#vulnerable code 
                                @Override
    public boolean equals(Object obj)
        throws NullPointerException
    {
        if(obj == this)
            return true;

        if( ! (obj instanceof Candidate))
            return false;

        Candidate<?> targetCandidate = (Candidate<?>) obj;

        //compare candidate addresses
        if( ! targetCandidate.getTransportAddress()
                .equals(getTransportAddress()))
            return false;

        //compare bases
        if( getBase() == null )
        {
            if (targetCandidate.getBase() != null)
                return false;
        }

        //compare other properties
        if(((getBase() == this && targetCandidate.getBase() == targetCandidate)
            || getBase().equals(targetCandidate.getBase()))
            && getPriority() == targetCandidate.getPriority()
            && getType() == targetCandidate.getType()
            && getFoundation().equals(targetCandidate.getFoundation()))
        {
            return true;
        }
        return false;
    } 
                            #location 27 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public boolean equals(Object obj)
        throws NullPointerException
    {
        if (obj == this)
            return true;

        if (! (obj instanceof Candidate))
            return false;

        Candidate<?> candidate = (Candidate<?>) obj;

        //compare candidate addresses
        if (! candidate.getTransportAddress().equals(getTransportAddress()))
            return false;

        //compare bases
        Candidate<?> base = getBase();
        Candidate<?> candidateBase = candidate.getBase();
        boolean baseEqualsCandidateBase;

        if (base == null)
        {
            if (candidateBase != null)
                return false;
            else
                baseEqualsCandidateBase = true;
        }
        else
        {
            baseEqualsCandidateBase = base.equals(candidateBase);
        }

        //compare other properties
        return
            (baseEqualsCandidateBase
                    || (base == this && candidateBase == candidate))
                && getPriority() == candidate.getPriority()
                && getType() == candidate.getType()
                && getFoundation().equals(candidate.getFoundation());
    }