Inner Classes For Tree
Just a trick:) Not static inner classes give the opportunity elegantly implement Tree structure.
Example (only immutable code is shown):
interface INode
{
INode getParentNode();
Collection getChildrenNodes();
Data getSomeNodeData();
}
class DefaultNode implements INode
{
// members, initialization and mutable code has been omited
private class InnerNode extends DefaultNode
{
public INode getParentNode()
{
return DefaultNode.this;// outer class
}
}
public INode getParentNode()
{
return null;// or INode.ROOT if you use NULL object pattern...
}
public Collection getChildrenNodes()
{
return childrenNodes;// returns the Collection of InnerNodes
}
public Data getSomeNodeData()
{
return data;
}
}