question: public boolean overlapSave ( SphereCluster other ) { double minDist = Math . sqrt ( 2 ) * ( getRadius ( ) + other . getRadius ( ) ) ; double diff = getCenterDistance ( other ) - minDist ; return diff > 0 ; }
target:  When a clusters looses points the new minimal bounding sphere can be partly outside of the originating cluster. If a another cluster is right next to the original cluster (without overlapping), the new cluster can be overlapping with this second cluster. OverlapSave will tell you if the current cluster can degenerate so much that it overlaps with cluster 'other'