Overriding equals in Groovy

I was overriding equals method in for a Groovy class and got into StackOverflow error.

class ObjKey {
    long id
    String value

    public boolean equals(Object obj) {
        if (!(obj instanceof ObjKey)) {
            return false;
        }
        if (this == obj) {
            return true;
        }
        ObjKey rhs = (ObjKey) obj;
        return new EqualsBuilder()
            .append(id, rhs?.id)
            .append(value, rhs?.value)
            .isEquals();
    }

    public int hashCode() {
        return new HashCodeBuilder()
        .append(id)
        .append(value)
        .toHashCode();
    }
}

I was getting stackoverflow at line: if (this == obj). Groovy's equals calls the equals method instead of comparing the reference.

I fixed it using bellow syntax: if (this.is(obj)). The corrected code looks like:

class ObjKey {
    long id
    String value

    public boolean equals(Object obj) {
        if (!(obj instanceof ObjKey)) {
            return false;
        }
        if (this.is(obj)) {
            return true;
        }
        ObjKey rhs = (ObjKey) obj;
        return new EqualsBuilder()
            .append(id, rhs?.id)
            .append(value, rhs?.value)
            .isEquals();
    }

    public int hashCode() {
        return new HashCodeBuilder()
        .append(id)
        .append(value)
        .toHashCode();
    }
}