import static java.util.Objects.requireNonNull;
-import com.google.common.annotations.Beta;
import com.google.common.collect.Iterators;
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;
+import java.util.SequencedSet;
import java.util.Set;
import java.util.Spliterator;
import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.yangtools.concepts.Immutable;
/**
- * A {@link Set} containing a single value. For some reason neither Java nor Guava provide direct access to the retained
- * element -- which is desirable in some situations, as is the case in {@link SharedSingletonMap#entrySet()}.
+ * A {@link SequencedSet} containing a single value. For some reason neither Java nor Guava provide direct access to the
+ * retained element -- which is desirable in some situations, as is the case in {@link SharedSingletonMap#entrySet()}.
*/
-@Beta
-public abstract class SingletonSet<E> implements Set<E>, Immutable, Serializable {
+public abstract sealed class SingletonSet<E> implements SequencedSet<E>, Immutable, Serializable {
+ @java.io.Serial
private static final long serialVersionUID = 1L;
- private static final SingletonSet<?> NULL_SINGLETON = new SingletonSet<>() {
- private static final long serialVersionUID = 1L;
-
- @Override
- @SuppressWarnings("checkstyle:parameterName")
- public boolean contains(final Object o) {
- return o == null;
- }
-
- @Override
- @SuppressWarnings("checkstyle:equalsHashCode")
- public int hashCode() {
- return 0;
- }
-
- @Override
- public @Nullable Object getElement() {
- return null;
- }
-
- @Override
- public @NonNull Spliterator<Object> spliterator() {
- return SingletonSpliterators.immutableOfNull();
- }
-
- @Override
- public @NonNull String toString() {
- return "[null]";
- }
-
- private Object readResolve() {
- return NULL_SINGLETON;
- }
- };
-
@SuppressWarnings("unchecked")
public static <E> @NonNull SingletonSet<E> of(final @Nullable E element) {
- return element == null ? (SingletonSet<E>) NULL_SINGLETON : new RegularSingletonSet<>(element);
+ return element == null ? (SingletonSet<E>) NullElement.INSTANCE : new Regular<>(element);
}
/**
* Return the single element contained in this set.
*
* @return This set's element.
+ * @deprecated Use {@link #getFirst()} instead.
*/
- public abstract E getElement();
+ @Deprecated(since = "14.0.0", forRemoval = true)
+ public final E getElement() {
+ return getFirst();
+ }
+
+ @Override
+ public abstract E getFirst();
+
+ @Override
+ public final E getLast() {
+ return getFirst();
+ }
+
+ @Override
+ public final SingletonSet<E> reversed() {
+ return this;
+ }
@Override
public final int size() {
@Override
public final @NonNull Iterator<E> iterator() {
- return Iterators.singletonIterator(getElement());
+ return Iterators.singletonIterator(getFirst());
}
@Override
@Override
public final @NonNull Object[] toArray() {
- return new Object[] { getElement() };
+ return new Object[] { getFirst() };
}
@SuppressWarnings({ "unchecked", "checkstyle:parameterName" })
@Override
public final <T> @NonNull T[] toArray(final T[] a) {
if (a.length > 0) {
- a[0] = (T)getElement();
+ a[0] = (T)getFirst();
return a;
}
- return (T[]) new Object[] {getElement()};
+ return (T[]) new Object[] { getFirst() };
}
@Override
throw new UnsupportedOperationException();
}
+ @Override
+ public final E removeFirst() {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public final E removeLast() {
+ throw new UnsupportedOperationException();
+ }
+
@Override
public final void clear() {
throw new UnsupportedOperationException();
@Override
@SuppressWarnings("checkstyle:equalsHashCode")
public final boolean equals(final Object obj) {
- if (obj == this) {
- return true;
- }
- if (!(obj instanceof Set)) {
- return false;
- }
+ return obj == this || obj instanceof Set<?> other && other.size() == 1 && otherContains(other);
+ }
- final Set<?> s = (Set<?>)obj;
- return s.size() == 1 && otherContains(s);
+ @java.io.Serial
+ final Object writeReplace() {
+ return new SSv1(getFirst());
}
+ @SuppressFBWarnings(value = "DCN_NULLPOINTER_EXCEPTION",
+ justification = "https://github.com/spotbugs/spotbugs/issues/1954")
private boolean otherContains(final @NonNull Collection<?> other) {
try {
- return other.contains(getElement());
+ return other.contains(getFirst());
} catch (ClassCastException | NullPointerException e) {
return false;
}
}
+ private static final class NullElement<E> extends SingletonSet<E> {
+ @java.io.Serial
+ private static final long serialVersionUID = 1L;
+ static final @NonNull NullElement<?> INSTANCE = new NullElement<>();
+
+ @Override
+ @SuppressWarnings("checkstyle:parameterName")
+ public boolean contains(final Object o) {
+ return o == null;
+ }
+
+ @Override
+ @SuppressWarnings("checkstyle:equalsHashCode")
+ public int hashCode() {
+ return 0;
+ }
+
+ @Override
+ public E getFirst() {
+ return null;
+ }
+
+ @Override
+ public Spliterator<E> spliterator() {
+ return SingletonSpliterators.immutableOfNull();
+ }
+
+ @Override
+ public String toString() {
+ return "[null]";
+ }
+ }
+
@NonNullByDefault
- private static final class RegularSingletonSet<E> extends SingletonSet<E> {
+ private static final class Regular<E> extends SingletonSet<E> {
+ @java.io.Serial
private static final long serialVersionUID = 1L;
- private final E element;
+ private final @NonNull E element;
- RegularSingletonSet(final E element) {
+ Regular(final E element) {
this.element = requireNonNull(element);
}
}
@Override
- public E getElement() {
+ public @NonNull E getFirst() {
return element;
}
@Override
@SuppressWarnings("checkstyle:equalsHashCode")
public int hashCode() {
- return getElement().hashCode();
+ return element.hashCode();
}
@Override
Code Review / yangtools.git / blobdiff