in commons/src/main/java/org/apache/causeway/commons/collections/Can_Empty.java [49:347]
record Can_Empty<T>() implements Can<T> {
static final Can_Empty<?> INSTANCE = new Can_Empty<>();
@Override
public Cardinality getCardinality() {
return Cardinality.ZERO;
}
@Override
public Stream<T> stream() {
return Stream.empty();
}
@Override
public Stream<T> parallelStream() {
return Stream.empty();
}
@Override
public Optional<T> getSingleton() {
return Optional.empty();
}
@Override
public Optional<T> getFirst() {
return Optional.empty();
}
@Override
public Optional<T> getLast() {
return Optional.empty();
}
@Override
public Optional<T> get(final int elementIndex) {
return Optional.empty();
}
@Override
public boolean contains(final @Nullable T element) {
return false;
}
@Override
public int size() {
return 0;
}
@Override
public Iterator<T> iterator(final int skip, final int limit) {
return iterator(); // empty iterator no matter what the arguments
}
@Override
public Iterator<T> iterator() {
return Collections.<T>emptyList().iterator();
}
@Override
public Can<T> sorted(final @NonNull Comparator<? super T> c) {
return this;
}
@Override
public Can<T> distinct() {
return this;
}
@Override
public Can<T> distinct(final @NonNull BiPredicate<T, T> equality) {
return this;
}
@Override
public Can<T> reverse() {
return this;
}
@Override
public Iterator<T> reverseIterator() {
return iterator();
}
@Override
public Can<T> reduce(final @NonNull BinaryOperator<T> accumulator) {
return this; // reduction of empty yields empty
}
@Override
public void forEach(final Consumer<? super T> action) {
}
@Override
public Can<T> filter(final @Nullable Predicate<? super T> predicate) {
return this; // identity
}
@Override
public <R> void zip(final Iterable<R> zippedIn, final BiConsumer<? super T, ? super R> action) {
// no-op
}
@Override
public <R, Z> Can<R> zipMap(final Iterable<Z> zippedIn, final BiFunction<? super T, ? super Z, R> mapper) {
return Can.empty();
}
@Override
public <R, Z> Stream<R> zipStream(final Iterable<Z> zippedIn, final BiFunction<? super T, ? super Z, R> mapper) {
return Stream.empty();
}
@Override
public Can<T> add(final @Nullable T element) {
return element != null
? Can.ofSingleton(element)
: this;
}
@Override
public Can<T> addUnique(final @Nullable T element) {
return add(element);
}
@Override
public Can<T> addAll(final @Nullable Can<T> other) {
return other != null
? other
: this;
}
@Override
public Can<T> add(final int index, final @Nullable T element) {
if(index!=0) {
throw new IndexOutOfBoundsException(
"cannot add to empty can with index other than 0; got " + index);
}
return add(element);
}
@Override
public Can<T> replace(final int index, final @Nullable T element) {
throw _Exceptions.unsupportedOperation("cannot replace an element in an empty Can");
}
@Override
public Can<T> remove(final int index) {
throw new IndexOutOfBoundsException("cannot remove anything from an empty Can");
}
@Override
public Can<T> remove(final @Nullable T element) {
return this; // on an empty can this is a no-op
}
@Override
public Can<T> pickByIndex(final @Nullable int... indices) {
return Can.empty();
}
@Override
public Can<T> pickByIndex(final @Nullable IntStream intStream) {
return Can.empty();
}
@Override
public Can<T> subCan(final int startInclusive) {
return Can.empty();
}
@Override
public Can<T> subCan(final int startInclusive, final int endExclusive) {
return Can.empty();
}
@Override
public Can<Can<T>> partitionInnerBound(final int maxInnerSize) {
return Can.empty();
}
@Override
public Can<Can<T>> partitionOuterBound(final int outerSizeYield) {
return Can.empty();
}
@Override
public int indexOf(final @Nullable T element) {
return -1;
}
@Override
public boolean anyMatch(final Predicate<? super T> predicate) {
return false;
}
@Override
public boolean allMatch(final Predicate<? super T> predicate) {
return true;
}
@Override
public String toString() {
return "Can[]";
}
@Override
public boolean equals(final @Nullable Object obj) {
if(INSTANCE == obj) {
return true; // optimization not strictly necessary
}
return (obj instanceof Can)
? ((Can<?>)obj).isEmpty()
: false;
}
@Override
public int hashCode() {
return 0;
}
@Override
public int compareTo(final @Nullable Can<T> other) {
if(other==null) {
return 0;
}
// when returning
// -1 ... this is before other
// +1 ... this is after other
return Integer.compare(0, other.size()); // all empty Cans are same and come first
}
@Override
public List<T> toList() {
return Collections.emptyList(); // serializable and immutable
}
@Override
public List<T> toArrayList() {
return _Lists.newArrayList();
}
@Override
public Set<T> toSet() {
return Collections.emptySet(); // serializable and immutable
}
@Override
public Set<T> toSet(final @NonNull Consumer<T> onDuplicated) {
return Collections.emptySet(); // serializable and immutable
}
@Override
public T[] toArray(final @NonNull Class<T> elementType) {
var array = _Casts.<T[]>uncheckedCast(Array.newInstance(elementType, 0));
return array;
}
@Override
public <K> Map<K, T> toMap(
final @NonNull Function<? super T, ? extends K> keyExtractor) {
return Collections.emptyMap();
}
@Override
public <K, M extends Map<K, T>> Map<K, T> toMap(
final @NonNull Function<? super T, ? extends K> keyExtractor,
final @NonNull BinaryOperator<T> mergeFunction,
final @NonNull Supplier<M> mapFactory) {
return Collections.emptyMap();
}
@Override
public <R, A> R collect(final @NonNull Collector<? super T, A, R> collector) {
return collector.finisher().apply(collector.supplier().get());
}
@Override
public <K> Map<K, Can<T>> groupBy(
final @NonNull Function<? super T, ? extends K> classifier) {
return Collections.emptyMap();
}
@Override
public <K, M extends Map<K, Can<T>>> Map<K, Can<T>> groupBy(
final @NonNull Function<? super T, ? extends K> classifier,
final @NonNull Supplier<M> mapFactory) {
return Collections.emptyMap();
}
@Override
public String join(final @NonNull String delimiter) {
return "";
}
@Override
public String join(final @NonNull Function<? super T, String> toStringFunction, final @NonNull String delimiter) {
return "";
}
}