Trees CSCI 201 Principles of Software Development

Transcription

1 Trees CSCI 201 Principles of Software Development Jeffrey Miller, Ph.D.

2 Outline Trees Program USC CSCI 201L

3 Trees Overview JTree is a component that displays data in a treelike hierarchy All nodes displayed in the tree are in the form of a hierarchical indexed list A node can have child nodes A node with no children is a leaf A node with no parent is the root TreeModel represents the entire tree TreeNode represents a node TreePath represents a path to a node TreeModel does not directly store or manage tree data (different from the TableModel with JTables) MutableTreeNode represents a tree node that can be mutated by adding or removing child nodes or changing the content of the node TreeSelectionModel handles the tree node selection USC CSCI 201L 3/10

4 JTree Hierarchy USC CSCI 201L 4/10

5 JTree API USC CSCI 201L 5/10

6 JTree Example 1 import javax.swing.jframe; 2 import javax.swing.jpanel; 3 import javax.swing.jscrollpane; 4 import javax.swing.jtree; 5 6 public class Test extends JFrame { 7 public Test() { 8 super("tree Example"); 9 10 JPanel jp = new JPanel(); 11 String [] data = {"Cat", "Dog", "Fish", "Frog", "Salamander"}; JTree tree = new JTree(data); 14 tree.setrootvisible(true); 15 JScrollPane jsp = new JScrollPane(tree); 16 jp.add(jsp); 17 add(jp); setdefaultcloseoperation(jframe.exit_on_close); 20 setsize(500, 200); 21 setlocationrelativeto(null); 22 setvisible(true); 23 } public static void main(string args[]) { 26 Test t = new Test(); 27 } 28 } USC CSCI 201L 6/10

7 Tree Model Example 1 // import statements omitted 2 3 public class Test extends JFrame { 4 public Test() { 5 super("tree Example"); 6 7 JPanel jp = new JPanel(); 8 DefaultMutableTreeNode root, europe, northamerica, us; 9 europe = new DefaultMutableTreeNode("Europe"); 10 europe.add(new DefaultMutableTreeNode("UK")); 11 europe.add(new DefaultMutableTreeNode("Germany")); 12 europe.add(new DefaultMutableTreeNode("France")); 13 europe.add(new DefaultMutableTreeNode("Norway")); northamerica = new DefaultMutableTreeNode("North America"); 16 us = new DefaultMutableTreeNode("US"); 17 us.add(new DefaultMutableTreeNode("California")); 18 us.add(new DefaultMutableTreeNode("Texas")); 19 us.add(new DefaultMutableTreeNode("New York")); 20 us.add(new DefaultMutableTreeNode("Florida")); 21 us.add(new DefaultMutableTreeNode("Illinois")); 22 northamerica.add(us); 23 northamerica.add(new DefaultMutableTreeNode("Canada")); root = new DefaultMutableTreeNode("World"); 26 root.add(europe); 27 root.add(northamerica); JPanel panel = new JPanel(); 30 panel.setlayout(new GridLayout(1, 2)); 31 // next two lines create different instances of trees with the same nodes 32 panel.add(new JScrollPane(new JTree(root))); 33 panel.add(new JScrollPane(new JTree(new DefaultTreeModel(root)))); 34 JTextArea jtamessage = new JTextArea(); 35 jtamessage.setwrapstyleword(true); 36 jtamessage.setlinewrap(true); 37 add(new JSplitPane(JSplitPane.VERTICAL_SPLIT, panel, new JScrollPane(jtaMessage)), BorderLayout.CENTER); // Get tree information 40 jtamessage.append("depth of the node US is " + us.getdepth()); 41 jtamessage.append("\nlevel of the node US is " + us.getlevel()); 42 jtamessage.append("\nfirst child of the root is " + root.getfirstchild()); 43 jtamessage.append("\nfirst leaf of the root is " + root.getfirstleaf()); 44 jtamessage.append("\nnumber of the children of the root is " + root.getchildcount()); 45 jtamessage.append("\nnumber of leaves in the tree is " + root.getleafcount()); 46 String breadthfirstsearchresult = ""; // Breadth-first traversal 49 Enumeration bf = root.breadthfirstenumeration(); 50 while (bf.hasmoreelements()) { 51 breadthfirstsearchresult += bf.nextelement().tostring() + " "; 52 } 53 jtamessage.append("\nbreath-first traversal from the root is " + breadthfirstsearchresult); setdefaultcloseoperation(jframe.exit_on_close); 56 setsize(500, 200); 57 setlocationrelativeto(null); 58 setvisible(true); 59 } public static void main(string args[]) { 62 Test t = new Test(); 63 } 64 } USC CSCI 201L 7/10

8 More Tree Details JTree can fire a TreeSelectionEvent and a TreeExpansionEvent When a new node is selected, a TreeSelectionEvent is fired To handle the TreeSelectionEvent, a listener must implement the TreeSelectionListener interface When a node is expanded or collapsed, a TreeExpansionEvent is fired To handle the TreeExpansionEvent, a listener must implement the TreeExpansionListener interface (or extend TreeExpansionAdapter) USC CSCI 201L 8/10

9 Outline Trees Program USC CSCI 201L

10 Program Create the following GUI. 10/10