java - 数组搜索方法困惑

Question

我对 Arrays.binarySearch(Object[], Object) 感到困惑.

public class SearchObjArray {

    public  static void main(String[] args){

        String[] sa = {"one","two","three","four"};

        Arrays.sort(sa);

        for(String s : sa ){
            System.out.println(s + " ");
        }
        System.out.println("\n one = " + Arrays.binarySearch(sa,"thro"));
}
}

当程序运行时，它返回位置-4。我在书中读到，它指出，插入点表示为 (-(insertionPoint)-1)。为什么会这样呢？我无法理解这一点。

Answer 1

The insertion point is defined as the point at which the key would be inserted into the array.

{"one","two","three","four"}

排序后为

{"four", "one", "three", "two"}

和throw位于三之后。所以插入点是3。结果是

(-(insertionPoint) -1) =
(-(3)              -1) =
-4