二分查找比较简单，直接上代码：

    1. package com.ruoyi.search;
    3. public class BinarySearch {
    4.     public static void main(String[] args) {
    5.         int[] arr = {12, 34, 56, 67, 78, 89, 90, 122, 125, 135};
    6.         int i = binarySearch(arr, 78);
    7.         System.out.println("i = " + i);
    8.     }
    11.     /**
    12.      * 二分查找
    13.      *
    14.      * @param arr
    15.      * @param target
    16.      * @return
    17.      */
    18.     public static int binarySearch(int[] arr, int target) {
    19.         int l = 0, r = arr.length - 1, m;
    20.         while (l <= r) {
    21.             m = (l + r) >>> 1;
    22.             if (arr[m] == target) {
    23.                 return m;
    24.             } else if (arr[m] > target) {
    25.                 r = m - 1;
    26.             } else {
    27.                 l = m + 1;
    28.             }
    29.         }
    30.         return -1;
    31.     }
    32. }