In this example we shall show you how to find occurances of a specific letter in a String. To find occurances of a letter in a String one should perform the following steps:
- Compile a given String regular expression to a Pattern, using
compile(string regex)API method of Pattern. The given regex in the example is a word boundary followed by character “A”, then a character of any letter one or more times and then a word boundary again. - Use
matcher(CharSequence input)API method of Pattern to create a Matcher that will match the given String input against this pattern. - While the matcher finds the next subsequence of the input sequence that matches the pattern, with
find()API method of Matcher get the input subsequence matched, withgroup()API method of Matcher and print it,
as described in the code snippet below.
package com.javacodegeeks.snippets.core;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Main {
public static void main(String args[]) throws Exception {
String candidate = "this is a test, A TEST.";
String regex = "\bA\\w*\b";
Pattern p = Pattern.compile(regex);
Matcher m = p.matcher(candidate);
String val = null;
System.out.println("INPUT: " + candidate);
System.out.println("REGEX: " + regex + "rn");
while (m.find()) {
val = m.group();
System.out.println("MATCH: " + val);
}
if (val == null) {
System.out.println("NO MATCHES: ");
}
}
}
Output:
INPUT: this is a test, A TEST.
REGEX: bAw*b
MATCH: A
This was an example of how to find occurances of a letter in a String in Java.
