What is Swing, Is swing is thread-safe in Java?

Question

I am using Java's Swing here to make a UI application. I have a created a JFrame, with some buttons. When I click on this button, I want a new JFrame with some different content at this place. However, I do not want a new JFrame to load here.
One approach, I know is of setting the visbility of the second JFrame to be True in the actionPerformed(ActionEvent obj) method of the button in the first JFrame. But it again loads a new JFrame and I don't want that.

public class FirstUI extends JFrame {
    JButton but1;
    public FirstUI(){
        but1= new JButton("Click here");
        add(but1);

    XYZ obj= new XYZ():
    but1.addActionListener(obj);
    }

    public class XYZ implements ActionListener{
        public void actionPerformed(ActionEvent obj1){

             // WHAT TO DO HERE  
        } 
    }
}

I only want a single JFrame whose content changes as we click on different buttons. How can I achieve that ?

Answer 1

Swing is a set of program component s for Java programmers that provide the ability to create graphical user interface ( GUI ) components, such as buttons and scroll bars, that are independent of the windowing system for specific operating system . Swing components are used with the Java Foundation Classes ( JFC ).

Simple answer is - "that's the design choice the Swing team made". It is a well-known fact that writing thread safe API/library is more difficult and inefficient.

So to simplify the implementation of Swing library they chose it to be not thread safe. The argument being that most of the GUI related work happens in the callbacks from the GUI which happen on the single GUI thread anyways. Granted - for long running tasks the user will have to do more work if he/she wants to do multithreaded activity. Not making Swing thread safe allowed them to implement the Swing which covered a lot more ground (new controls, layouts, keyboard actions, layered pane etc) in a short amount of time.

It is not that bad though - Swing does provide a mechanism to deal with the issues of threading -

javax.swing.SwingUtilities.invokeLater(Runnable ...);
javax.swing.SwingUtilities.invokeAndWait(Runnable ...);
javax.swing.JProgressBar class
javax.swing.ProgressMonitor
javax.swing.ProgressMonitorInputStream
SwingWorker