org.eclipse.persistence.internal.oxm.VectorUtils Maven / Gradle / Ivy
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/*
* Copyright (c) 2020 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0,
* or the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
*/
package org.eclipse.persistence.internal.oxm;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Objects;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.Vector;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;
import static java.util.Collections.emptyIterator;
import static java.util.Collections.emptyListIterator;
/**
* This class provides "empty" and "unmodifiable" wrappers for the Vector class.
* The functionality is similar the Collections class and mostly copy-paste from the class.
* Unfortunately, the standard Collections class does not provides wrappers for the outdated Vector class.
*
* @see Collections
*/
public class VectorUtils {
/**
* The empty vector (immutable).
* @see #emptyVector()
*/
public static final Vector EMPTY_VECTOR = new EmptyVector();
/**
* Returns an unmodifiable view of the specified vector. This method allows
* modules to provide users with "read-only" access to internal
* vectors. Query operations on the returned vector "read through" to the
* specified vector, and attempts to modify the returned vector, whether
* direct or via its iterator, result in an
* UnsupportedOperationException.
*
* @param the class of the objects in the vector
* @param vector the vector for which an unmodifiable view is to be returned.
* @return an unmodifiable view of the specified vector.
*/
public static Vector unmodifiableVector(Vector vector) {
if (vector == null) {
throw new IllegalArgumentException("Input value must not be NULL!");
}
return new UnmodifiableVector<>(vector);
}
/**
* Returns an empty vector (immutable).
*
* This example illustrates the type-safe way to obtain an empty vector:
*
* Vector<String> s = VectorUtils.emptyVector();
*
* @param type of elements, if there were any, in the vector
* @return an empty immutable vector
* @implNote Implementations of this method need not create a separate Vector
* object for each call. Using this method is likely to have comparable
* cost to using the like-named field. (Unlike this method, the field does
* not provide type safety.)
* @see #EMPTY_VECTOR
*/
@SuppressWarnings("unchecked")
public static final Vector emptyVector() {
return (Vector) EMPTY_VECTOR;
}
private VectorUtils() {}
private static class EmptyVector extends Vector {
private static final long serialVersionUID = 5020332176914113951L;
@Override
public int size() {return 0;}
@Override
public boolean isEmpty() {return true;}
@Override
public boolean contains(Object obj) {return false;}
@Override
public Object[] toArray() { return new Object[0]; }
@Override
public T[] toArray(T[] a) {
if (a.length > 0) {
a[0] = null;
}
return a;
}
@Override
public E get(int index) {
throw new IndexOutOfBoundsException("Index: " + index);
}
@Override
public void add(int index, E element) {
throw new UnsupportedOperationException();
}
@Override
public boolean containsAll(Collection c) { return c.isEmpty(); }
@Override
public boolean equals(Object o) {
return (o instanceof Vector) && ((Vector) o).isEmpty();
}
@Override
public int hashCode() { return 1; }
@Override
public ListIterator listIterator(int index) {
return emptyListIterator();
}
@Override
public ListIterator listIterator() {
return emptyListIterator();
}
@Override
public Iterator iterator() {
return emptyIterator();
}
// Override default methods in Collection
@Override
public void forEach(Consumer action) {
Objects.requireNonNull(action);
}
@Override
public boolean removeIf(Predicate filter) {
Objects.requireNonNull(filter);
return false;
}
@Override
public void replaceAll(UnaryOperator operator) {
Objects.requireNonNull(operator);
}
@Override
public void sort(Comparator c) {
}
@Override
public Spliterator spliterator() { return Spliterators.emptySpliterator(); }
// Preserves singleton property
private Object readResolve() {
return EMPTY_VECTOR;
}
}
/**
* @serial include
*/
static class UnmodifiableVector extends Vector {
private static final long serialVersionUID = -8378199697360550972L;
UnmodifiableVector(Vector vector) {
super(vector);
}
public E set(int index, E element) {
throw new UnsupportedOperationException();
}
public void add(int index, E element) {
throw new UnsupportedOperationException();
}
public E remove(int index) {
throw new UnsupportedOperationException();
}
public boolean addAll(int index, Collection c) {
throw new UnsupportedOperationException();
}
@Override
public List subList(int fromIndex, int toIndex) {
return Collections.unmodifiableList(super.subList(fromIndex, toIndex));
}
public ListIterator listIterator(final int index) {
return new ListIterator() {
private final ListIterator i
= listIterator(index);
public boolean hasNext() {return i.hasNext();}
public E next() {return i.next();}
public boolean hasPrevious() {return i.hasPrevious();}
public E previous() {return i.previous();}
public int nextIndex() {return i.nextIndex();}
public int previousIndex() {return i.previousIndex();}
public void remove() {
throw new UnsupportedOperationException();
}
public void set(E e) {
throw new UnsupportedOperationException();
}
public void add(E e) {
throw new UnsupportedOperationException();
}
@Override
public void forEachRemaining(Consumer action) {
i.forEachRemaining(action);
}
};
}
public ListIterator listIterator() {return listIterator(0);}
@Override
public void replaceAll(UnaryOperator operator) {
throw new UnsupportedOperationException();
}
@Override
public void sort(Comparator c) {
throw new UnsupportedOperationException();
}
}
}