drools-eclipse/org.drools.eclipse/src/main/java/org/drools/eclipse/editors/rete/model/GraphicalVertex.java
public void addConnection(Connection conn) {
        if ( conn == null || conn.getSource() == conn.getTarget() ) {
            throw new IllegalArgumentException();
        }
        if ( conn.getSource() == this ) {
            sourceConnections.add( conn );
            firePropertyChange( SOURCE_CONNECTIONS_PROP,
                                null,
                                conn );
        } else if ( conn.getTarget() == this ) {
            targetConnections.add( conn );
            firePropertyChange( TARGET_CONNECTIONS_PROP,
                                null,
                                conn );
        }
    }
public void addConnection(Connection conn) {
        if ( conn == null || conn.getSource() == conn.getTarget() ) {
            throw new IllegalArgumentException();
        }
        if ( conn.getSource() == this ) {
            sourceConnections.add( conn );
            firePropertyChange( SOURCE_CONNECTIONS_PROP,
                                null,
                                conn );
        } else if ( conn.getTarget() == this ) {
            targetConnections.add( conn );
            firePropertyChange( TARGET_CONNECTIONS_PROP,
                                null,
                                conn );
        }
    }
Add an incoming or outgoing connection to this vertex.
@param conn a non-null connection instance
@throws IllegalArgumentException if the connection is null or has not distinct endpoints