In this example we shall show you how to check if a String matches a Pattern. To check if a String matches a Pattern one should perform the following steps:
- 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
matches()API method of Matcher to match the entire region against the pattern. It returns true if, and only if, the entire region sequence matches this matcher’s pattern. - Reset the matcher with a new input sequence, with
reset(CharSequence input)API method of Matcher. - Match the input sequence, starting at the beginning of the region, against the pattern, using
lookingAt()API method of Matcher,
as described in the code snippet below.
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 | package com.javacodegeeks.snippets.core;import java.util.regex.Matcher;import java.util.regex.Pattern;public class CheckIfAStringMatchesAPattern { public static void main(String[] args) { String patternStr = "test"; Pattern pattern = Pattern.compile(patternStr); String input = "this fails"; // create a matcher that will match the given input against this pattern Matcher matcher = pattern.matcher(input); boolean matchFound = matcher.matches(); System.out.println(input + " - matches: " + matchFound); input = "this passes the test"; // reset the matcher with a new input sequence matcher.reset(input); matchFound = matcher.matches(); System.out.println(input + " - matches: " + matchFound); // Attempts to match the input sequence, starting at the beginning // of the region, against the pattern matchFound = matcher.lookingAt(); System.out.println(input + " - matches from the beginning: " + matchFound); }} |
Output:
this fails - matches: false
this passes the test - matches: false
this passes the test - matches from the beginning: false
This was an example of how to check if a String matches a Pattern in Java.
