@Override public final String toString(){
  StringBuilder builder=new StringBuilder();
  for (  SemiCluster v : this) {
    builder.append(v.toString() + " ");
  }
  return builder.toString();
}

@ Override public final String toString ( ) { StringBuilder builder = new StringBuilder ( ) ; for ( SemiCluster v : this ) { builder . append ( v . toString ( ) + " " ) ; } return builder . toString ( ) ; }
returns a string representation of the list .
