find all possible combinations of arraylists java

i need to find all combos of the iceCream and toppings lists and this code:

import java.util.ArrayList;

public class IceCream {

    public long printMenu( )
    {
        String iceCream[] = {" ", "chocolate", "vanilla", "strawberry"};
        String toppings[] = {" ", "sprinkles", "whipped cream", "chocolate chips"};

        ArrayList<String> menuList = new ArrayList<String>();
        long menu_num = 0;

        for (int x = 0; x < iceCream.length; x++)
        {
            for (int y = 0; y < toppings.length; y++)
            {
                menu_num++;
                menuList.add(iceCream[x] + " " +  toppings[y]);
            }
        }

        System.out.println(menuList);
        return menu_num;
    }

    public static void main( String [ ] args ) {
        IceCream obj = new IceCream( );
        long count = obj.printMenu( );
        System.out.println(count);
        assert count == 32;
    }

            }

outputs

[   ,   sprinkles,   whipped cream,   chocolate chips, chocolate  , chocolate sprinkles, chocolate whipped cream, chocolate chocolate chips, vanilla  , vanilla sprinkles, vanilla whipped cream, vanilla chocolate chips, strawberry  , strawberry sprinkles, strawberry whipped cream, strawberry chocolate chips]
16

Process finished with exit code 0

i need to be able to have more than one topping on each ice cream and print out 32 combos total. any help is appreciated

If the goal is to find out different toppings combination for each ice cream type, the ideal way is to use Guava's Sets.powerset(Set set).

Sets.powerset(Set set) will return all the combination of subsets of the set.
In your case you can generate a powerset as below,

String toppings[] = {" ", "sprinkles", "whipped cream", "chocolate chips"};

// Creating a set from toppings array
Set<String> set = Sets.newHashSet(Arrays.asList(toppings));  

// powerSet to store all subsets of a set 
// The powerset will contain all the combination of toppings as subsets
// Ex: [ , whipped cream, sprinkles], [ , whipped cream, sprinkles, chocolate chips], ...
Set<Set<String>> powerSet = Sets.powerSet(set); 

Now that you have the powerSet with subset of combinations, you can iterate over and convert each subset to a combination of topping strings as below,

// This set is to concatinate the entries of the subset (of the powerset) and store as a string
Set<String> toppingsCombinationSet = Sets.newHashSet();

for (Set<String> s : powerSet) {
    String toppings = "";
    for (String topping : s) {
        toppings = toppings.trim() + " " + topping.trim();
    }
    toppingsCombinationSet.add(toppings);       
}

Finally you can combine the ice cream type to the combination of toppings as below,

// Combine the ice Cream to the toppings combination
// Whitespaces need to be removed as it doesn't make any sense to have values like : "sprinkles chocolate chips" (without ice cream type)
for (int x = 0; x < iceCream.length; x++) { 
    if (!" ".equals(iceCream[x])) {
        for (String topping : toppingsCombinationSet) {
            if (!" ".equals(topping)) {
                String s = (iceCream[x].trim() + " " +  topping.trim()).trim();
                menuList.add(s);
            }    

        }
            
    }
}

You are almost there.

In your code, you have the following:

• a loop to loop through the ice cream flavors
• a loop to loop through the first layer of toppings

But you are having trouble trying to put the second topping on there, yes? If so, would it not make sense to have yet another loop for the second layer of toppings?

    for (int x = 0; x < iceCream.length; x++)
    {

        for (int y = 0; y < toppings.length; y++)
        {

            for (int z = 0; z < toppings.length; z++)
            {

                menu_num++;
                menuList.add(iceCream[x] + " " +  toppings[y] + " " toppings[z]);

            }

        }

    }

Now, if you run this, you will notice that there are some duplicates and reorderings. If you need to get rid of those, let me know.