Module org.apache.sis.util
Package org.apache.sis.util.collection

Interface Cache.Handler<V>

Type Parameters:
V - the type of value objects.
Enclosing class:
Cache<K,V>
public static interface Cache.Handler<V>
The handler returned by Cache​.lock(K), to be used for unlocking and storing the result. This handler should be used as below (the try … finally statements are important): 
Value V = null;
Cache.Handler<V> handler = cache.lock(key);
try {
    value = handler.peek();
    if (value == null) {
        value = createMyObject(key);
    }
} finally {
    handler.putAndUnlock(value);
}
See the Cache javadoc for a more complete example.
Since:
0.3

  • Method Summary

    Modifier and Type
    Method
    Description
    V
    peek()
    If the value is already in the cache, returns it.
    void
    put­And­Unlock(V result)
    Stores the given value in the cache and release the lock.

  • Method Details

    • peek

      V peek()
      If the value is already in the cache, returns it. Otherwise returns null. This method should be invoked after the Handler creation in case a value has been computed in another thread.
      Returns:
      the value from the cache, or null if none.

    • putAndUnlock

      void putAndUnlock(V result) throws IllegalStateException
      Stores the given value in the cache and release the lock. This method must be invoked in a finally block, no matter what the result is.
      Parameters:
      result - the result to store in the cache, or null for removing the entry from the cache. If an entry is removed, a new computation will be attempted the next time a handler is created for the same key.
      Throws:
      Illegal­State­Exception - may be thrown if this method is not invoked in the pattern described in class javadoc, or if a key collision occurs.