Error when using Java String split

Question

HI All,

I've been using the basic split for a while - where I just parse out a string into an array based on a simple token like " " or ",".

So of course a customer tries this: \\.br\ which fails miserably.

I need to parse to an array of lines. The string for example looks like this:

"LINE 1\\.br\\LINE 2\\.br\\LINE 3\\.br\\LINE 4\\.br\\"

and this fails with java.util.regex.PatternSyntaxException: Unexpected internal error.

Any ideas?

show us the code you are failing. also you still can use indexOf("\\.br\\") and loop over it — Pyrolistical
– Pyrolistical, Commented Mar 31, 2010 at 23:07

axtavt · Accepted Answer · 2010-03-31 23:19:39Z

5

You can use Pattern.quote() to escape a string for using as regexp:

... = s.split(Pattern.quote("\\.br\\"));

edited Mar 31, 2010 at 23:19

answered Mar 31, 2010 at 23:09

axtavt

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4 Comments

newacct Over a year ago

this requires Java 5 by the way

Donal Fellows Over a year ago

So does using regexp-based splitting anyway, IIRC.

Alan Moore Over a year ago

@Donal: Regex support, including split(), has been around since JDK 1.4. quote() was added in JDK 1.5.

Donal Fellows Over a year ago

@Alan: OK, so I was wrong. (I'm working with webservices mostly, and have for quite a while now; they tend to force 1.6 as a minimum.)

jayshao · Accepted Answer · 2010-04-02 20:53:33Z

2

Don't forget String.split takes a Regex, and most people put in a string literal, so you have to escape the \ for regex and escape it for strings, so you end up with "\\\" in your String argument to represent a single \ character.

e.g.

String.split("\\\")

so in your case:

String.split("\\\\\\.br\\\\") // extra slash for regex, and String encoded

edited Apr 2, 2010 at 20:53

answered Mar 31, 2010 at 23:09

jayshao

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6 Comments

Stephen C Over a year ago

-1 - you need four slashes, not three. Three slashes will give you a Java compilation error.

Ha. Over a year ago

Actually, he need 5 slashes at the beginning because "." should be escaped too.

Alan Moore Over a year ago

Actually, to match a backslash followed by a dot you need six backslashes: four to match the backslash and two to escape the dot.

jayshao Over a year ago

Good point - that's what I get for typing w/o the computer in front of me - updating - should only be 5 though, not 6, since the String above is also escaped in the literal.

Alan Moore Over a year ago

No, it has to be six: "\\\\" to match the backslash and "\\." to match the dot. And another four at the end to match the trailing backslash. The way you've got it now--five before and three after--won't even compile.

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