/**
     * @see java.lang.Object#equals(java.lang.Object)
     */
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        } else if (!(o instanceof Extension)) {
            return false;
        } else {
            Extension e = (Extension) o;
            return java.util.Objects.equals(e.getArtifactId(), getArtifactId())