Java String.indexOf和空字符串 [英] Java String.indexOf and empty Strings

问题描述

我很好奇为什么 String.indexOf 在请求字符串中空字符串的索引时返回0（而不是-1）。

I'm curious why the String.indexOf is returning a 0 (instead of -1) when asking for the index of an empty string within a string.

Javadocs只说这个方法返回指定字符串的字符串中的索引，如果找不到字符串，则返回-1。

The Javadocs only say this method returns the index in this string of the specified string, -1 if the string isn't found.

对我来说，这种行为似乎非常意外，我原以为-1。任何想法为什么会发生这种意外行为？我至少认为这在方法的Javadocs中值得注意...

To me this behavior seems highly unexpected, I would have expected a -1. Any ideas why this unexpected behavior is going on? I would at the least think this is worth a note in the method's Javadocs...

System.out.println("FOO".indexOf("")); // outputs 0 wtf!!!
System.out.println("FOO".indexOf("bar")); // outputs -1 as expected
System.out.println("FOO".indexOf("F")); // outputs 0 as expected
System.out.println("".indexOf("")); // outputs 0 as expected, I think

推荐答案

空字符串无处不在，无处可去。它始终在所有的弦中，渗透着它们存在的本质，但是当你寻求它时，你永远不会瞥见它。

The empty string is everywhere, and nowhere. It is within all strings at all times, permeating the essence of their being, yet as you seek it you shall never catch a glimpse.

你能算多少空字符串在一个字符串的开头？ Mu

How many empty strings can you fit at the beginning of a string? Mu

学生对老师说，

<老师，我相信我已经找到了空字符串的本质。空的绳子就像一团灰尘，当灰尘在房间里自由漂浮，在阳光下闪闪发光时，它会自由浮动穿过绳子。

Teacher, I believe that I have found the nature of the empty string. The empty string is like a particle of dust, and it floats freely through a string as dust floats freely through the room, glistening in a beam of sunlight.

老师回应了学生，

嗯。一个好的概念。现在告诉我，灰尘在哪里，阳光在哪里？

Hmm. A fine notion. Now tell me, where is the dust, and where is the sunlight?

老师用带子敲打学生并指示他继续他的冥想。

The teacher struck the student with a strap and instructed him to continue his meditation.

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