code: public static int countMatches(final CharSequence str, final char ch) {
  		if (isEmpty(str)) {
  			return 0;
  		}
  		int count = 0;
  		// We could also call str.toCharArray() for faster look ups but that
  		// would generate more garbage.
  		for (int i = 0; i < str.length(); i++) {
  			if (ch == str.charAt(i)) {
  				count++;
  			}
  		}
  		return count;
  	}
docs: <p>
  Counts how many times the char appears in the given string.
  </p>
  
  <p>
  A {@code null} or empty ("") String input returns {@code 0}.
  </p>
  
  <pre>
  StringUtils.countMatches(null, *)       = 0
  StringUtils.countMatches("", *)         = 0
  StringUtils.countMatches("abba", 0)  = 0
  StringUtils.countMatches("abba", 'a')   = 2
  StringUtils.countMatches("abba", 'b')  = 2
  StringUtils.countMatches("abba", 'x') = 0
  </pre>
  
  @param str
  the CharSequence to check, may be null
  @param ch
  the char to count
  @return the number of occurrences, 0 if the CharSequence is {@code null}
  @since 3.4