/** clamps index to [0..treeSize()] and inserts object o *before* the specified index */
public final synchronized void insertNode(int index, Object o) {
if(o == null) throw new Error("can't insert nulls in the balanced tree");
/** clamps index to [0..treeSize()] and inserts object o *before* the specified index */
public final synchronized void insertNode(int index, Object o) {
if(o == null) throw new Error("can't insert nulls in the balanced tree");