Introduction
For the best introduction see my article on Regular Expressions . This example shows a random set of examples in Java.
import java.util.regex.*; public class { public static void main(String[] args) { // Compile regular expression String patternStr = "b"; Pattern pattern = Pattern.compile(patternStr); // Determine if pattern exists in input CharSequence inputStr = "a b c b"; Matcher matcher = pattern.matcher(inputStr); boolean matchFound = matcher.find(); // true // Get matching string String match = matcher.group(); // b // Get indices of matching string int start = matcher.start(); // 2 int end = matcher.end(); // 3 // the end is index of the last matching character + 1 // Find the next occurrence matchFound = matcher.find(); // true } }