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jStyleParser is a CSS parser written in Java. It has its own application interface that is designed to allow an efficient CSS processing in Java and mapping the values to the Java data types. It parses CSS 2.1 style sheets into structures that can be efficiently assigned to DOM elements. It is intended be the primary CSS parser for the CSSBox library. While handling errors, it is user agent conforming according to the CSS specification.

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/**
 * 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);
    }
    
}