boolean isNameUsed(String name){
  List<Integer> columnsWithName=columnNames.get(name);
  return columnsWithName != null && !columnsWithName.isEmpty();
}

boolean isNameUsed ( String name ) { List < Integer > columnsWithName = columnNames . get ( name ) ; return columnsWithName != null && ! columnsWithName . isEmpty ( ) ; }
checks if the given column name is already in use .
