public abstract class ObservableListBase<E> extends AbstractList<E> implements ObservableList<E>:

First of all, it will implement following ObservableList methods:

public final void addListener(InvalidationListener listener)
public final void removeListener(InvalidationListener listener)
public final void addListener(ListChangeListener<? super E> listener)
public final void removeListener(ListChangeListener<? super E> listener)

... and will contain these new methods:

// calls all the listeners of this ObservableList
protected final void fireChange(ListChangeListener.Change<E> change)
// true if there are some registered listeners
protected final boolean hasListeners()

protected final ListChangeBuilder<E> changeBuilder();

The ListChangeBuilder class will look like this:

public final void nextUpdate(int pos)
public final void nextSet(int idx, E old)
public final void nextReplace(int from, int to, ArrayList removed)
public final void nextRemove(int idx, List removed)
public final void nextRemove(int idx, E removed)
public final void nextPermutation(int from, int to, int[] perm)
public final void nextAdd(int from, int to)
public final void endChange()
public final void beginChange()

All next* methods need to be enclosed in beginChange() / endChange() pair. The calls can be also nested and after the outermost endChange() call, callListeners() will be called with the newly created Change.

public abstract class ModifiableObservableListBase<E> extends ObservableListBase<E>:

This class introduces three new abstract methods:

 protected abstract void doAdd(int index, E element);
 protected abstract E doSet(int index, E element);
 protected abstract E doRemove(int index);

These methods are meant to contain simple list manipulations. The ModifiableObservableListBase implementation takes care of Change construction (using ListChangeBuilder methods), but subclasses can override this behaviour.