src/main/java/com/workplacesystems/utilsj/collections/helpers/CollectionUtilities.java
public static <K,V> void reverse(Map<K,V> source, Map<V,K> target)
    {
        Iterator<K> i = source.keySet().iterator();
        while (i.hasNext())
        {
            K key = i.next();
            V value = source.get(key);
            target.put(value, key);
        }
    }
public static <K,V> void reverse(Map<K,V> source, Map<V,K> target)
    {
        Iterator<K> i = source.keySet().iterator();
        while (i.hasNext())
        {
            K key = i.next();
            V value = source.get(key);
            target.put(value, key);
        }
    }
Take key and value pairs from source and create map from value to key in target.