Review

class StrBuilder {
    /**
     * Checks whether this builder starts with the specified string.
     * <p>
     * Note that this method handles null input quietly, unlike String.
     * 
     * @param str  the string to search for, null returns false
     * @return true if the builder starts with the string
     */
    public boolean startsWith(String str) {
        if (str == null) {
            return false;
        }
        int len = str.length();
        if (len == 0) {
            return true;
        }
        if (len > size) {
            return false;
        }
        for (int i = 0; i < len; i++) {
            if (buffer[i] != str.charAt(i)) {
                return false;
            }
        }
        return true;
    }

}