Java/Abstract Classes

Example: defining an abstract Tree type that implements abstract methods for some of the methods required by the Tree ADT:

• element()
• root()
• is_root
• parent
• num_children
• is_leaf

public abstract class Tree {
   abstract Node root();
  abstract Node parent(Node n);
  abstract int num_children(Node n);
  abstract Node children(Node n);
  abstract boolean is_leaf(Node n);
  abstract int length();
  abstract boolean isEmpty();
  // positions() - iteration of all Nodes in the tree
  // iter() - iteration of all elements in the tree
}