OrderedMap.java :  » Web-Server » jo » com » tagtraum » framework » util » Java Open Source

package com.tagtraum.framework.util;

import java.util.*;

/**
 * Map that maintains insertion order.
 * Does not properly deal with null keys.
 *
 * @version 1.1beta1, Revision: $id: $
 * @author <a href="mailto:hs@tagtraum.com">Hendrik Schreiber</a>
 */
public class OrderedMap {

    private Map map;
    private List list;

    public OrderedMap() {
        this.map = new HashMap();
        this.list = new ArrayList();
    }

    public boolean containsKey(Object key) {
        return map.containsKey(key);
    }

    /**
     * This method does NOT return a set that maintains the insertion order.
     */
    public Set keySet() {
        return Collections.unmodifiableSet(map.keySet());
    }

    public Object put(Object key, Object value) {
        Object oldValue = map.put(key, value);
        if (oldValue != null) {
            // find the right element
            Entry oldEntry = new Entry(key, oldValue);
            int i= list.indexOf(oldEntry);
            Entry e = (Entry)list.get(i);
            e.setIntValue(value);
        }
        else {
            list.add(new Entry(key, value));
        }
        return oldValue;
    }

    public Object remove(Object key) {
        Object oldValue = map.remove(key);
        if (oldValue != null) list.remove(new Entry(key, oldValue));
        return oldValue;
    }

    public Object get(Object key) {
        return map.get(key);
    }

    public void clear() {
        map.clear();
        list.clear();
    }

    public boolean isEmpty() {
        return map.isEmpty();
    }

    public List entryList() {
        return Collections.unmodifiableList(list);
    }

    public int size() {
        return map.size();
    }

    private class Entry implements Map.Entry {
        private Object key;
        private Object value;

        public Entry(Object key, Object value) {
            this.key = key;
            this.value = value;
        }

        public Object getKey() {
            return key;
        }

        public Object getValue() {
            return value;
        }

        void setIntValue(Object value) {
            this.value = value;
        }

        public Object setValue(Object value) {
            throw new UnsupportedOperationException();
        }

        public boolean equals(Object o) {
            if (!(o instanceof Map.Entry)) return false;
            Map.Entry e = (Map.Entry)o;
            Object k1 = getKey();
            Object k2 = e.getKey();
            if (k1 == k2 || (k1 != null && k1.equals(k2))) {
                Object v1 = getValue();
                Object v2 = e.getValue();
                if (v1 == v2 || (v1 != null && v1.equals(v2)))
                    return true;
            }
            return false;
        }

        public int hashCode() {
            return (key.hashCode()) ^ (value==null   ? 0 : value.hashCode());
        }

        public String toString() {
            return getKey() + "=" + getValue();
        }
    }

}