Split String While Ignoring Escaped Character

Question

I want to split a string along spaces, ignoring spaces if they are contained inside single quotes, and ignoring single quotes if they are escaped (i.e., \' ) I have the following completed from another question.

    String s = "Some message I want to split 'but keeping this a\'s a single string' Voila!";
    for (String a : s.split(" (?=([^\']*\'[^\"]*\')*[^\']*$)")) {
        System.out.println(a);
    }

The output of the above code is

Some
message
I
want
to
split
'but
keeping
this
'a's a single string'
Voila!

However, I need single quotes to be ignored if they are escaped ( \' ), which the above does not do. Also, I need the first and last single quotes and forward slashes removed, if and only if it (the forward slashes) are escaping a single quote (to where 'this is a \'string' would become this is a 'string). I have no idea how to use regex. How would I accomplish this?

Answer 1

You need to use a negative lookbehind to take care of escaped single quotes:

String str = 
        "Some message I want to split 'but keeping this a\\'s a single string' Voila!";

String[] toks = str.split( " +(?=((.*?(?<!\\\\)'){2})*[^']*$)" );
for (String tok: toks)
    System.out.printf("<%s>%n", tok);

output:

<Some>
<message>
<I>
<want>
<to>
<split>
<'but keeping this a\'s a single string'>
<Voila!>

PS: As you noted that escaped single quote needs to be typed as \\' in String assignment otherwise it will be treated as plain '

Answer 2

or you could use this pattern to capture what you want

('(?:[^']|(?!<\\\\)')*'|\S+)  

Demo