Generic class with Memory?

Question

This question has been edited from its original version

Hi everyone, following your comments, I have modified my original class. The objective of this class is to store two sets of values:

• The first one is the "applied" one. If the user request the data from the class, he will receive this one.
• The second one is the "pending" changes. If the user modify the data, it will be stored into this set.
• When the user apply the changes, they are copied in the first set.

Now, here is the class as I changed it:

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

public class ChangesQueue< K, V, T extends Map< K, V > > implements Serializable {

    private static final long serialVersionUID = 1L;

    HashMap< K, V > mCurrent;
    HashMap< K, V > mStack;

    public ChangesQueue() {
        mCurrent = new HashMap< K, V >();
        mStack   = new HashMap< K, V >();
    }

    public ChangesQueue(T iValue) {
        this();
        set(iValue);
        apply();
    }

    public void apply() {
        mCurrent = new HashMap< K, V >(mStack);
    }

    public Map< K, V > get() {
        return mCurrent;
    }

    public void set(T iValue) {
        mStack.putAll(iValue);
    }

}

The biggest issue that I have here is that I cannot actually store the real type of T, which is why I am instantiating 'HashMap'. But this class is not intended to work only with 'HashMap', but with any kind of maps.

Actually, I am using this memory with the following class:

public class IndexedHashMap<K, T> implements Map<K, Pair< Integer, T >>, Serializable

And accessing the data with the following method:

private IndexedHashMap<String, T> getElements()
{
    return (null != mElements.get()) ? (IndexedHashMap<String, T>) mElements.get() : new  IndexedHashMap<String, T>();
}

Of course this is not possible as the cast is not valid.

I am currently considering a simple extension of 'IndexedHashMap' but I would really need a sort of generic Memory (this is not a YAGNI case) and I do not want to get multiples, specific classes, for the same thing.

Would there be any way to do this while keeping the generic side ? Maybe it is achievable if I use a 'Class clazz' argument which would allow me to instantiate the real type of T instead of an HashMap ?

Thanks for the help