ndsvw :
Is there a data structure in Java (java util, guava...) that allows me to store "key value" pairs that can also be interpreted as value-key?
Example:
Datastructure d = new Datastructure();
d.add(1, "foo");
d.add(21 "bar");
d.add(33 "hello");
d.add(55 "world");
A function like d.get1(1) should return foo. A function like d.get2("foo") should return 1.
A function like d.get1(33) should return hello. A function like d.get2("hello") should return 33.
...
Is there something that works like this?
Razib :
What you are looking for is essentially implemented by Guava's BiMap.
You can use guava's BiMap like this -
BiMap<Integer, String> biMap = HashBiMap.create();
biMap.put(1, "foo");
biMap.put(21, "bar");
System.out.println(biMap.get("1"))); //foo
System.out.println(biMap.inverse().get("bar"))); //21
Link:
- Guide to guava BiMap
- BiMap java doc
Alternatively, you can use apache common BiDiMap like this:
BidiMap<String, String> map = new DualHashBidiMap<>();
map.put(1, "foo");
map.put(21, "bar");
System.out.println(map.get(1)); //1
//reversing the mapping
BidiMap<String, String> reversedMap = map.inverseBidiMap();
System.out.println(reversedMap.get("foo")); //1