Counts how many times the regexp appears in the larger String. - Java Regular Expressions

Java examples for Regular Expressions:Match

  1. HOME
  2. Java
  3. Regular Expressions
  4. Match

Description

Counts how many times the regexp appears in the larger String.

Demo Code

/*/*from   ww  w  .  j a  v  a 2 s .co  m*/
 * Copyright 2013 Guidewire Software, Inc.
 */
/**
 * This class is based, in part, on org.apache.commons.lang.StringUtils and is intended
 * to break the dependency on that project.
 *
 * @author <a href="http://jakarta.apache.org/turbine/">Apache Jakarta Turbine</a>
 * @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a>
 * @author Daniel L. Rall
 * @author <a href="mailto:gcoladonato@yahoo.com">Greg Coladonato</a>
 * @author <a href="mailto:ed@apache.org">Ed Korthof</a>
 * @author <a href="mailto:rand_mcneely@yahoo.com">Rand McNeely</a>
 * @author Stephen Colebourne
 * @author <a href="mailto:fredrik@westermarck.com">Fredrik Westermarck</a>
 * @author Holger Krauth
 * @author <a href="mailto:alex@purpletech.com">Alexander Day Chaffee</a>
 * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
 * @author Arun Mammen Thomas
 * @author Gary Gregory
 * @author Phil Steitz
 * @author Al Chou
 * @author Michael Davey
 * @author Reuben Sivan
 * @author Chris Hyzer
 *  Johnson

 */
//package com.java2s;

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

public class Main {
    public static void main(String[] argv) {
        String str = "java2s.com";
        String regexp = "java2s.com";
        System.out.println(countRegexpMatches(str, regexp));
    }

    /**
     * <p>Counts how many times the regexp appears in the larger String.</p>
     *
     * <p>A <code>null</code> or empty ("") String input returns <code>0</code>.</p>
     *
     * <pre>
     * countMatches(null, *)       = 0
     * countMatches("", *)         = 0
     * countMatches("abba", null)  = 0
     * countMatches("abba", "")    = 0
     * countMatches("abba", "a")   = 2
     * countMatches("abba", "ab")  = 1
     * countMatches("abba", ".b")  = 2
     * countMatches("abba", "xxx") = 0
     * </pre>
     *
     * @param str  the String to check, may be null
     * @param regexp  the regexp to count, may be null
     * @return the number of occurrences, 0 if either String is <code>null</code>
     */
    public static int countRegexpMatches(String str, String regexp) {
        if (isEmpty(str) || isEmpty(regexp)) {
            return 0;
        }
        Pattern pattern = Pattern.compile(regexp);
        Matcher matcher = pattern.matcher(str);
        int i = 0;
        while (matcher.find()) {
            i++;
        }
        return i;
    }

    /**
     * <p>Checks if a String is empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isEmpty(null)      = true
     * StringUtils.isEmpty("")        = true
     * StringUtils.isEmpty(" ")       = false
     * StringUtils.isEmpty("bob")     = false
     * StringUtils.isEmpty("  bob  ") = false
     * </pre>
     *
     * <p>NOTE: This method changed in Lang version 2.0.
     * It no longer trims the String.
     * That functionality is available in isBlank().</p>
     *
     * @param str  the String to check, may be null
     * @return <code>true</code> if the String is empty or null
     */
    public static boolean isEmpty(String str) {
        return str == null || str.length() == 0;
    }

    /**
     * Gets a String's length or <code>0</code> if the String is <code>null</code>.
     *
     * @param str
     *            a String or <code>null</code>
     * @return String length or <code>0</code> if the String is <code>null</code>.
     * @since 2.4
     */
    public static int length(String str) {
        return str == null ? 0 : str.length();
    }
}

Related Tutorials