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# stdlib
c
christophsturm
07/09/2021, 12:02 PMwhat is the difference between ConcurrentMap getOrPut and computeIfAbsent?
e
enleur
07/09/2021, 12:14 PMcomputeIfAbsent does not work with nulls
Copy code
mutableMapOf<String, Int?>().apply {
getOrPut("b") { null}
} // {b=null}
mutableMapOf<String, Int?>().apply {
computeIfAbsent("b") { null}
} // {}👍 1
d
dmitriy.novozhilov
07/09/2021, 12:25 PM Copy code
/**
* Concurrent getOrPut, that is safe for concurrent maps.
*
* Returns the value for the given [key]. If the key is not found in the map, calls the [defaultValue] function,
* puts its result into the map under the given key and returns it.
*
* This method guarantees not to put the value into the map if the key is already there,
* but the [defaultValue] function may be invoked even if the key is already in the map.
*/
public inline fun <K, V> ConcurrentMap<K, V>.getOrPut(key: K, defaultValue: () -> V): V {
// Do not use computeIfAbsent on JVM8 as it would change locking behavior
return this.get(key)
?: defaultValue().let { default -> this.putIfAbsent(key, default) ?: default }
}👍 1
c
christophsturm
07/09/2021, 12:58 PM@dmitriy.novozhilov actually i did read the kdoc and wondered why it does not explain whats different from computeIfAbsent
d
dmitriy.novozhilov
07/12/2021, 8:05 AMConcurrentHashMap.putIfAbsentkeygetOrPut27 Views