SimpleCache.java

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 * Copyright (c) 2004, 2013 Steve Flasby
 * All rights reserved.
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 * are permitted provided that the following conditions are met:
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package org.flasby.util;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * is a simple cache which looks-up values if the key has no entry.<br>
 * It is not very smart and does not handle simultaneous requests from
 * multiple threads well as it will request the value multiple times.<br>
 * There is no cache expiry support either.<p>
 * 
 * For a smarter cache check ShinyCache instead.
 * 
 * @author steve
 *
 * @param <Key>
 * @param <Value>
 */
public abstract class SimpleCache<Key, Value> implements Cache<Key, Value> {
	
	private ConcurrentMap<Key, Value> mData = new ConcurrentHashMap<Key, Value>();

	protected abstract boolean matches( Value data, Key key );
	protected abstract Value create(Key key);

	@Override
	public Value get(Key key) {
		return mData.computeIfAbsent(key, this::create);
	}
	
	public List<Value> searchByKey(Key key) {
		List<Value> ret = new LinkedList<Value>();
		for (Value data : mData.values()) {
			if ( matches(data, key) ) {
				ret.add(data);
			}
		}
		return ret;
	}
	
	@Override
	public int size() {
		return mData.size();
	}
	
	@Override
	public Iterator<Value> iterator() {
		return mData.values().iterator();
	}


}