How to use enumeration method deal with sets?

Question

hi,
friends, i have some troubles to compile my program on deal with Set.
here is the problem:
A:\>javac Set.java
Set.java:145: Reference to variable set2 in class Set as if it were a method.
if (set1.contains(elem) != set2(elem))
^
Set.java:189: Wrong number of arguments in method.
loadResult(set1.complement(set2));
^
Set.java:191: Wrong number of arguments in method.
loadResult(set1.symmetricComplement(set2));
^
3 errors
i marked the related part with ???. please help.
thank you very much.
my program as following:
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.util.*;
import java.io.*;
public class Set extends Applet implements ActionListener,                               ItemListener{
Button add, union, intersect, clear, complement,symmetricComplement;
     List set1List, set2List, activeList, resultList;
     Checkbox set1Selector, set2Selector;
     CheckboxGroup selectorGroup;
     TextField value;
     Set set1, set2, activeSet;
     Vector vector;
     private Button makeButton(String label, Color color) {
          Button b = new Button(label);
          b.setBackground(color);
          b.setFont(new Font("Courier", Font.BOLD, 10));
          return b;
     private Panel makePanel(LayoutManager lm, Color c) {
          Panel p = new Panel();
          p.setLayout(lm);
          p.setBackground(c);
          return p;
     public void init () {
     set1 = new Set();
     set2 = new Set();     //componets
     setLayout(new BorderLayout());
                    //checkboxes
     set1Selector = new Checkbox("Set 1");
     set1Selector.addItemListener(this);
     set2Selector = new Checkbox("Set 2");
     set2Selector.addItemListener(this);
     selectorGroup = new CheckboxGroup();
     set1Selector.setCheckboxGroup(selectorGroup);
     set2Selector.setCheckboxGroup(selectorGroup);
     Panel p = new Panel();
     p.add(set1Selector);
     p.add(set2Selector);
     add("North", p);
                    //Lists
     set1List = new List();
     set1List.setBackground(Color.white);
     set2List = new List();
     set2List.setBackground(Color.white);
     resultList = new List();
     resultList.setBackground(Color.white);
     p = new Panel();
     p.add(new Label("Set1"));
     p.add(set1List);
     p.add(new Label("Set2"));
     p.add(set2List);
     p.add(new Label("Result"));
     p.add(resultList);
     add("Center", p);
                    //Buttons
     add = new Button("Add:");
     add.addActionListener(this);
     value = new TextField(5);
     clear = new Button("Clear");
     clear.addActionListener(this);
     union = new Button("Union");
     union.addActionListener(this);
     intersect = new Button("Intersect");
     intersect.addActionListener(this);
     complement = new Button("Complement");
     complement.addActionListener(this);
     symmetricComplement = new Button("SymmetricComplement");
     symmetricComplement.addActionListener(this);
     p = new Panel();
     p.add(add);
     p.add(value);
     p.add(clear);
     p.add(union);
     p.add(intersect);
     p.add(complement);
     p.add(symmetricComplement);
     add("South", p);
               //set active checkbox
     selectorGroup.setSelectedCheckbox(set1Selector);
     setActive();
     public Set() {
          vector = new Vector();
     public boolean isEmpty() {
     return vector.isEmpty();
     //public size() {
     //return vector.size();
     public boolean contains(Object o) {
     Enumeration enum = vector.elements();
     while (enum.hasMoreElements()) {
     Object elem = enum.nextElement();
     if (elem.equals(o))
     return true;
     return false;
     public void addElement(Object o) {
          if (!contains(o))
               vector.addElement(o);
     public Object copy() {
          Set destSet = new Set();
          Enumeration enum = vector.elements();
          while (enum.hasMoreElements())
               destSet.addElement(enum.nextElement());
          return destSet;
     public Set union(Set s) {
          Set unionSet = (Set)s.copy();
          Enumeration enum = vector.elements();
          while (enum.hasMoreElements())
               unionSet.addElement(enum.nextElement());
               return unionSet;
     public Set intersection(Set s) {
          Set interSet = new Set();
          Enumeration enum = this.vector.elements();
     while (enum.hasMoreElements()) {
               Object elem = enum.nextElement();
               if (s.contains(elem))
               interSet.addElement(elem);
          return interSet;
     public Set complement (Set set1, Set set2) {     //???
          Set complementSet = new Set();
          Enumeration enum = this.vector.elements();
     while (enum.hasMoreElements()) {
               Object elem = enum.nextElement();
          if (set1.contains(elem) != set2(elem))
               complementSet.addElement(elem);
          return complementSet;
     public Set symmetricComplement (Set set1, Set set2) { //???
          Set symmetricComplementSet = new Set();
          Enumeration enum = this.vector.elements();
     while (enum.hasMoreElements()) {
          Object elem = enum.nextElement();
          if (elem != set1.set2)
          symmetricComplementSet.addElement(elem);
          return symmetricComplementSet;
     void removeAllElements() {
     vector.removeAllElements();          //differ
     Enumeration elements() {
     return vector.elements();
     public void print(PrintStream ps) {
          String PrintStream;
          Enumeration enum = vector.elements();
          while (enum.hasMoreElements()) {
               ps.print(enum.nextElement().toString());
               ps.print(" ");
          //handles action events generated by the buttons
     public void actionPerformed(ActionEvent ae){
          if (ae.getSource() == add) {
          addElement();
          repaint();
          else if (ae.getSource() == union)          
          loadResult(set1.union(set2));
          else if (ae.getSource() == intersect)
          loadResult(set1.intersection(set2));
          else if (ae.getSource() == complement)
          loadResult(set1.complement(set2));     //???
          else if (ae.getSource() == symmetricComplement)
          loadResult(set1.symmetricComplement(set2)); //???
          else if (ae.getSource() == clear) {
          activeSet.removeAllElements();
          activeList.removeAll();
          //handles item events generated by the Checkboxes
     public void itemStateChanged(ItemEvent ie) {
          setActive();
     private void addElement() {
          int i = Integer.parseInt (value.getText());
          activeSet.addElement (new Integer(i));
          activeList.addItem (Integer.toString(i));
     private void setActive() {
          List newActiveList;
          if (selectorGroup.getSelectedCheckbox() ==                               set1Selector){
               activeList = set1List;
               activeSet = set1;
          else {
               activeList = set2List;
               activeSet = set2;
     private void loadResult(Set resultSet){
          resultList.removeAll();
          Enumeration enum = resultSet.elements();
          while (enum.hasMoreElements())
          resultList.addItem (enum.nextElement().toString());
          repaint();

Answer 1

public Set complement (Set set1, Set set2) {
   Set complementSet = new Set();
   Enumeration enum = this.vector.elements();
   while (enum.hasMoreElements()) {
      Object elem = enum.nextElement();
      if (set1.contains(elem) != set2(elem))
         complementSet.addElement(elem);
   return complementSet;
}I'm not sure what you think you are doing with the set2(elem) call. You are treating a variable as if it were a method.
All you have to do is change set2(elem) to set2.contains(elem) and things would be fine. This is especially weird since you knew that for set1.