为何“超出范围”没有为'substring（startIndex，endIndex）'抛出

问题描述

在Java中我使用的是 substring（）方法，我不确定为什么它没有抛出out of index错误。

In Java I am using the substring() method and I'm not sure why it is not throwing an "out of index" error.

字符串 abcde 索引从0开始到4，但 substring（）方法将startIndex和endIndex作为参数，基于我可以调用foo.substring（0）并获取abcde这一事实。

The string abcde has index start from 0 to 4, but the substring() method takes startIndex and endIndex as arguments based on the fact that I can call foo.substring(0) and get "abcde".

那么为什么子串（5）工作？该指数应该超出范围。解释是什么？

Then why does substring(5) work? That index should be out of range. What is the explanation?

/*
1234
abcde
*/
String foo = "abcde";
System.out.println(foo.substring(0));
System.out.println(foo.substring(1));
System.out.println(foo.substring(2));
System.out.println(foo.substring(3));
System.out.println(foo.substring(4));
System.out.println(foo.substring(5));

此代码输出：

abcde
bcde
cde
de
e
     //foo.substring(5) output nothing here, isn't this out of range?

当我用6替换5时：

foo.substring(6)

然后我收到错误：

Exception in thread "main" java.lang.StringIndexOutOfBoundsException:
    String index out of range: -1

推荐答案

根据，substring在启动索引时抛出错误大于字符串的 Length 。

According to the Java API doc, substring throws an error when the start index is greater than the Length of the String.

事实上，他们举了一个像你的例子：

In fact, they give an example much like yours:

"emptiness".substring(9) returns "" (an empty string)

我想这意味着最好考虑一个Java String如下所示，其中索引包含在 | 中：

I guess this means it is best to think of a Java String as the following, where an index is wrapped in |:

|0| A |1| B |2| C |3| D |4| E |5|

这就是说字符串同时包含起始和结束索引。

Which is to say a string has both a start and end index.

这篇关于为何“超出范围”没有为'substring（startIndex，endIndex）'抛出的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！