org.javimmutable.collections.util.MutableMapAdaptor Maven / Gradle / Ivy
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package org.javimmutable.collections.util;
import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.JImmutableMap;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* When converting legacy code to use JImmutableMap there are sometimes objects that shared the mutable
* version of their internal Map field with other classes. This class serves as an adaptor to allow
* this sharing to continue for a time after converting to JImmutableMap. However the legacy code should
* still be changed over time to eliminate the sharing of a mutable Map.
*
* Since a JImmutableMap has to be replaced to reflect any changes to the map it can be difficult to
* adapt one of them into a mutable Map. Concrete classes derived from this class only have to implement
* two methods, accessMap() and replaceMap() in order to implement the adaptor.
*
* NOTE: this adaptor is NOT thread safe. Do not use it in a multi-threaded environment.
*/
public abstract class MutableMapAdaptor
extends AbstractMap
{
private final Set> entries;
protected MutableMapAdaptor()
{
this.entries = new MutableEntrySet();
}
/**
* Implemented by derived classes to allow this adaptor to access their JImmutableMap instance.
*
* @return
*/
protected abstract JImmutableMap accessMap();
/**
* Implemented by derived classes to allow this adaptor to replace their JImmutableMap instance.
*
* @return
*/
protected abstract void replaceMap(JImmutableMap newMap);
@Override
public Set> entrySet()
{
return this.entries;
}
@Override
public V put(K key,
V value)
{
V oldValue = accessMap().get(key);
replaceMap(accessMap().assign(key, value));
return oldValue;
}
private class MutableEntrySet
extends AbstractSet>
{
@Override
public Iterator> iterator()
{
return new MutableEntryIterator();
}
@Override
public int size()
{
return accessMap().size();
}
@Override
public boolean add(Entry newEntry)
{
replaceMap(accessMap().assign(newEntry.getKey(), newEntry.getValue()));
return true;
}
@SuppressWarnings("unchecked")
@Override
public boolean remove(Object o)
{
final Map.Entry entry = (Entry)o;
final K key = entry.getKey();
if (accessMap().findEntry(key).isFilled()) {
replaceMap(accessMap().delete(key));
return true;
} else {
return false;
}
}
@SuppressWarnings("unchecked")
@Override
public boolean contains(Object o)
{
final Map.Entry entry = (Entry)o;
final K key = entry.getKey();
return (accessMap().find(key).isFilled());
}
@Override
public void clear()
{
replaceMap(accessMap().deleteAll());
}
}
private class MutableEntryIterator
implements Iterator>
{
private JImmutableMap startingMap;
private Cursor> current;
private Cursor> next;
private MutableEntryIterator()
{
startingMap = accessMap();
current = startingMap.cursor();
next = current.next();
}
@Override
public boolean hasNext()
{
if (accessMap() != startingMap) {
throw new ConcurrentModificationException();
}
return next.hasValue();
}
@Override
public Entry next()
{
if (accessMap() != startingMap) {
throw new ConcurrentModificationException();
}
try {
current = next;
next = next.next();
return new MutableMapEntry(current.getValue());
} catch (Cursor.NoValueException ignored) {
throw new NoSuchElementException();
}
}
@Override
public void remove()
{
if (accessMap() != startingMap) {
throw new ConcurrentModificationException();
}
final K key = current.getValue().getKey();
replaceMap(accessMap().delete(key));
startingMap = accessMap();
}
private class MutableMapEntry
extends AbstractMap.SimpleEntry
{
private MutableMapEntry(JImmutableMap.Entry entry)
{
super(entry.getKey(), entry.getValue());
}
@Override
public V setValue(V newValue)
{
if (accessMap() != startingMap) {
throw new ConcurrentModificationException();
}
replaceMap(accessMap().assign(getKey(), newValue));
V answer = super.setValue(newValue);
startingMap = accessMap();
return answer;
}
}
}
}