fm.common.ThreadLocalHashMap.scala Maven / Gradle / Ivy
/*
* Copyright 2016 Frugal Mechanic (http://frugalmechanic.com)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package fm.common
import scala.collection.mutable
/**
* Wraps a Scala mutable.HashMap inside of a ThreadLocal and exposes
* some simple operations.
*
* The initial use case of this is for caching NumberFormat instances
* by Locale. This can be accomplished by overriding the initialValue
* method and just calling the apply() method with the Locale.
*
* @tparam K The HashMap Key
* @tparam V The HashMap Value
*/
class ThreadLocalHashMap[K,V] {
private val threadLocal: ThreadLocal[mutable.HashMap[K,V]] = new ThreadLocal[mutable.HashMap[K,V]]{
override def initialValue: mutable.HashMap[K,V] = new mutable.HashMap[K,V]
}
private def getMap: mutable.HashMap[K,V] = threadLocal.get()
final def apply(key: K): V = get(key).getOrElse{ throw new NoSuchElementException(key.toString) }
final def get(key: K): Option[V] = {
val m: mutable.HashMap[K,V] = getMap
val res: Option[V] = m.get(key)
if (res.isDefined) res else {
val init: Option[V] = initialValue(key)
if (init.nonEmpty) m(key) = init.get
init
}
}
final def update(key: K, value: V): Unit = getMap.update(key, value)
protected def initialValue(key: K): Option[V] = None
}
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