preOrderEnumeration(): The first node is the node itself. The next node is that node's first child, then it's the first child of that first child. Once a leaf node with no children is found, the next child of its parent is put in the Enumeration and its children are added to the list accordingly until no nodes are left.
depthFirstEnumeration() and postOrderEnumeration(): Return an Enumeration that has practically the opposite behavior of preOrderEnumeration(). Instead of including the current node first and then adding the children, these methods add the children first and then add the current node to the Enumeration.
breadthFirstEnumeration(): Returns an Enumeration of nodes added by level.
import java.awt.BorderLayout;
import java.util.Enumeration;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreeNode;
publicclass PostPreorderAndDepthEnumeration {
publicstaticvoid main(String args[]) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
DefaultMutableTreeNode mercury = new DefaultMutableTreeNode("Mercury");
root.add(mercury);
DefaultMutableTreeNode venus = new DefaultMutableTreeNode("Venus");
root.add(venus);
DefaultMutableTreeNode mars = new DefaultMutableTreeNode("Mars");
root.add(mars);
JTree tree = new JTree(root);
JScrollPane scrollPane = new JScrollPane(tree);
frame.add(scrollPane, BorderLayout.CENTER);
frame.setSize(300, 150);
frame.setVisible(true);
Enumeration e = root.preorderEnumeration();
while(e.hasMoreElements()){
System.out.println(e.nextElement());
}
e = root.postorderEnumeration();
while(e.hasMoreElements()){
System.out.println(e.nextElement());
}
e = root.depthFirstEnumeration();
while(e.hasMoreElements()){
System.out.println(e.nextElement());
}
}
}
