wtf.metio.yosql.internals.jdk.Buckets Maven / Gradle / Ivy
/*
* This file is part of yosql. It is subject to the license terms in the LICENSE file found in the top-level
* directory of this distribution and at https://creativecommons.org/publicdomain/zero/1.0/. No part of yosql,
* including this file, may be copied, modified, propagated, or distributed except according to the terms contained
* in the LICENSE file.
*/
package wtf.metio.yosql.internals.jdk;
import java.util.Collection;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Stream;
/**
* Utility methods that handle {@link Collection collections} and {@link Stream streams}. The class is called "Buckets"
* because 'Collections' is way too common.
*/
public final class Buckets {
/**
* @param collection The collection to check.
* @return true if value is not null and not empty, false otherwise.
*/
public static boolean hasEntries(final Collection collection) {
return collection != null && !collection.isEmpty();
}
/**
* Allows to use {@link Stream#distinct()} with a key.
*
* @param keyExtractor The function to extract the key from an object.
* @param The type of the object in the stream.
* @return A filter to use with @{@link Stream#filter(Predicate)}.
*/
public static Predicate distinctByKey(final Function keyExtractor) {
final var seen = ConcurrentHashMap.newKeySet();
return object -> seen.add(keyExtractor.apply(object));
}
private Buckets() {
// utility class
}
}