二进制搜索java数组。binarySearch无法找到目标

Question

String[] sortedArray = new String[]{"Quality", "Name", "Testing", "Package"};   

// Search for the word "cat" 
int index = Arrays.binarySearch(sortedArray, "Quality");  

我总是得到-3。问题出在"Name"。为什么我的数组中不能有"Name"？有什么想法吗

Answer 1

必须对数组进行排序，才能进行二进制搜索。{a1}的javadoc说：

The array must be sorted into ascending order according to the natural ordering of its elements (as by the sort(Object[]) method) prior to making this call. If it is not sorted, the results are undefined.

（重点加上。）

原因很简单。二进制搜索算法的前提是输入数组已排序

Answer 2

要使用binarySearch，首先需要自己对数组进行排序：

String[] sortedArray = new String[]{"Quality", "Name", "Testing", "Package"};   

java.util.Arrays.sort(sortedArray);

int index = Arrays.binarySearch(sortedArray, "Quality");  

Answer 3

必须对数组进行排序。从binarySearch（）的Javadoc：

The range must be sorted into ascending order according to the natural ordering of its elements prior to making this call. If it is not sorted, the results are undefined.