net.sf.ehcache.store.CacheKeySet Maven / Gradle / Ivy
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Ehcache is an open source, standards-based cache used to boost performance,
offload the database and simplify scalability. Ehcache is robust, proven and full-featured and
this has made it the most widely-used Java-based cache.
/**
* Copyright Terracotta, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package net.sf.ehcache.store;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
/**
* A Set of keys that will encapsulate keys present in a Cache.
* It will mostly behave as an immutable {@link java.util.Set}, but for its {@link #size} method
*
* @param the type of elements maintained by this set
* @author Alex Snaps
*/
public class CacheKeySet implements Set {
private static final Iterator EMPTY_ITERATOR = new Iterator() {
public boolean hasNext() {
return false;
}
public Object next() {
throw new UnsupportedOperationException();
}
public void remove() {
throw new UnsupportedOperationException();
}
};
private final Collection[] keySets;
/**
* Create a new Set for all tiers in the cache.
* Generally, you'd pass the authority's keySet, and higher layer pinned keySets
*
* @param keySets an array of keySets
*/
public CacheKeySet(final Collection... keySets) {
this.keySets = keySets;
}
/**
* Sums the size of all sets wrapped by this one, so this will not account for duplicated keys. Like for in-memory pinned keys, that
* might also present in lower tiers: e.g. DiskStore when its capacity isn't reached.
* @return the sum of all keySet sizes
*/
public int size() {
int size = 0;
for (Collection keySet : keySets) {
size += keySet.size();
}
return size;
}
/**
* {@inheritDoc}
*/
public boolean isEmpty() {
for (Collection keySet : keySets) {
if (!keySet.isEmpty()) {
return false;
}
}
return true;
}
/**
* {@inheritDoc}
*/
public boolean contains(final Object o) {
for (Collection keySet : keySets) {
if (keySet.contains(o)) {
return true;
}
}
return false;
}
/**
* {@inheritDoc}
*/
public Iterator iterator() {
return new KeySetIterator();
}
/**
* {@inheritDoc}
*/
public Object[] toArray() {
List list = new ArrayList();
for (E e : this) {
list.add(e);
}
return list.toArray();
}
/**
* {@inheritDoc}
*/
public T[] toArray(final T[] a) {
List list = new ArrayList();
for (E e : this) {
list.add(e);
}
return list.toArray(a);
}
/**
* You can't add to this set, will throw!
* @throws UnsupportedOperationException
*/
public boolean add(final Object o) {
throw new UnsupportedOperationException();
}
/**
* You can't remove from this set, will throw!
* @throws UnsupportedOperationException
*/
public boolean remove(final Object o) {
throw new UnsupportedOperationException();
}
/**
* {@inheritDoc}
*/
public boolean containsAll(final Collection c) {
for (Object o : c) {
if (!contains(o)) {
return false;
}
}
return true;
}
/**
* You can't add to this set, will throw!
* @throws UnsupportedOperationException
*/
public boolean addAll(final Collection c) {
throw new UnsupportedOperationException();
}
/**
* You can't remove from this set, will throw!
* @throws UnsupportedOperationException
*/
public boolean removeAll(final Collection c) {
throw new UnsupportedOperationException();
}
/**
* You can't remove from this set, will throw!
* @throws UnsupportedOperationException
*/
public boolean retainAll(final Collection c) {
throw new UnsupportedOperationException();
}
/**
* You can't remove from this set, will throw!
* @throws UnsupportedOperationException
*/
public void clear() {
throw new UnsupportedOperationException();
}
/**
* An iterator that will iterate over all keySets, avoiding duplicate entries
*/
private final class KeySetIterator implements Iterator {
private Iterator currentIterator;
private int index = 0;
private E next;
private E current;
private KeySetIterator() {
if (keySets.length == 0) {
this.currentIterator = EMPTY_ITERATOR;
} else {
this.currentIterator = keySets[0].iterator();
}
advance();
}
/**
* {@inheritDoc}
*/
public boolean hasNext() {
return next != null;
}
/**
* {@inheritDoc}
*/
public E next() {
current = next;
advance();
return current;
}
private void advance() {
next = null;
while (next == null) {
if (currentIterator.hasNext()) {
next = currentIterator.next();
for (int i = 0; i < index; i++) {
if (keySets[i].contains(next)) {
next = null;
}
}
} else {
next = null;
if (++index < keySets.length) {
currentIterator = keySets[index].iterator();
} else {
return;
}
}
}
}
/**
* {@inheritDoc}
*/
public void remove() {
throw new UnsupportedOperationException();
}
}
}