Greedy and Non-Greedy Matching in a Regular Expression

This section illustrates you how to match a string in the given string through the Greedy and Non-Greedy way of matching. Here you can learn about the Greedy and Non-Greedy way of matching the word.

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Greedy and Non-Greedy Matching in a Regular Expression

     

This section illustrates you how to match a string in the given string through the Greedy and Non-Greedy way of matching. Here you can learn about the Greedy and Non-Greedy way of matching the word. Through this method or way you can easily search the appropriate string or text from the given string or text or from the file content according to the requirement of the application. In this section, an example is given for the best illustration of that. You can simply copy and paste the code of the program in your java application for the easy search or match of the string or text in the appropriate source of the content in which something has to be searched or matched.

Greedy Matching: This is the way of matching string from one to another. In this method, the matcher returns that word of the complete content of the file or the string or text in which all the characters of the search string is found.

Non-Greedy Matching: In this way of the matching, string is searched in the complete string or text inputed by the user or the contents of the file upto last characters till any character of the searched string is found in the complete string or text in which another one is searched. In this way of matching, the matcher returns all the words or character from the whole string or text where from no any characters are fond in the string or text which is not present in the searched string or text.

Program Result:

This program takes a collection of string or text in which the specified string has to be searched and replace from the another specified character or word. This program implements both way of matching (Greedy and Non-Greedy). Through the Greedy way of matching, in the given string or text, "abc" is searched and if matcher finds the word, the complete word, which is started with the character "a" and ends with the character "c", is replaced with the character "F".

And in the Non-Greedy way of matching, "abc" is searched in the given string and from start to end till any character is fond in the complete string or text or content of the file. In this way, matcher returns the word or string in which no any character of the searched string is available.

Code Description:

"a.+?c":
This is the regular expression which is used in the following program for the Non-Greedy search or matching from the given string or the content of the file.

"a.*c":
This is also a regular expression of java programming language which performs the Greedy search or matching from the given string or the content of the file.

Here is the code of the program:

import java.util.regex.*;
import java.io.*;

public class GreedyAndNonGreedyMatching{
  public static void main(String[] argsthrows IOException{
  BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
//  System.out.print("Enter string/text in which search 
operation will be performed: ");

  String string = in.readLine();
//  Non-Greedy Matching.
  Pattern pattern = Pattern.compile("a.+?c");
  Matcher matcher = pattern.matcher(string);
  String str = matcher.replaceAll("F");
  System.out.println(str);

//  Greedy Matching.
  pattern = Pattern.compile("a.*c");
  matcher = pattern.matcher(string);
  str = matcher.replaceAll("z");
  System.out.println(string);
  System.out.println(str);
  }
}

Download this example.

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December 22, 2011
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