Package org.apache.sis.util.collection
Interface Cache.Handler<V>
- Type Parameters:
V- the type of value objects.
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
Defined in the sis-utility module
-
Method Summary
Modifier and TypeMethodDescriptionpeek()If the value is already in the cache, returns it.voidputAndUnlock(V result) Stores the given value in the cache and release the lock.
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Method Details
-
peek
V peek()If the value is already in the cache, returns it. Otherwise returnsnull. This method should be invoked after theHandlercreation in case a value has been computed in another thread.- Returns:
- the value from the cache, or
nullif none.
-
putAndUnlock
Stores the given value in the cache and release the lock. This method must be invoked in afinallyblock, no matter what the result is.- Parameters:
result- the result to store in the cache, ornullfor 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.
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