CODEWITHSUNDEEP
javasearchwildcard
Minions
Minions

Reputation: 5477

wildcard search using replace function

I tried to implement wildcards search in my application using some algorithms (k-gram algorithm etc.), but it was very complex.

Until i found this code, and it works perfectly .. but i don't know how it get check and get results !

Code:

public static boolean wildCardMatch(String text, String pattern)
{
  return text.matches( pattern.replace("?", ".?").replace("*", ".*?") );
}

Does their anyone help me to knows how it work ? what's the idea of replace function?

Upvotes: 3

Views: 2318

Answers (2)

mkierc
mkierc

Reputation: 1188

The method you are using is String.replace(CharSequence target, CharSequence replacement).

It takes two objects implementing CharSequence interface as parameters, which might be one of following:

  • CharBuffer
  • Segment

  • String

  • StringBuffer
  • StringBuilder

And replaces every occurence of first CharSequence with second CharSequence in a String.

In your case, if the pattern parameter would contain **??, the text.matches method would get .?.?.*?.*? as the input, and that's what the text parameter must've contain as well (in terms of regular expressions), in order to successfully match them and the method to return true.

To clarify:

Difference between .*? and .* for regex

Upvotes: 1

Olivier Grégoire
Olivier Grégoire

Reputation: 35457

What you're speaking about is called the glob pattern.

In the Java world, the glob pattern is more often translated into a regex pattern.

In your scenario, the implementation is very basic: the replace method is used to replace all occurrences of ? into the regex equivalent .?. Then all occurences of * are replaced by .*?.

So if you have the following glob pattern: abc*.def, the regex will become abc.*?.def.

When the regex is finally ready, it is used to be checked against the variable text using the method matches. This latter method accepts a regex as input.

Upvotes: 3

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