Sample code for the performance difference among the regular expression quantifiers .

RegExpTest1.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegExpTest1 {

	private static String str = "xfooxxxxxxfoo";
	private static int max = 10000000;
	public static void main(String args[]){

		runGreedy();
		runReluctant();
		runPossessive();
	}
	
	public static void runGreedy(){
		long before = System.currentTimeMillis();
		String regex = ".*foo";

		for(int i = 0; i < max ; i++){
			Pattern p = Pattern.compile(regex);
			Matcher m = p.matcher(str);
			m.find();
		}
		
		long after = System.currentTimeMillis();
		
		System.out.println("greedy :" + (after - before));
	}
	
	public static void runReluctant(){
		long before = System.currentTimeMillis();
		String regex = ".*?foo";

		for(int i = 0; i < max ; i++){	
			Pattern p = Pattern.compile(regex);
			Matcher m = p.matcher(str);

			m.find();
		}
		
		long after = System.currentTimeMillis();
		
		System.out.println("reluctant :" + (after - before));
	}

	public static void runPossessive(){
		long before = System.currentTimeMillis();
		String regex = ".*+foo";

		for(int i = 0; i < max ; i++){
			Pattern p = Pattern.compile(regex);
			Matcher m = p.matcher(str);
			m.find();
		}
		
		long after = System.currentTimeMillis();
		
		System.out.println("possessive :" + (after - before));
	}
}