Helper class to transform values in map

MapTransformer.java

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class MapTransformer<K, V>
{
	private Transformation<K> keyTransformation;
	private Transformation<V> valueTransformer;
	
	public MapTransformer(Transformation<K> keyTransformation, Transformation<V> valueTransformer)
	{
		this.keyTransformation = keyTransformation;
		this.valueTransformer = valueTransformer;
	}
	
	// Assumes transformed is empty
	public void transform(Map<K, V> original, Map<K, V> transformed)
	{
		Set<Map.Entry<K, V>> entrySet = original.entrySet();
		
		for (Map.Entry<K, V> entry : entrySet)
		{
			transformed.put(keyTransformation.callback(entry.getKey()), valueTransformer.callback(entry.getValue()));
		}
	}
	
	public Map<K,V> transform(Map<K, V> original)
	{
		Map<K, V> transformedMap = new HashMap<K, V>();
		this.transform(original, transformedMap);
		
		return transformedMap;
	}
	
	public void transformInPlace(Map<K, V> map)
	{
		Set<Map.Entry<K, V>> entrySet = map.entrySet();
		map.clear();
		
		for (Map.Entry<K, V> entry : entrySet)
		{
			map.put(keyTransformation.callback(entry.getKey()), valueTransformer.callback(entry.getValue()));
		}
	}
}

Transformation.java

public interface Transformation<T>
{
	public T callback(T val);
}