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Why is Java not executing Commands in chronological order?

I had this question while setting a JLabel visible when a button is clicked it is like a loading icon. The p.make() method is executed but the Label is still invisible after the Method returns the Label is visible.
Can someone explain what is happening?
ActionPerformed:
String[] args = {jTextFieldDrgzusatzVariable.getText(),jTextFieldAusgabe.getText(),"C:\\CPOracle",jTextFieldKatalog.getText()};
this.jLblLoading.setVisible(true);
if(jLblLoading.isVisible()){
try{
new P21Make(args[0],args[1],args[2],args[3]).make();
}catch(Exception e){
e.printStackTrace();
}
}

The reason is very simple: Swing is single threaded (see the Swing concurrency tutorial for more information).
What happens is that the actionPerformed method is called on the Swing thread (the E(vent)D(ispatch)T(hread)). When the
this.jLblLoading.setVisible(true);
statement is reached, it will immediately mark the jLblLoading as visible. However, this has no effect yet on the UI. The UI needs to be repainted before the change in visibility has any effect. This repaint is scheduled on the EDT (which is not the same as immediately executed).
This explains why your
if(jLblLoading.isVisible()){
check succeeds, and you still do not see the difference in the UI. The component is marked as visible, but the repaint is still pending. The repaint will remain pending until the EDT becomes available again. Since the thing that is currently occupying the EDT is your actionPerformed call, the rest of the code in that actionPerformed method will be executed before the repaint (meaning before you see a change in the UI).
Your solution using a different thread can indeed fix this. You can however only use that if the new P21Make(...).make() does not affect the UI. If that statement interacts with Swing components in any way, it should be executed on the EDT. In that case, an alternative is to wrap the statement in a SwingUtilities#invokeLater call.

You should probably look at using SwingUtilities.invokeLater to allow actions which modify the gui to complete.
http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html

setVisible and requestFocus on textField

I have action thread and since it is Swing software, EDT.
I want my program to draw dialog window, and when it appears and it's filled with data, I want to get focus on selected text field.
Code flow: When I execute, it will run main thread, which calls method to draw dialog in invokeLater on EDT. Then program proceeds and in main thread it calls next methods that are being run in ED thread, again using invokeLater.
Problem: When I run it normally, it will not get focus on my text field.
Observation: But when I add some sleep (300 milis) to main thread, introducing time gap between one invokeLater call and next call in EDT, it works just like I want.
It seems to me like two actions added to AWT queue must be separated by some time, otherwise the second one doesn't work. I mean here setVisible(true) on dialog, and then requestFocus() on textField. Maybe requestFocus() only work when it sees dialog window drawn?
Question:How can I make things work, some synchronization method, maybe checking on dialog before calling requestFocus() (may be hard, because its in other class).
Solution:I forgot about most important thing - after calling setVisible() next thing I do is call to setEnabled(false) so user cannot do anything before data filling is completed. The problem was there, in setEnabled() I also was adding tasks to AWT queue (by invokeLater()). This task caused corruption of next steps. What I do now to fix it is calling this setEnabled(false) from my main thread inside invokeAndWait(). If I understand it correctly, now the dialog popup section is called first, and then main thread waits until EDT proceed his work and then setEnabled(false) is called. So technically user is not enabled to do anything after the window is drawn, which makes sense for me.
Anyway thanks for your responses.

It's better to call the focus setting from the dialog. Add a WindowListener to the dialog and use either
public void windowOpened(WindowEvent e)
public void windowActivated(WindowEvent e);
to set focus on the JTextField instance

The requestFocusInWindow() method can only be invoked on a visible component. That means the frame/dialog must already be visible when you invoke the method.
If you are trying to do this on a modal dialog you may have problems. Check out Dialog Focus for a simple listener you can use to set focus on a component.

label.setVisible(true) doesn't do anything until after process completes

I have a dialog containing several buttons. When a particular button is clicked, it's ActionListener iniates a process that takes several seconds to complete. During this time I want to provide some feedback to the user. To take a simple approach, I have a label in the dialog "Computing..." which is initially not visible. A code segment looks like this
button_OpenHoursReport.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
lbl_Computing.setVisible(true);
new runAndRenderReport();
RunAndRenderReport.main(null);
lbl_Computing.setVisible(false);
}
});
The problem is, the lbl_Computing text does not become visible until the RunAndRenderReport is completed. Obviously, that's not much help to the user. Don't know where to go from here. Does this have to do with threads? If so, I could use some guidance on how to get started.

actionPerformed() is executed on the GUI-thread (EDT), so avoid executing intensive operations on it. Instead use SwingWorker.
See How SwingWorker works.

A trick which is much easier than using SwingWorker is to call paintImmediately on your label after calling setVisible(true). You should see the effects - immediately.
lbl_Computing.paintImmediately(0, 0, lbl_Computing.getWidth(), lbl_Computing.getHeight());
But SwingWorker is the way to go if you want your GUI to be responsive in other ways as well while the reporting is running.

Using Threads to perform operations on same jframe

i need to develop java code to have JFrame with a text filed and button.Using Threads,i need to update time for every one minute in the title bar of JFrame.Using Another Thread i need to display textbox value in the console when a button is clicked.I have code for performing both operations (updating time for every min and getting text box value)but i dont know how to add two threads in same class.if anyone knows pls help me out

What you are asking is a dangerous thing to do in Swing. Swing components are not thread-safe and should only be updated from the Event Dispatching Thread (also known as the EDT or Swing Thread). To do this, Swing has utility methods such as SwingUtilities.invokeLater(Runnable) which will execute the code in the Runnable (at some point in the future) on the EDT. The idea is that you place your code to do Swing-things (like update the Title of the JFrame with the time) inside of a separate Runnable and pass it to invokeLater().
To do this, you can create an anonymous Runnable class:
Runnable updateJFrame = new Runnable () {
public void run () {
myJFrame.setTitle("My New Title");
}
};
SwingUtilities.invokeLater(updateJFrame);
Using invokeLater() also ensures that the components get refreshed/repainted properly after they have been updated. (The behavior you are seeing when using statics may actually be a refresh/repaint issue.) The moral of this story is that if you manipulate Swing components on a non-EDT thread, all bets are off.

Java - Swing JLabel updates too quickly?

In a method of a class, I update the same label twice. The first time, it shows the user message to wait, but the second time shows the user the completed message. Something like the following:
MyClass{
myMethod(){
jLabel.setText("Please wait...");
//does calculation
jLabel.setText("Completed successfully!");
}
}
When I run the app, all I see is the "Completed successfully" message. Is the JLabel updating too quickly? How do I control it? I tried using the following but no luck :(
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
jLabel.setText("Please wait...");
}
});

If the calculation is done in the event dispatch thread, then it blocks the thread and prevents it from doing all its repaintings. You must do the computation in another thread, and have this thread change the label text when it ends (in the event dispatch thread, using SwingUtilities.invokeLater, or by using the SwingWorker mechanism). If the computation is really fast, it's not worth it, though, because the second text will appear so quickly after the first one that you won't even notice the first one.
Have a look at SwingWorker, which is designed for such use-cases. Its javadoc contains a useful example.

if you want to delay some Action/Event then use javax.swing.Timer, or wrap your code to the Runnable#Thread,
notice: never use Thread.sleep(int) durring EDT, your GUI freeze until Thread.sleep(int) ended
example for javax.swing.Timer & Runnable#Thread & Freeze GUI by implements Thread.sleep(int) durring EDT here

Possibly because your calculations are happening too fast. Did you try putting a delay after your calc.
Also as Nizet points out above if this is happening in EDT the component will not repaint until end of the thread which means it will take the last set value.