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Java GridBadLayout positioning

I would be grateful for any help/suggestion regarding my problem. I attached the image of my simple program which shows that the positioning of the components seems a bit off. My question is - why the ComboBox From... as well as TextField Enter value here... start so far off of the left corner? I've given gridx=0 so it positions the component on the very edge of the window, but components start some pixels off from the edge. How can I fix it?
Also, what do I need to do/consider to remove dependency of the rows on each other? I mean how to position components anywhere I want in one row without effecting the position of other components in another row. Thank you!
Piece of Code:
JPanel container = new JPanel();
container.setLayout(new GridBagLayout());
getContentPane().add(container, BorderLayout.NORTH);
TitledBorder outputCenter;
GridBagConstraints c = new GridBagConstraints();
label = new JLabel("Choose measure system to convert");
label.setFont(new Font("Times New Roman", Font.PLAIN, 20));
c.gridx = 1;
c.gridy = 0;
c.gridwidth = 2;
c.insets = new Insets(10, 0, 20, 0);
container.add(label, c);
fromList = new JComboBox<String>(convertFrom);
c.gridx = 0;
c.gridy = 1;
c.gridwidth =1;
c.ipadx = 20;
c.anchor = GridBagConstraints.LINE_START;
container.add(fromList, c);
toList = new JComboBox<String>(convertTo);
c.gridx = 1;
c.gridy = 1;
c.gridwidth = 1;
c.ipadx = 20;
container.add(toList, c);
//Field where user enters the value to be converted
input = new JTextField("Enter value here...");
input.setPreferredSize(new Dimension(150,30));;
input.setEditable(true);
input.setBackground(Color.WHITE);
input.setBorder(BorderFactory.createLineBorder(Color.BLACK));
input.addMouseListener(new MouseAdapter(){
public void mouseClicked(MouseEvent e){
input.setText("");}});
c.gridx = 0;
c.gridy = 2;
c.gridwidth = 1;
c.ipady = 20;
container.add(input, c);
//The area where the output/result is shown
output = new JTextArea(10,30);
output.setEditable(false);
output.setFont(new Font("Serif", Font.BOLD, 12));
output.setBackground(Color.WHITE);
outputCenter = BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.BLACK), "Output");
outputCenter.setTitleJustification(TitledBorder.CENTER);
output.setBorder(outputCenter);
c.gridx = 1;
c.gridy = 2;
c.insets = new Insets(50,5,10,10);
c.gridwidth = 3;
container.add(output, c);
//Convert button
convert = new JButton("Convert");
c.gridx = 0;
c.gridy = 3;
c.ipadx = 50;
container.add(convert, c);
}
Output:

Remember, GridBagLayout is a "flexible grid" layout manager. It still relies on the concept of rows and columns, but each row and column has it's own size, based on the requirements of the components and the constraints applied to them.
This means, that you combo box is been aligned to the left position because of a combination of c.anchor = GridBagConstraints.LINE_START and the space requirements of the JTextField sharing the same column.
You "could" change c.anchor = GridBagConstraints.LINE_START to c.anchor = GridBagConstraints.LINE_END, while will (in your case) align the combo box to the right edge of the column, for example...
Another solution would be to use a combination of containers to reduce the overall complexity of the layout. For example, you could add both the combo boxes to their own container, managing the layout requirements for them in an isolated manner and then layout that container within the large scheme of things

Does GridBagLayout require placeholder panels for empty cells?

I made a simple GridBagLayout which adds buttons in the cells (0,0), (1,0), and (0,1).
JPanel panelMain = new JPanel(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
c.gridx = 0;
c.gridy = 0;
panelMain.add(new JButton("0,0"),c);
c.gridx = 1;
c.gridy = 0;
panelMain.add(new JButton("1,0"),c);
c.gridx = 0;
c.gridy = 1;
panelMain.add(new JButton("0,1"),c);
I was happy to see the resultant UI:
I want to add a JButton in a cell that is not connected to the existing cells. I want it to be separated by an empty space. When I try this, the new JButton is lumped in next to the others. Here is the addition:
JPanel panelMain = new JPanel(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
c.gridx = 0;
c.gridy = 0;
panelMain.add(new JButton("0,0"),c);
c.gridx = 1;
c.gridy = 0;
panelMain.add(new JButton("1,0"),c);
c.gridx = 0;
c.gridy = 1;
panelMain.add(new JButton("0,1"),c);
c.gridx = 3;
c.gridy = 0;
panelMain.add(new JButton("3,0"),c);
The output:
The JButton("3,0") is displaying at the cell (2,0). Do I need to use an empty JPanel as a place holder in the cell (2,0)? More importantly, why is this happening?

The layout does not know what should be the width to be left at 2,0 unless there is a component placed in the gridx = 2. By the time you complete the UI, if any component gets placed, it should look fine. For e.g.:
In other case you may add empty JPanel with background color matching to the background color of the container.

Do I need to use an empty JPanel as a place holder in the cell (2,0)?
You can use an "insets" grid bag constraint to give space between components. Read the Swing tutorial on How to Use GridBagLayout for more information on the inset constraint.
Or, if you want to have a place holder then you can use a Box.createHorizontalStrut(...) to easily specify the width.
More importantly, why is this happening?
Cells don't have a size unless there is a component in the cell. Each cell is independent of one another so what size would you expect cell (2,0) to be?

Weird layout using GridBagConstraints

I have several methods which create their own component, JButton or JLabel in a JPanel. Then I have a separate method which adds all these JPanels the the JFrame. I also use gridx and gridy on the JPanels to position them how I want. This is: lookreply on the left, then top right the title and below in a 2X2 table quit, restart, pickup and hello. However my current code when run displays a weird, random layout.
The lookreply is on the left, but then to the right is quit, a space, restart then hello all vertical. pickup and title aren't seen. I dont know why this is happening.
Please see my code below.:
public class GUI extends JPanel
{
/**
* Creation of variables used throughout the GUI Class.
*/
//JPanel panel = new JPanel(new GridBagLayout());
private static final long serialVersionUID = 1L;
public static void main(String[] args)
{
GUI g = new GUI();
g.create();
}
private void create()
{
JFrame screen = new JFrame("Dungeon of Doom");
screen.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
screen.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
//set size to full screen.
screen.setExtendedState(Frame.MAXIMIZED_BOTH);
//Add all JPanes to screen
screen.add(lookReply(), c);
c.gridy = 0;
c.gridx = 0;
screen.add(title(), c);
c.gridy = 0;
c.gridx = 1;
c.gridwidth = 2;
screen.add(quit(), c);
c.gridy = 1;
c.gridx = 1;
screen.add(restart(), c);
c.gridy = 1;
c.gridx = 2;
screen.add(pickup(), c);
c.gridy = 2;
c.gridx = 1;
screen.add(hello(), c);
c.gridy = 2;
c.gridx = 2;
screen.setVisible(true);
}
One of the methods (quit)
private JPanel quit()
{
JPanel quitPanel = new JPanel(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
JButton quit = new JButton("QUIT");
quitPanel.add(quit, c);
return quitPanel;
}
All the other methods are pretty much the same except the title is a a JLabel and the table iterates to create a 5x5 table of JLabel within its own JPanel. Any help is appreciated!

I have found what was doing this.
As seen in the code I was adding the component before setting the layout.
screen.add(lookReply(), c);
c.gridy = 0;
c.gridx = 0;
whereas it should be
c.gridy = 0;
c.gridx = 0;
screen.add(lookReply(), c);

gridheight moves component on top of each other

I have a JFrame which consists mainly of a left and right side. The left has 2 components 1 above the other, and the right has 9, again 1 on top of each other. As the left has 2, I want 1 component to equal the same vertical space as 6 on the right. I am using the gridBagConstraints layout and have each JPanel positioned in the main JFrame. Everything looks OK (apart from what I was just saying). To sort this problem I use c.gridHeight = 6 on the JPanel on the left. However this then puts the 6 JPanels which are on the right ontop of each other, ignoring their formatting. How can I rectify this problem? Snipets of my code which still cause the same problem are:
void create()
{
JFrame screen = new JFrame("Dungeon of Doom");
screen.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
screen.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
screen.setSize(new Dimension(screenWidth, screenHeight));
screen.setPreferredSize(new Dimension(screenWidth, screenHeight));
//Add all JPanes to screen
c.gridy = 0;
c.gridx = 0;
c.gridheight = 6;
screen.add(lookReply(), c);
c.gridy = 0;
c.gridx = 1;
screen.add(title(), c);
c.gridy = 1;
c.gridx = 1;
screen.add(space(), c);
c.gridy = 2;
c.gridx = 1;
screen.add(commands(), c);
//...So on, same for others
}
A sample method - the JPanel - all methods have the same content just different titles and less/more buttons/labels
private JPanel title()
{
JPanel titlePanel = new JPanel(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
titlePanel.setBackground(Color.red);
titlePanel.setOpaque(true);
JLabel title = new JLabel("DOD");
titlePanel.add(title, c);
return titlePanel;
}
I put a background on the JPanels just to help see where they are in the window
All help appreciated! Thanks :)

Choosing a layout manager

I'm trying to set up a couple of labels and textfields in a table-like style.
Currently I'm using the GridLayout, which kind of works as I want it to. However, the TextFields and Button is expanding to the full size of the cell.
How can I make the TextFields and Button "normal" sized, and what Layout Manager would accomplish this the easiest way?
Here's the current code and a screenshot:
JPanel forms = new JPanel();
forms.setLayout(new GridLayout(3, 2));
JLabel lbl_navn = new JLabel("Virksomhedsnavn:");
JTextField txt_navn = new JTextField();
JLabel lbl_adresse = new JLabel("Adresse:");
JTextField txt_adresse = new JTextField();
forms.add(lbl_navn);
forms.add(txt_navn);
forms.add(lbl_adresse);
forms.add(txt_adresse);
forms.add(Box.createRigidArea(new Dimension(10, 10)));
forms.add(new JButton("Opret virksomhed"));

I suggest you use gridBagLayout:
http://docs.oracle.com/javase/tutorial/uiswing/layout/gridbag.html
As an example:
JPanel forms = new JPanel();
forms.setLayout(new GridBagLayout());
JLabel lbl_navn = new JLabel("Virksomhedsnavn:");
JTextField txt_navn = new JTextField();
JLabel lbl_adresse = new JLabel("Adresse:");
JTextField txt_adresse = new JTextField();
//Setting grid bag constraints
GridBagConstraints c = new GridBagConstraints();
// Grid position coordinates
c.gridx = 0; c.gridy = 0;
//Align panel in top-left corner
c.anchor=GridBagConstraints.LINE_START;
forms.add(lbl_navn, c);
c.gridx = 1; c.ipadx = 195;
forms.add(txt_navn, c);
c.gridy = 1; c.gridx = 0; c.ipadx = 0;
forms.add(lbl_adresse, c);
c.gridx = 1; c.ipadx = 195;
forms.add(txt_adresse,c);
c.gridy = 2; c.gridx = 0; c.ipadx = 0;
forms.add(Box.createRigidArea(new Dimension(10, 10)),c);
c.anchor=GridBagConstraints.CENTER;
c.gridy = 2; c.gridx = 1;
forms.add(new JButton("Opret virksomhed"),c);
Hope this helps.

I think you can refer to this question where useful answers have been given:
JTextField Fixed Height

I read good things about Mig layout a while ago, I never used, but seems very powerful.
Check this Mig layout, may be a good solution for your problems.
UPDATE:
Mig layout is not a "standard" layout from sun/oracle.
GridBagLayout as mentioned, can accomplished your objectives(from experience). I personally when I want fixed sizes components I use to work with "null layouts".