Java Programming help

Question

I have a method that returns Sets of sets. Following is what I mean:

public static HashSet methodName(){
 HashSet c= new HashSet(); 

 c.add(x); //x is a HashSet of number
 c.add(y); //y is a Hashset of numbers

 return c;
}

After the method returns the collections, I enter it into an arraylist

ArrayList<HashSet> xxx= new ArrayList<Hashset>();
y=methodName();
xxx.add(y);

The method gets called couple of times and each time I enter sets of sets into the arraylist.

My question is. now I want to go through the arraylist and find the set that contains the smallest number of sets. How do I do that? Thanks so much in advance. Any help will be appreciated.

Answer 1

A simple way you to go through an array is through an Iterator. These are utilized in a foreach loop, which can be used when you know the type of elements used in an array (via generics). You can use that in your outer HashSet- containing ArrayList:

for (HashSet set : xxx) {
    // you need to iterate over the elements in your HashSet here and determine which internal Set has the most elements
    for ( Iterator iter = set.iterator(); iter.hasNext();) {
        HashSet innerSet = (HashSet) iter.next();
        // do the size test
     }

}

Answer 2

The size() method gives the cardinality of a HashSet. Simply write a Comparator<HashSet> and use Collections.max().