How do I split a string using a regular expression that excludes an escaped version of my token?

Question

In Java, I'm using the String split method to split a string containing values separated by semicolons.

Currently, I have the following line that works in 99% of all cases.

String[] fields = optionsTxt.split(";");

However, the requirement has been added to include escaped semicolons as part of the string. So, the following strings should parse out to the following values:

"Foo foo;Bar bar" => [Foo foo] [Bar bar]
"Foo foo\; foo foo;Bar bar bar" => [Foo foo\; foo foo] [Bar bar bar]

This should be painfully simple, but I'm totally unsure about how to go about it. I just want to not tokenize when there is a \; and only tokenize when there is a ;.

Does anyone out there know the magic formula?

Answer 1

There's probably a better way but the quick-and-dirty method would be to first replace \; with some string that won't appear in your input buffers, like {{ESCAPED_SEMICOLON}}, then do the tokenize on ;, and then when you pull out each token do the original substitution in reverse to put back the \;

Answer 2

try this:

String[] fields = optionsTxt.split("(?<!\\\\);");

Answer 3

Using a regular expression (java.util.regex)

[^\\];

should be what you are looking for without doing a double replace.

try it out using a tool like this

Answer 4

Using only your provided examples, you can use objects' code from above. If you want the split to happen only when there's an even number of backslashes before your semi-colon, try this:

String[] fields = optionsTxt.split("((?<!\\\\)|(?<=[^\\\\](\\\\\\\\){0,15}));");

I've picked 15 arbitrarily. Change it to a higher number if need be.