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.
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.
