net.sf.jabb.util.col.AtomicComputeIfAbsentMap Maven / Gradle / Ivy

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/**
 * 
 */
package net.sf.jabb.util.col;

import java.io.Serializable;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Function;

/**
 * A wrapper of Map that always automatically do computeIfAbsent(...) within get(...).
 * The invocation of computeIfAbsent(...) within get(...) is performed atomically, 
 * so the function is applied at most once per key. 
 * 
 * Please note that only these methods are thread-safe if the underlying Map is not a ConcurrentMap: get/put/putAll/remove/clear
 * 
 * @author James Hu
 *
 */
public class AtomicComputeIfAbsentMap, K, V> implements Map, Serializable{
	private static final long serialVersionUID = 1420553680835327352L;

	protected M map;
	protected Function computeFunction;
	protected Object structureLock = new Object();

	
    /**
     * Creates a new map with the same mappings as the given map.
     *
     * @param m the map
     * @param computeFunction the function to compute a value when there is no value currently associated with the key
     */
	public AtomicComputeIfAbsentMap(M m, Function computeFunction){
		this.map = m;
		this.computeFunction = computeFunction;
	}
	
	public M getMap(){
		return map;
	}
	
	@Override
	public String toString(){
		return map.toString();
	}

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

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

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

	@Override
	public boolean containsValue(Object value) {
		return map.containsValue(value);
	}

	@SuppressWarnings("unchecked")
	@Override
	public V get(Object key) {
		V result;
		result = map.get(key);
		if (result == null){
			synchronized(structureLock){
				result = map.computeIfAbsent((K)key, computeFunction);
			}
		}
		return result;
	}

	@Override
	public V put(K key, V value) {
		synchronized(structureLock){
			return map.put(key, value);
		}
	}

	@Override
	public V remove(Object key) {
		synchronized(structureLock){
			return map.remove(key);
		}
	}

	@Override
	public void putAll(Map m) {
		synchronized(structureLock){
			map.putAll(m);
		}
	}

	@Override
	public void clear() {
		synchronized(structureLock){
			map.clear();
		}
	}

	@Override
	public Set keySet() {
		return map.keySet();
	}

	@Override
	public Collection values() {
		return map.values();
	}

	@Override
	public Set> entrySet() {
		return map.entrySet();
	}
	
	/////// overriding defaults //////////
	
	@Override
	public V getOrDefault(Object key, V defaultValue) {
		return map.getOrDefault(key, defaultValue);
	}
	
	@Override
	public void forEach(BiConsumer action) {
		map.forEach(action);
	}
	
	@Override
	public void replaceAll(BiFunction function) {
		map.replaceAll(function);
	}
	
	@Override
	public V putIfAbsent(K key, V value) {
		return map.putIfAbsent(key, value);
	}

	@Override
	public boolean remove(Object key, Object value) {
		return map.remove(key, value);
	}
	
	@Override
	public boolean replace(K key, V oldValue, V newValue) {
		return map.replace(key, oldValue, newValue);
	}
	
	@Override
	public V replace(K key, V value) {
		return map.replace(key, value);
	}
	
	@Override
	public V computeIfAbsent(K key,
            Function mappingFunction) {
		return map.computeIfAbsent(key, mappingFunction);
	}
	
	@Override
	public V computeIfPresent(K key,
            BiFunction remappingFunction) {
		return map.computeIfPresent(key, remappingFunction);
	}
	
	@Override
	public V compute(K key,
            BiFunction remappingFunction) {
		return map.compute(key, remappingFunction);
	}
	
	@Override
	public V merge(K key, V value,
            BiFunction remappingFunction) {
		return map.merge(key, value, remappingFunction);
	}
}