How does WeakHashMap behave in multithreaded code?

A WeakHashMap in Java is a type of Map that allows keys to be garbage collected when there are no strong references to them. This behavior can lead to issues in multithreaded applications if not handled properly.

In a multithreaded environment, a WeakHashMap can lead to unpredictable behavior, such as sudden removal of keys that are still being accessed by other threads. Because of its nature, the keys in a WeakHashMap can disappear while other threads are still trying to read or manipulate the map, leading to ConcurrentModificationExceptions or inconsistent data reads.

To safely use a WeakHashMap in a multithreaded scenario, it is essential to use proper synchronization mechanisms or consider using concurrent collections such as ConcurrentHashMap which are designed for multithreading.