Re: [collections-dev] Question about ConcurrentHashMap

[Mohammad Rezaei <mohdev@xxxxxxxxx>]

try putIfAbsent

Thanks

Moh

On 9/22/23 13:23, Siddharth Jain via collections-dev wrote:

Hi,

I am using EC ConcurrentHashMap. I need a method that does below two operations atomically:

1. returns value of a key

2. if the key is not in the dictionary (i.e., step 1 returns null) it should put a KV pair in the map.

I am trying getIfAbsentPut but it does not return the original value in the map. I want this test to pass:

ConcurrentHashMap<String, String> map = new ConcurrentHashMap<>();

map.put("foo", "bar");

var x = map.getIfAbsentPut("spam", "eggs");

assertTrue(x == null);

is there any method that can do this for me?

S.

PS: i am looking for a behavior somewhat equivalent to AtomicInger getAndIncrement. the get returns the original value not the value after the operation completes.

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