low + high) / 2;    if (array[mid] == value)      return mid;    else if (array[mid] > value)      return halfDivision(value, array, low, mid - 1);    else if (array[mid] < value)      return halfDivision(value, array, mid+1, high);    return -1;  }}