org.opendaylight.infrautils.caches.CacheFunction Maven / Gradle / Ivy
/*
* Copyright (c) 2017 Red Hat, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.infrautils.caches;
import com.google.common.collect.ImmutableMap;
import java.util.function.Function;
import org.eclipse.jdt.annotation.NonNull;
/**
* {@link Cache}'s Function.
*
* Use this if your implementation throws no exception (i.e. only unchecked
* runtime exceptions). If your cache function throws checked exceptions, then
* just use a {@link CheckedCacheFunction} instead.
*
* @author Michael Vorburger.ch
*/
@FunctionalInterface
public interface CacheFunction {
/**
* Calculate the value of the cache entry for the given key.
* @param key the key for which to "calculate" (lookup, remote call, ...) a value.
* @return value for the given key
*/
@NonNull V get(@NonNull K key);
/**
* Implementations may wish to override this implementation
* if they can provide bulk implementations which avoid 1-by-1
* locking overhead which single get() may incur, which is what
* the default implementation does.
*
* @param keys list of keys of cache entries
* @return Map of cache keys and values (neither ever null, but may be an Optional)
*/
default ImmutableMap get(Iterable keys) {
ImmutableMap.Builder mapBuilder = ImmutableMap.builder();
for (K key : keys) {
mapBuilder.put(key, get(key));
}
return mapBuilder.build();
}
/**
* Convenience mapping from java.util.function.Function.
* Typically never overridden.
*/
default CacheFunction from(Function function) {
return function::apply;
}
}