Mega Code Archive
History Map
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// $Id: HistoryMap.java,v 1.11 2003/09/11 12:33:06 larsga Exp $
//package net.ontopia.utils;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
//import org.slf4j.Logger;
//import org.slf4j.LoggerFactory;
/**
* INTERNAL: Helper class for storing elements up to a certain amount, lower
* most elements will be removed to ensure a fixed size of the collection.
*
* @since 1.2.5
*/
public class HistoryMap<T> extends HashMap<Integer, T> {
protected int maxEntries;
protected boolean suppressDuplicates;
private int counter;
// initialization of logging facility
// private static Logger log =
// LoggerFactory.getLogger(HistoryMap.class.getName());
/**
* Default constructor which uses 20 entries as the default history size and
* does suppress duplicates.
*/
public HistoryMap() {
this(20, true);
}
/**
* Constructor which allows to specify number of entries to store and
* duplicate suppression behaviour.
*
* @param maxEntries
* Maxium number of entries to store in the history.
* @param suppressDuplicates
* Should suppress duplicate entries in map.
*/
public HistoryMap(int maxEntries, boolean suppressDuplicates) {
super();
this.maxEntries = maxEntries;
this.counter = 0;
this.suppressDuplicates = suppressDuplicates;
}
public int getMaxEntries() {
return maxEntries;
}
public boolean doesSuppressDuplicates() {
return suppressDuplicates;
}
public void add(T obj) {
// do not add if object already exists
if (suppressDuplicates && containsValue(obj))
return;
counter++;
put(new Integer(counter), obj);
if (size() >= maxEntries)
try {
remove(new Integer(counter - maxEntries));
} catch (Exception e) {
// log.error("Remove of entry from historymap without success."
// +
// e.getMessage());
}
}
public void removeEntry(T obj) {
Iterator<Integer> it = keySet().iterator();
// log.info("A removing from history");
while (it.hasNext()) {
Integer key = it.next();
T val = get(key);
if (val.equals(obj)) {
// log.info("removing from history " + key);
remove(key);
break;
}
} // while it
}
public T getEntry(int index) {
return get(new Integer(counter - size() + index));
}
public Collection<T> getEntries() {
Collection<T> result = new ArrayList<T>();
for (int i = 1; i <= size(); i++) {
if (getEntry(i) != null)
result.add(getEntry(i));
}
return result;
}
public Collection getEntriesReverse() {
Collection result = new ArrayList();
for (int i = size(); i >= 1; i--) {
if (getEntry(i) != null)
result.add(getEntry(i));
}
return result;
}
}
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