Regex in java for the string

Question

I am very new programmer to Java regular expressions. I do not want to use java split with delimiters and try getting the individual tokens. I don't feel its a neat way. I have the following string

"Some String lang:c,cpp,java file:build.java"

I want to break up this into three parts

1 part containing "Some String" 
2 part containing "c,cpp,java" 
3 String containing "build.java"

The lang: and file: can be placed any where and they are optional.

Why not split? It's certainly not bad.

adarshr
– adarshr

2011-04-18 12:43:49 +00:00
Commented Apr 18, 2011 at 12:43 — adarshr
– adarshr, Commented Apr 18, 2011 at 12:43
Well I feel split makes it more difficult to maintain

Nandish A
– Nandish A

2011-04-18 12:45:54 +00:00
Commented Apr 18, 2011 at 12:45 — Nandish A
– Nandish A, Commented Apr 18, 2011 at 12:45

Thomas · Accepted Answer · 2011-04-18 12:49:44Z

1

The lang: and file: can be placed any where and they are optional.

Try the following expressions to get the language list and the file:

String input = "Some String lang:c,cpp,java file:build.java";
String langExpression = "lang:([\\w,]*)";
String fileExpression = "file:([\w\.]*)";

Patter langPattern = Pattern.compile(langExpression);
Matcher langMatcher = langPattern.matcher(input);
if (langMatcher.matches()) {
  String languageList = langMatcher.group(1);
}

Patter filePattern = Pattern.compile(fileExpression );
Matcher fileMatcher = filePattern.matcher(input);
if (fileMatcher .matches()) { 
  String filename= fileMatcher.group(1);
}

This should work with lang:xxx file:xxx as well as file:xxx lang:xxx as long as the language list or the filename don't contain whitespaces. This would also work if lang: and/or file: was missing.

Would you also expect a string like this: file:build.java Some String lang:c,cpp,java?

answered Apr 18, 2011 at 12:49

Thomas

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2 Comments

Nandish A Over a year ago

Thanks Thomas, I will try this . This will be a very good head start to get regex working for me.

Thomas Over a year ago

@Nandish You could also have a look at regular-expressions.info which IMHO is a very good reference.

kurumi · Accepted Answer · 2011-04-18 12:55:39Z

1

What is so "unmaintainable" about using split?

        String str = "Some String lang:c,cpp,java file:build.java";
        String[] s  = str.split("(lang|file):");

answered Apr 18, 2011 at 12:55

kurumi

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Comments

adarshr · Accepted Answer · 2011-04-18 12:46:59Z

0

While split can do what you want to achieve, you can write your own code using substring and indexOf methods. This will be far faster than using split in terms of performance.

answered Apr 18, 2011 at 12:46

adarshr

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1 Comment

I82Much Over a year ago

If the OP is concerned about maintainability, I guarantee that rolling your own variant of split using substring and indexOf is not going to help in that regard. Furthermore, this smells of premature optimization to me.

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