2 * Copyright (c) 2020 PANTHEON.tech, s.r.o. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.yangtools.yang.parser.rfc7950.stmt;
10 import com.google.common.collect.ImmutableList;
11 import org.eclipse.jdt.annotation.NonNull;
12 import org.opendaylight.yangtools.yang.model.api.meta.ModelStatement;
14 abstract class AbstractModelStatement<A> implements ModelStatement<A> {
17 * Utility method for squashing singleton lists into single objects. This is a CPU/mem trade-off, which we are
18 * usually willing to make: for the cost of an instanceof check we can save one object and re-create it when needed.
19 * The inverse operation is #unmaskSubstatements(Object)}.
21 * @param list list to mask
23 * @throws NullPointerException if list is null
25 protected static final @NonNull Object maskList(final ImmutableList<?> list) {
26 // Note: ImmutableList guarantees non-null content
27 return list.size() == 1 ? list.get(0) : list;
31 * Utility method for recovering singleton lists squashed by {@link #maskList(ImmutableList)}.
33 * @param masked list to unmask
34 * @return Unmasked list
35 * @throws NullPointerException if any argument is null
36 * @throws ClassCastException if masked object does not match expected class
38 @SuppressWarnings("unchecked")
39 protected static final <T> @NonNull ImmutableList<T> unmaskList(final @NonNull Object masked,
40 final @NonNull Class<T> type) {
41 return masked instanceof ImmutableList ? (ImmutableList<T>) masked
42 // Yes, this is ugly code, which could use an explicit verify, that would just change the what sort
43 // of exception we throw. ClassCastException is as good as VerifyException.
44 : ImmutableList.of(type.cast(masked));