cz.vutbr.web.domassign.MultiMap Maven / Gradle / Ivy
/**
* MultiMap.java
*
* Created on 31.1.2010, 21:20:00 by radek
*/
package cz.vutbr.web.domassign;
import java.util.Collections;
import java.util.HashMap;
import java.util.Set;
/**
* This is a general map that assigns the data D to two keys E (Element) and P (Pseudo element).
* The element is mandatory, the PseudoElement key value may be null. When P is null, the structure
* behaves as a simple map called a main map. Other values of PseudoElement create so-called pseudo
* maps. The map is optimized to provide the best performance for the main map.
*
* @author burgetr
*/
public abstract class MultiMap
{
private HashMap mainMap; //main map for no pseudo-elements
private HashMap> pseudoMaps; //maps for the individual pseudo-elements
/**
* Creates an empty map
*/
public MultiMap()
{
mainMap = new HashMap();
pseudoMaps = new HashMap>();
}
/**
* Creates an empty map
*/
public MultiMap(int initialSize)
{
mainMap = new HashMap(initialSize);
pseudoMaps = new HashMap>();
}
/**
* Creates a new instance of the data value.
* This is only used by {@link MultiMap#getOrCreate(Object, Object)}.
*/
protected abstract D createDataInstance();
/**
* Obtains the size of the main map (where P is null)
* @return the number of elements in the main map.
*/
public int size()
{
return mainMap.size();
}
/**
* Gets the data for the given element and pseudo-element.
* @param el the element
* @param pseudo a pseudo-element or null, if no pseudo-element is required
* @return the stored data
*/
public D get(E el, P pseudo)
{
D ret;
if (pseudo == null)
ret = mainMap.get(el);
else
{
HashMap map = pseudoMaps.get(el);
if (map == null)
ret = null;
else
ret = map.get(pseudo);
}
return ret;
}
/**
* Gets the data for the given element and no pseudo-element
* @param el the element
* @return the stored data
*/
public D get(E el)
{
return mainMap.get(el);
}
/**
* Gets the data or creates an empty list if it does not exist yet.
* @param el the element
* @param pseudo a pseudo-element or null, if no pseudo-element is required
* @return the stored data
*/
public D getOrCreate(E el, P pseudo)
{
D ret;
if (pseudo == null)
{
ret = mainMap.get(el);
if (ret == null)
{
ret = createDataInstance();
mainMap.put(el, ret);
}
}
else
{
HashMap map = pseudoMaps.get(el);
if (map == null)
{
map = new HashMap();
pseudoMaps.put(el, map);
}
ret = map.get(pseudo);
if (ret == null)
{
ret = createDataInstance();
map.put(pseudo, ret);
}
}
return ret;
}
/**
* Sets the data for the specified element and pseudo-element.
* @param el the element to which the data belongs
* @param pseudo a pseudo-element or null of none is required
* @param data data to be set
*/
public void put(E el, P pseudo, D data)
{
if (pseudo == null)
mainMap.put(el, data);
else
{
HashMap map = pseudoMaps.get(el);
if (map == null)
{
map = new HashMap();
pseudoMaps.put(el, map);
}
map.put(pseudo, data);
}
}
/**
* Gets all the keys (elements) of the main map.
* @return A set of elements contained in the map.
*/
public Set keySet()
{
return mainMap.keySet();
}
/**
* Gets all the pseudo elements that are available for the given element.
* @param el The given element
* @return A set of all pseudo elements available for the element
*/
public Set pseudoSet(E el)
{
HashMap map = pseudoMaps.get(el);
if (map == null)
return Collections.emptySet();
else
return map.keySet();
}
/**
* Checks if the given pseudo element is available for the given element
* @param el The element
* @param pseudo The tested pseudo element
* @return true when there is some value associated with the given pair
*/
public boolean hasPseudo(E el, P pseudo)
{
HashMap map = pseudoMaps.get(el);
if (map == null)
return false;
else
return map.containsKey(pseudo);
}
}