执行此split（）函数时为什么java与javascript不同

Question

In javascript

",,".split(",").length   // Return 3

But in java:

",,".split(",").length   // Return 0

Why java ignores all empty string in between when split string with charater?

Answer 1

Java are having two overloading functions of String.split(..)

 1. public String[] split(String regex, int limit){}
 2. public String[] split(String regex) . This equals with split(String regex, int limit = 0)

With limit parameter make String.spit of java flexible. The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. If the limit n is greater than zero then the pattern will be applied at most n - 1 times, the array's length will be no greater than n, and the array's last entry will contain all input beyond the last matched delimiter. If n is non-positive then the pattern will be applied as many times as possible and the array can have any length. If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded. More detail here

So in your case with java:

",,".split(",").length   // Return 0
",,".split(",", -1).length   // Return 3

Answer 2

To know why there is difference you will have to understand split(String regex, int limit) first.

The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. And they specifically says

If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded.

java docs

Now in split(String regex) . This overloaded function is supposed to give the same result as above with a limit argument of zero.

This method works as if by invoking the two-argument split method with the given expression and a limit argument of zero. Trailing empty strings are therefore not included in the resulting array.

Now on the other hand when we talk about javascript. We know there could not be any overloading in it. They made a single function and have optional parameter. If you provide limit argument it will limit on the number of splits to be found.

Integer specifying a limit on the number of splits to be found. The split() method still splits on every match of separator, until the number of split items match the limit or the string falls short of separator.

javascript docs from developer.mozilla.org