May 30, 2009 · Since the requirements only asks for a random value from the HashMap, here's the approach: The HashMap has a values method which returns a Collection of the values in the map. The Collection is used to create a List. The size method is used to find the size of the List, which is used by the Random.nextInt method to get a random index of the List.

Dec 5, 2013 · You can use it as map: map.get("v2"); and as list: new ArrayList(map.values().values()).get(2); If you want to can write your own 5 lines long class that implements this logic.

Mar 29, 2012 · Use reservoir sampling to select a list of random keys, then insert them into a map (along with their corresponding values in the source map.) This way you do not need to copy the whole keySet into an array, only the selected keys.

Jan 9, 2025 · There are two interfaces for implementing Map in Java. They are Map and SortedMap, and three classes: HashMap, TreeMap, and LinkedHashMap. This method is used in Java Map Interface to clear and remove all of the elements or mappings from a …

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I'm aiming for a map system like The Binding of Isaac's, if that helps. It looks like you need to have the rooms easily query-able by their position. I'd suggest a Map<Vector2d,Room> for quick and dirty, but you might want to put together a sorted array of sorted arrays.

You can combine numbers to create a seed for your random function. This is simple, create a new Random() object for each chunk, using that chunk's position as the seed. If you think of Random as a really (really) long series of numbers, the seed is just where to start iterating through.

Since Java 8, there is an O(log(N)) approach with O(log(N)) additional memory: create a Spliterator via map.entrySet().spliterator(), make log(map.size()) trySplit() calls and choose either the first or the second half randomly.

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