Platform and version requirements: JVM (1.0), JS (1.1), Native (1.3)

abstract fun put(key: K, value: V): V?

For Common, JVM

Associates the specified value with the specified key in the map.

This method is redeclared as abstract, because it's not implemented in the base class, so it must be always overridden in the concrete mutable collection implementation.

Return the previous value associated with the key, or null if the key was not present in the map.

For JS, Native

Associates the specified value with the specified key in the map.

Return the previous value associated with the key, or null if the key was not present in the map.