java - stealing bits from references

How do I steal 2 MSBs from an address to do an atomic operation? I'm trying to do a single word CAS

An example

public class Node
{
    long key;
    long value;
    Node lchild; // format is flag1,flag2,address
    Node rchild; // format is flag1,flag2,address
}

public void createNode()
{
    Node n1 = new Node(); //this should create a node with format 0,0,address1
}

public void setFlag1(Node n1)
{
    Now the new address should be in format 1,0,address1
}

public void setFlag2(Node n1)
{
    Now the new address should be in format 0,1,address1
}

AtomicReference could be used if I needed only one extra flag. AtomicStampedReference could be used but it is not efficient as it creates an extra box containing timeStamp and a reference.

A similar problem in C is discussed in stealing bits from a pointer