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package tim.prune.undo;
import java.util.Stack;
/**
* Class to hold an undo operation together with a counter
*/
class UndoOpWithState
{
public UndoOperation _undoOperation = null;
public int _undoCounter = 0;
/** Constructor */
public UndoOpWithState(UndoOperation inOp, int inCounter)
{
_undoOperation = inOp;
_undoCounter = inCounter;
}
}
/**
* Stack of undo operations
* which also remembers how many undos have been performed
*/
public class UndoStack extends Stack<UndoOpWithState>
{
/** Number of undos (and clears) already performed */
private int _numUndos = 0;
@Override
public void clear()
{
_numUndos++;
super.clear();
}
/** Add an undo operation to the stack */
public synchronized boolean add(UndoOperation inOp)
{
return super.add(new UndoOpWithState(inOp, _numUndos));
}
/** Pop the latest operation from the stack */
public synchronized UndoOperation popOperation()
{
_numUndos++;
return super.pop()._undoOperation;
}
/** Get the operation at the given index */
public UndoOperation getOperationAt(int inIndex)
{
return super.elementAt(inIndex)._undoOperation;
}
/** @return number of undos */
public int getNumUndos()
{
if (isEmpty()) {return 0;}
// Get the number of undos stored by the last operation on the stack
return peek()._undoCounter;
}
}
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