applet vs. program?

[John Ringo]

I've searched on this here and I can't find the answer. My question is pretty basic. So far I've gotten a few applets to compile and run, but when I try make a program out of them I can't make it happen. I want to be able to just type java "classname" and run it without using applet viewer or a browser.
I'm adding the "public static void main (String[] args)" line I can't get them to compile, let alone run as a program. I get the following error: 'class' or 'interface' expected. It doesn't seem to matter where I add this line.
I would appreciate any help anyone can provide. Thanks in advance.

[Dave Vick]

John
Can you post the code where the error is occuring? It sounds like some sort of a syntax error, you might a brace out of place or a declaration that looks like a class or interface to the compiler but it isn't.

[John Ringo]

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
 
public class CalcEvent extends Applet implements ActionListener {
    
    private Button key0,key1,key2,key3,key4,key5,key6,key7,key8,key9;
    private Button keyequal,keyplus,keyminus,keyperiod,keymult,keydiv;
    private Panel buttonArea;
    
    private TextField answer;
    private String current;
    private boolean periodSet = false;
    private boolean clearNow = false;
    private boolean clearAfter = false;
    private double firstNumber = 0;
    private String lastMethod;
    
    public void init() {
        answer = new TextField(15);
        answer.setEditable(false);
        
        key0 = new Button("0");
        key1 = new Button("1");
        key2 = new Button("2");
        key3 = new Button("3");
        key4 = new Button("4");
        key5 = new Button("5");
        key6 = new Button("6");
        key7 = new Button("7");
        key8 = new Button("8");
        key9 = new Button("9");
        keyequal = new Button("=");
        keyplus = new Button("+");
        keyminus = new Button("-");
        keymult = new Button("*");
        keydiv = new Button("/");
        keyperiod = new Button(".");
        
        key0.addActionListener(this);
        key1.addActionListener(this);
        key2.addActionListener(this);
        key3.addActionListener(this);
        key4.addActionListener(this);
        key5.addActionListener(this);
        key6.addActionListener(this);
        key7.addActionListener(this);
        key8.addActionListener(this);
        key9.addActionListener(this);
        keyplus.addActionListener(this);
        keyminus.addActionListener(this);
        keymult.addActionListener(this);
        keydiv.addActionListener(this);
        keyequal.addActionListener(this);
        keyperiod.addActionListener(this);
        
        buttonArea = new Panel();
        buttonArea.setLayout(new GridLayout(4,3));
        
        buttonArea.add(key7);
        buttonArea.add(key8);
        buttonArea.add(key9);
        buttonArea.add(keyplus);
        buttonArea.add(key4);
        buttonArea.add(key5);
        buttonArea.add(key6);
        buttonArea.add(keyminus);
        buttonArea.add(key1);
        buttonArea.add(key2);
        buttonArea.add(key3);
        buttonArea.add(keymult);
        buttonArea.add(key0);
        buttonArea.add(keyperiod);
        buttonArea.add(keyequal);
        buttonArea.add(keydiv);
    }
    
    public void start() {
        setLayout(new BorderLayout());
        add("North",answer);
        add("Center",buttonArea);
    }
    
    public void actionPerformed (ActionEvent e) {
        String bLabel = (String)e.getActionCommand();
        
        if (clearNow) {
            if (lastMethod == "equal" && (bLabel.equals("+") ||
                bLabel.equals("-") || bLabel.equals("*") ||
                bLabel.equals("/"))) {
                
                clearNow = false;
            } else {
                answer.setText("");
                clearNow = false;
            }
        }
        
        String current = answer.getText();
        
        if (bLabel.equals(".")) {
            if (!periodSet) {
                periodSet = true;
                answer.setText(current+".");
            }
        } else if (bLabel.equals("+")) {
            
            if (lastMethod == "plus") {
                firstNumber += Double.valueOf(current).doubleValue();
            } else if (lastMethod == "minus") { 
                firstNumber -= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "mult") {
                firstNumber *= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "div") {
                firstNumber /= Double.valueOf(current).doubleValue();
            } else {
                firstNumber = Double.valueOf(current).doubleValue();
            }
            
            lastMethod = "plus";
            periodSet = false;
            clearNow = true;
            
        } else if (bLabel.equals("-")) {
            
            if (lastMethod == "plus") {
                firstNumber += Double.valueOf(current).doubleValue();
            } else if (lastMethod == "minus") { 
                firstNumber -= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "mult") {
                firstNumber *= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "div") {
                firstNumber /= Double.valueOf(current).doubleValue();
            } else {
                firstNumber = Double.valueOf(current).doubleValue();
            }
            
            lastMethod = "minus";
            periodSet = false;
            clearNow = true;
            
        } else if (bLabel.equals("*")) {
            
            if (lastMethod == "plus") {
                firstNumber += Double.valueOf(current).doubleValue();
            } else if (lastMethod == "minus") { 
                firstNumber -= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "mult") {
                firstNumber *= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "div") {
                firstNumber /= Double.valueOf(current).doubleValue();
            } else {
                firstNumber = Double.valueOf(current).doubleValue();
            }
            
            lastMethod = "mult";
            periodSet = false;
            clearNow = true;
            
        } else if (bLabel.equals("/")) {
            
            if (lastMethod == "plus") {
                firstNumber += Double.valueOf(current).doubleValue();
            } else if (lastMethod == "minus") { 
                firstNumber -= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "mult") {
                firstNumber *= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "div") {
                firstNumber /= Double.valueOf(current).doubleValue();
            } else {
                firstNumber = Double.valueOf(current).doubleValue();
            }
            
            lastMethod = "div";
            periodSet = false;
            clearNow = true;
            
        } else if (bLabel.equals("=")) {
            
            if (lastMethod == "plus") {
                firstNumber += Double.valueOf(current).doubleValue();
            } else if (lastMethod == "minus") { 
                firstNumber -= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "mult") {
                firstNumber *= Double.valueOf(current).doubleValue();
            } else if (lastMethod == "div") {
                firstNumber /= Double.valueOf(current).doubleValue();
            }
            
            answer.setText(new Float(firstNumber).toString());
            firstNumber = 0;
            clearNow = true;
            lastMethod = "equal";
            
        } else {
            answer.setText(current+bLabel);
        }
    }
    
}
 
public static void main (String[] args) {}

I've tried to add the main method right before and after the CalcEvent class declaration, but no luck. Thanks!
[ May 07, 2002: Message edited by: Dirk Schreckmann ]

[Ria Mathur]

The main() method needs to be inside the the class.
Hope it helps,
- Ria

[Roy Ben Ami]

its not that easy....
you need to extend from Frame instead of Applet.
also add these lines:
setVisible(true);
setBounds(0,0,350,350);
in the main method you need to create an object of your classand activate the start method on it.
so:

public static void main(String args[])
{
   CalcEvent object=new CalcEvent();
   object.start();
}
  

also the main should be in the class as been pointed out.

[John Ringo]

Thanks for the replies Ria and Roy. When I do all that it compiles okay. It's actually making more sense to me now, and I thank you both for that. When I do exactly what Roy said about extendend from Frame, setBounds, setVisible, and making the main object it compiles and I get the follwing when I run it with "java CalcEvent.":
Exeption in Thread "main" Java.lang.NullPointerException
at java.awt.Container.addImpl(Container.java:439)
at java.awt.Container.add(Container.java:3100
at CalcEvent.start(CalcEvent.java:82)
at CalcEvent.main(CalcEvent.java:186)
I've tried to add a throws clause for the start and main, but no it didn't work... maybe I should use a try/catch... I have no idea what to do about two AWT exceptions anyway. Any more ideas would be apprecaited.

[Roy Ben Ami]

ok my mistake.
make sure u add the lines setVisible() and setBounds() i told you about to the end of the init() method.
also call the init() method before you call the start() method like this:

public static void main(String args[])
{  
 CalcEvent object=new CalcEvent();   
object.init();
object.start();  
}

[John Ringo]

Thanks for the help Roy... works fine. The best thing is I actually understand it now, I think. I had to put the setVisible in both the init and start methods. Thanks again. It's fun to see this stuff actually work.