Composite pattern in Java
/*
The Design Patterns Java Companion
Copyright (C) 1998, by James W. Cooper
IBM Thomas J. Watson Research Center
*/
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Enumeration;
import java.util.Vector;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.border.BevelBorder;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
public class EmpTree extends JFrame implements TreeSelectionListener {
Employee boss, marketVP, prodVP;
Employee salesMgr, advMgr;
Employee prodMgr, shipMgr;
JScrollPane sp;
JPanel treePanel;
JTree tree;
DefaultMutableTreeNode troot;
JLabel cost;
public EmpTree() {
super("Employee tree");
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
makeEmployees();
setGUI();
}
//--------------------------------------
private void setGUI() {
treePanel = new JPanel();
getContentPane().add(treePanel);
treePanel.setLayout(new BorderLayout());
sp = new JScrollPane();
treePanel.add("Center", sp);
treePanel.add("South", cost = new JLabel(" "));
treePanel.setBorder(new BevelBorder(BevelBorder.RAISED));
troot = new DefaultMutableTreeNode(boss.getName());
tree = new JTree(troot);
tree.setBackground(Color.lightGray);
loadTree(boss);
/* Put the Tree in a scroller. */
sp.getViewport().add(tree);
setSize(new Dimension(200, 300));
setVisible(true);
}
//------------------------------------
public void loadTree(Employee topDog) {
DefaultMutableTreeNode troot;
troot = new DefaultMutableTreeNode(topDog.getName());
treePanel.remove(tree);
tree = new JTree(troot);
tree.addTreeSelectionListener(this);
sp.getViewport().add(tree);
addNodes(troot, topDog);
tree.expandRow(0);
repaint();
}
//--------------------------------------
private void addNodes(DefaultMutableTreeNode pnode, Employee emp) {
DefaultMutableTreeNode node;
Enumeration e = emp.elements();
while (e.hasMoreElements()) {
Employee newEmp = (Employee) e.nextElement();
node = new DefaultMutableTreeNode(newEmp.getName());
pnode.add(node);
addNodes(node, newEmp);
}
}
//--------------------------------------
private void makeEmployees() {
boss = new Employee("CEO", 200000);
boss.add(marketVP = new Employee("Marketing VP", 100000));
boss.add(prodVP = new Employee("Production VP", 100000));
marketVP.add(salesMgr = new Employee("Sales Mgr", 50000));
marketVP.add(advMgr = new Employee("Advt Mgr", 50000));
for (int i = 0; i < 5; i++)
salesMgr.add(new Employee("Sales " + new Integer(i).toString(),
30000.0F + (float) (Math.random() - 0.5) * 10000));
advMgr.add(new Employee("Secy", 20000));
prodVP.add(prodMgr = new Employee("Prod Mgr", 40000));
prodVP.add(shipMgr = new Employee("Ship Mgr", 35000));
for (int i = 0; i < 4; i++)
prodMgr.add(new Employee("Manuf " + new Integer(i).toString(),
25000.0F + (float) (Math.random() - 0.5) * 5000));
for (int i = 0; i < 3; i++)
shipMgr.add(new Employee("ShipClrk " + new Integer(i).toString(),
20000.0F + (float) (Math.random() - 0.5) * 5000));
}
//--------------------------------------
public void valueChanged(TreeSelectionEvent evt) {
TreePath path = evt.getPath();
String selectedTerm = path.getLastPathComponent().toString();
Employee emp = boss.getChild(selectedTerm);
if (emp != null)
cost.setText(new Float(emp.getSalaries()).toString());
}
//--------------------------------------
static public void main(String argv[]) {
new EmpTree();
}
}
class Employee {
String name;
float salary;
Vector subordinates;
boolean isLeaf;
Employee parent = null;
//--------------------------------------
public Employee(String _name, float _salary) {
name = _name;
salary = _salary;
subordinates = new Vector();
isLeaf = false;
}
//--------------------------------------
public Employee(Employee _parent, String _name, float _salary) {
name = _name;
salary = _salary;
parent = _parent;
subordinates = new Vector();
isLeaf = false;
}
//--------------------------------------
public void setLeaf(boolean b) {
isLeaf = b; //if true, do not allow children
}
//--------------------------------------
public float getSalary() {
return salary;
}
//--------------------------------------
public String getName() {
return name;
}
//--------------------------------------
public boolean add(Employee e) {
if (!isLeaf)
subordinates.addElement(e);
return isLeaf; //false if unsuccessful
}
//--------------------------------------
public void remove(Employee e) {
if (!isLeaf)
subordinates.removeElement(e);
}
//--------------------------------------
public Enumeration elements() {
return subordinates.elements();
}
//--------------------------------------
public Employee getChild(String s) {
Employee newEmp = null;
if (getName().equals(s))
return this;
else {
boolean found = false;
Enumeration e = elements();
while (e.hasMoreElements() && (!found)) {
newEmp = (Employee) e.nextElement();
found = newEmp.getName().equals(s);
if (!found) {
newEmp = newEmp.getChild(s);
found = (newEmp != null);
}
}
if (found)
return newEmp;
else
return null;
}
}
//--------------------------------------
public float getSalaries() {
float sum = salary;
for (int i = 0; i < subordinates.size(); i++) {
sum += ((Employee) subordinates.elementAt(i)).getSalaries();
}
return sum;
}
}
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