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javadata-structuresdecoratorcomposite

Copying complex data structures in Java

I am using Composite pattern in my Java program, such that a Component is being extended by three classes.

  1. Leaf class extends Component
  2. Composite extends Component
  3. Decorator extends Component (for decorating leafs)

The composite is currently implemented using a List, where each element can either be a leaf, another Composite or a decorator. I am thinking of adding undo/redo functionality for which I am going to be using Command/Memento patterns.

Now my question, how can I create a deep copy of my list here, so that I can restore it later? Basically, need to find a way that allows me to create a new identical copy of my list at the current time before executing another command. I am thinking there has to be some recursive way of doing it.

Thanks

Solution

  • The cheapest approach to code (but perhaps not the cheapest in terms of the overall CPU and memory use) is to mark your classes serializable, serialize the list into a memory buffer, and then deserialize it back into an object. If you do it right, the result is going to be a deep copy of your list of objects.