java - Iterating over hashmap

The 'Map' data structure isn't a Collection object but Sets are.

The most common method to iterate over a Map is using the underlying .entrySet method.

// For each loop
for ( Entry entry : names ) {
    System.out.println( String.format( "(%s, %s)", entry.getKey(), entry.getValue() ) );
}
// Iterator
Iterator iterator = names.entrySet().iterator
while( iterator.hasNext() ){
     Entry entry = iterator.next()
     System.out.println( String.format( "(%s, %s)", entry.getKey(), entry.getValue() ) );
}

If are interested in finding the total number of Map nodes, use the .size() method.

EDIT:

Since you want the total size of each list stored within the map, you could do something like this.

Iterator iterator = names.entrySet().iterator
int count = 0;
while( iterator.hasNext() ){
     Entry entry = iterator.next()
     count += entry.getValue().size()
}