Mar 6, 2010 · I have a Map that uses a Set for the key type, like this: Map<Set<Thing>, Val> map; When I query map.containsKey(myBunchOfThings), it returns false, and I don't understand …

Specified by: keySet in interface Map Overrides: keySet in class AbstractMap Returns: a set view of the keys contained in this map. so if you have a map myMap of any datatype , such that the …

May 5, 2012 · What I'll do which is very simple but waste memory is to map the values with a key and do the oposite to map the keys with a value making this: private Map<Object, Object> …

Something to keep in mind is that the value will initially be null, so the first time you use a key, you'll have to initialize it:

Jan 23, 2012 · Moreover, loop over the entrySet is faster, because you don't query the map twice for each key. Also Map.Entry implementations usually implement the toString() method, so you …

In Java 8. To sort a Map<K, V> by key, putting keys into a List<K>: List<K> result = map.keySet().stream().sorted().collect(Collectors.toList()); To sort a Map<K, V> by key, putting …

You can grab the keySet of the map and then filter to get only keys that starts with "address" and add the valid keys to a new Set. With Java 8, it's a bit less verbose: Set<String> set = …

To keep Map< Integer , String > in an order sorted by key, use either of the two classes implementing the SortedMap/NavigableMap interfaces: TreeMap; ConcurrentSkipListMap …

ARecords in you map are not the keys, they are values! You have to decide list of what entities you want to get in the end: ARecords or Strings. If ARecords - then take values of a Map, if …

Feb 25, 2009 · Assuming K is your key type and V is your value type: for (Map.Entry<K,V> entry : map.entrySet()) { K key = entry.getKey(); V value = entry.getValue(); // do stuff } This version …