Chapter 6.3: Pattern and Matcher

For advanced regular expressions the java.util.regex.Pattern and java.util.regex.Matcher classes are used.

You first create a Pattern object which defines the regular expression. This Pattern object allows you to create a Matcher object for a given string. This Matcher object then allows you to do regex operations on a String.

package de.vogella.regex.test;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class RegexTestPatternMatcher {

  public static final String EXAMPLE_TEST = "This is my small example string which I'm going to use for pattern matching.";

  public static void main(String[] args) {

    Pattern pattern = Pattern.compile("\\w+");

    // in case you would like to ignore case sensitivity,

    // you could use this statement:

    // Pattern pattern = Pattern.compile("\\s+", Pattern.CASE_INSENSITIVE);

    Matcher matcher = pattern.matcher(EXAMPLE_TEST);

    // check all occurance

    while (matcher.find()) {

      System.out.print("Start index: " + matcher.start());

      System.out.print(" End index: " + matcher.end() + " ");

      System.out.println(matcher.group());

    }

    // now create a new pattern and matcher to replace whitespace with tabs

    Pattern replace = Pattern.compile("\\s+");

    Matcher matcher2 = replace.matcher(EXAMPLE_TEST);

    System.out.println(matcher2.replaceAll("\t"));

  }

}