Module io.netty5.common
Package io.netty5.util.concurrent

Class FastThreadLocal<V>

  • Type Parameters:
    V - the type of the thread-local variable
    public class FastThreadLocal<V>
extends Object
    A special variant of ThreadLocal that yields higher access performance when accessed from a FastThreadLocalThread.

    Internally, a FastThreadLocal uses a constant index in an array, instead of using hash code and hash table, to look for a variable. Although seemingly very subtle, it yields slight performance advantage over using a hash table, and it is useful when accessed frequently.

    To take advantage of this thread-local variable, your thread must be a FastThreadLocalThread or its subtype. By default, all threads created by DefaultThreadFactory are FastThreadLocalThread due to this reason.

    Note that the fast path is only possible on threads that extend FastThreadLocalThread, because it requires a special field to store the necessary state. An access by any other kind of thread falls back to a regular ThreadLocal.

    See Also:
    ThreadLocal

    • Constructor Detail

      • FastThreadLocal

        public FastThreadLocal()

    • Method Detail

      • removeAll

        public static void removeAll()
        Removes all FastThreadLocal variables bound to the current thread. This operation is useful when you are in a container environment, and you don't want to leave the thread local variables in the threads you do not manage.

      • size

        public static int size()
        Returns the number of thread local variables bound to the current thread.

      • destroy

        public static void destroy()
        Destroys the data structure that keeps all FastThreadLocal variables accessed from non-FastThreadLocalThreads. This operation is useful when you are in a container environment, and you do not want to leave the thread local variables in the threads you do not manage. Call this method when your application is being unloaded from the container.

      • get

        public final V get()
        Returns the current value for the current thread

      • getIfExists

        public final V getIfExists()
        Returns the current value for the current thread if it exists, null otherwise.

      • set

        public final void set​(V value)
        Set the value for the current thread.

      • isSet

        public final boolean isSet()
        Returns true if and only if this thread-local variable is set.

      • remove

        public final void remove()
        Sets the value to uninitialized for the specified thread local map. After this, any subsequent call to get() will trigger a new call to initialValue().

      • initialValue

        protected V initialValue()
                  throws Exception
        Returns the initial value for this thread-local variable.
        Throws:
        Exception

      • onRemoval

        protected void onRemoval​(V value)
                  throws Exception
        Invoked when this thread local variable is removed by remove(). Be aware that remove() is not guaranteed to be called when the `Thread` completes which means you can not depend on this for cleanup of the resources in the case of `Thread` completion.
        Throws:
        Exception