Java String Match Count countMatches(String str, String sub)

Description

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

A null or empty ("") String input returns 0.

 StringUtils.countMatches(null, *)       = 0 StringUtils.countMatches("", *)         = 0 StringUtils.countMatches("abba", null)  = 0 StringUtils.countMatches("abba", "")    = 0 StringUtils.countMatches("abba", "a")   = 2 StringUtils.countMatches("abba", "ab")  = 1 StringUtils.countMatches("abba", "xxx") = 0 

License

Open Source License

Parameter

Parameter	Description
str	the String to check, may be null
sub	the substring to count, may be null

Return

the number of occurrences, 0 if either String is null

Declaration

public static int countMatches(String str, String sub) 

Method Source Code

//package com.java2s;

public class Main {
    /**//from ww  w  . j  a v  a2  s .  c o m
     * <p>Counts how many times the substring appears in the larger String.</p>
     * <p/>
     * <p>A <code>null</code> or empty ("") String input returns <code>0</code>.</p>
     * <p/>
     * <pre>
     * StringUtils.countMatches(null, *)       = 0
     * StringUtils.countMatches("", *)         = 0
     * StringUtils.countMatches("abba", null)  = 0
     * StringUtils.countMatches("abba", "")    = 0
     * StringUtils.countMatches("abba", "a")   = 2
     * StringUtils.countMatches("abba", "ab")  = 1
     * StringUtils.countMatches("abba", "xxx") = 0
     * </pre>
     *
     * @param str the String to check, may be null
     * @param sub the substring to count, may be null
     * @return the number of occurrences, 0 if either String is <code>null</code>
     */
    public static int countMatches(String str, String sub) {
        if (isEmpty(str) || isEmpty(sub)) {
            return 0;
        }
        int count = 0;
        int idx = 0;
        while ((idx = str.indexOf(sub, idx)) != -1) {
            count++;
            idx += sub.length();
        }
        return count;
    }

    /**
     * checks for null and zero length
     *
     * @param s the string
     * @return true if null or zero length
     */
    public static boolean isEmpty(final String s) {
        return s == null || s.length() == 0;
    }
}

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