Review

class StrBuilder {
    /**
     * Appends a boolean value to the string builder.
     *
     * @param value  the value to append
     * @return this, to enable chaining
     */
    public StrBuilder append(boolean value) {
        if (value) {
            ensureCapacity(size + 4);
            buffer[size++] = 't';
            buffer[size++] = 'r';
            buffer[size++] = 'u';
            buffer[size++] = 'e';
        } else {
            ensureCapacity(size + 5);
            buffer[size++] = 'f';
            buffer[size++] = 'a';
            buffer[size++] = 'l';
            buffer[size++] = 's';
            buffer[size++] = 'e';
        }
        return this;
    }

}