Compile Reg Ex pattern with multiple flags

Byron KiourtzoglouNovember 11th, 2012Last Updated: August 19th, 2013

0 97 1 minute read

With this example we shall show you how to compile regular expression to a Pattern with multiple flags. Compiling a regular expression to a Pattern with multiple flags implies that you should:

Compile a String regular expression to a Pattern, using compile(String regex) API method of Pattern.
Use matcher(CharSequence input) API method of Pattern to create a Matcher that will match the given String input against this pattern.
Use find() API method to find the next subsequence of the input sequence that matches the pattern.
Compile the same regular expression to a Pattern, using compile(String regex, int flags) API method of Pattern. This pattern has a case-sensitive matching or a multiline mode.
Use matcher(CharSequence input) and find() API methods again for the new pattern.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.core;

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

public class CompileRegExPatternWithMultipleFlags {
	
	public static void main(String[] args) {
		
		Pattern pattern;
		Matcher matcher;
		boolean matchFound;
		
		CharSequence inputStr = "Abcndef";
		String patternStr = "abc$";
		
		// Compile with default flags
		pattern = Pattern.compile(patternStr);
		
		matcher = pattern.matcher(inputStr);
		matchFound = matcher.find(); // false

		// Compile with MULTILINE and CASE_INSENSITIVE flags enabled
		pattern = Pattern.compile(
				patternStr,
				Pattern.MULTILINE | Pattern.CASE_INSENSITIVE
		);
		
		matcher = pattern.matcher(inputStr);
		matchFound = matcher.find(); // true
		
	}

}

This was an example of how to compile regular expression to a Pattern with multiple flags in Java.