How to invoke a private class after clicking the button that work?

[Ket Nonting]

Hi guys,

I have an applet with the following structure:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Test extends JApplet implements ActionListener {

	private JLabel msg;
	private final String ButtonText = "Submit";
	private CoolStuffs DoCoolStuffs;

	public void init() {	
		// get the window/form surface--called a pane--that holds the buttons and other graphical content
		Container contentHolder = getContentPane();
		// indicate where the pane will go
		contentHolder.setLayout(new BorderLayout(30,30));
		// add the msg label
		msg = new JLabel("");
		contentHolder.add(msg, BorderLayout.CENTER);
		// make a panel for the button
		JPanel buttonPanel = new JPanel();
		// make a button
		JButton myButton = new JButton(ButtonText);
		// tell the button to use this class to respond when the button is pressed
		myButton.addActionListener(this);
		// add button to its panel
		buttonPanel.add(myButton);
		// add the button panel to the content pane
		contentHolder.add(buttonPanel, BorderLayout.SOUTH);
	}

	public void actionPerformed(ActionEvent evt) {	
		// get the text of the button that was pushed
		String command = evt.getActionCommand();
		// if myButton was pressed, output a message
		if(ButtonText.equals(command))
		msg.setText("Button Pressed");
		// invoke the CoolStuffs class
		DoCoolStuffs = new CoolStuffs();
	}

	private class CoolStuffs {
	}

}

The question is how do I invoke the CoolStuff class that real works. It just compiled and did not work. I can't find any tutorial on the web about this.

And another question, can I invoke a java code snippet to run inside the CoolStuffs class.

Thanks in advance.

[john price]

What exactly didn't work? Did you receive an error? If you did, please post it. What results were you expecting?

John Price

[Ket Nonting]

Sorry for it's taking so long to reply. It's kind of bit embarrassment. I'm new to java and didn't know if people have done this and I'm a laggard.
I'm trying to capture a screenshot with java applet but it didn't seem to work. I can't invoke the subclass set of java application to automate.
Bellow is my experimenting so far, would be greatly appreciated if you can point out where it went wrong:

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;

public class TestCapture extends JApplet implements ActionListener {

	private JLabel msg;
	private final String ButtonText = "Capture";
	private ScreenCapture capture;

	public void init() {	
		// get the window/form surface--called a pane--that holds the buttons and other graphical content
		Container contentHolder = getContentPane();
		// indicate where the pane will go
		contentHolder.setLayout(new BorderLayout(30,30));
		// add the msg label
		msg = new JLabel("");
		contentHolder.add(msg, BorderLayout.CENTER);
		// make a panel for the button
		JPanel buttonPanel = new JPanel();
		// make a button
		JButton myButton = new JButton(ButtonText);
		// tell the button to use this class to respond when the button is pressed
		myButton.addActionListener(this);
		// add button to its panel
		buttonPanel.add(myButton);
		// add the button panel to the content pane
		contentHolder.add(buttonPanel, BorderLayout.SOUTH);
	}

	public void actionPerformed(ActionEvent evt) {	
		// get the text of the button that was pushed
		String command = evt.getActionCommand();
		// if myButton was pressed, output a message
		if(ButtonText.equals(command))
		msg.setText("You have captured a screenshot");
		// invoke the ScreenCapture private class, utilizing a java desktop application
		capture = new ScreenCapture();
	}
	
	private class ScreenCapture {
		public void main(String args[]) throws AWTException, IOException {
			// capture screenshot of a specific area
			BufferedImage screencapture = new Robot().createScreenCapture(new Rectangle( 15, 15, 150, 150));
			// save file in a JPEG format
			File file = new File("screencapture.jpg");
			ImageIO.write(screencapture, "jpg", file);
		}
	}
}

[Paul Clapham]

// invoke the ScreenCapture private class, utilizing a java desktop application  
capture = new ScreenCapture();  

First of all, your comment is incorrect in that fragment from your post. You don't "invoke" a class in Java (except in that uncommon situation where you're running a class from the command line). What your code does is to create an instance of that class, nothing else. You apparently thought that "invoking" a class would call a method which happened to called "main". That's not the case either. If you want that method to be called, you're going to have to call it.

Although I wouldn't call it "main", that doesn't describe its function at all. I would call it "capture" or something like that. And I would get rid of the String-array parameter, since you don't use that anywhere in the method.

[Ket Nonting]

Thank Paul,

Your comment is complicated to me. I don't understand it right now, because I'm new to this java thing. But I would try to understand it. Maybe I should start with the "call" method you mentioned. The "invoke" word was just borrowed from Oracle's tutorial website. I don't really understand what does it mean right now.

[Paul Clapham]

New to Java? And you're writing an applet? I don't recommend that, you're going to get into all kinds of non-Java complexities if you do that. Start off by writing a plain old Java application first.

[Ket Nonting]

Thanks for suggestions. I've learned basic java programing. But the application didn't serve my purpose. I jump to an applet thing. That is very helpful suggestion. I will do this.