A DESCRIPTION OF THE REQUEST :
Assume a JPanel with 4 subcomponents in one line. The first subcomponent has filling NONE and the others BOTH. The JPanel has a fixed size.

The GridBagLayout actually computes the difference between actual width and the sum of the preferred widths of the subcomponents. Then the layout divides this difference through the number of components with horizontal filling. The result is added to each of the matching components.

But if the difference isn't an exact multiple of the number of matching components, the is a rest. This remaining space is inserted before the first subcomponent and after the last subcomponent. There is no way to decide, on which place the remaining space is to be inserted. If one wants to have containers with left alignment it would be nice, if the whole rest is inserted after the last component.

JUSTIFICATION :
Especially if one wants to desing forms with borders, one wants the field descriptions left aligned. If the contents of the lines is very different, one can't always avoid this problem, so you get steps in the borderlines at the transistions of close-by components. Also it is not always possible, to organize all the components through one single GridBagLayout, especially if the form is very large. So you have to use multiple Panels with GridBagLayouts. It would be helpful to configure the Layouts to avoid this problem.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I would like to have the possibility to configure for each GridBagLayout the way the layout distributes remaining spaces. In this case I would like to tell the GridBagLayout to insert remaining spaces completely after the last subcomponent.

Alternatively it would be nice if the default behaviour is to insert remaining spaces at the end of the line.
ACTUAL -
Assume to have 2 lines of the form, each represented by a JPanel with GridBagLayout. For the first line the remaining space is 2, for the second line it is 1. So the GridBagLayout for the first line inserts one pixel before the first subcomponent and one pixel after the last subcomponent. The GridBagLayout for the second line inserts only one pixel after the last subcomponent.
If the first subcomponent for each line has a border, the bordered subcomponent in the first line seams to be indented.

---------- BEGIN SOURCE ----------
import java.awt.*;
import javax.swing.*;

public class GridBagLayoutTest extends JFrame {

private JLabel firstLabel;
private JCheckBox firstButton1;
private JCheckBox firstButton2;
private JCheckBox firstButton3;
private JLabel secondLabel;
private JCheckBox secondButton1;
private JCheckBox secondButton2;
private JCheckBox secondButton3;

public GridBagLayoutTest() {
super();
this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

JPanel content = new JPanel(new GridBagLayout());
setContentPane(content);

JPanel firstLine = new JPanel(new GridBagLayout());

firstLabel = new JLabel("Zeile 1");
firstLabel.setBorder(BorderFactory.createLineBorder(Color.black));
GridBagConstraints c = new GridBagConstraints();
c.gridx = 0; c.gridy = 0;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.VERTICAL; c.anchor = GridBagConstraints.WEST;
c.weightx = 0.0; c.weighty = 1.0;
((GridBagLayout)firstLine.getLayout()).setConstraints(firstLabel, c);
firstLine.add(firstLabel);

firstButton1 = new JCheckBox("getötet");
c = new GridBagConstraints();
c.gridx = 1; c.gridy = 0;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.BOTH; c.anchor = GridBagConstraints.WEST;
c.weightx = 1.0; c.weighty = 1.0;
c.insets = new Insets(0, 3, 0, 0);
((GridBagLayout)firstLine.getLayout()).setConstraints(firstButton1, c);
firstLine.add(firstButton1);

firstButton2 = new JCheckBox("schwerverletzt");
c = new GridBagConstraints();
c.gridx = 2; c.gridy = 0;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.BOTH; c.anchor = GridBagConstraints.WEST;
c.weightx = 1.0; c.weighty = 1.0;
((GridBagLayout)firstLine.getLayout()).setConstraints(firstButton2, c);
firstLine.add(firstButton2);

firstButton3 = new JCheckBox("leichtverletzt");
c = new GridBagConstraints();
c.gridx = 3; c.gridy = 0;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.BOTH; c.anchor = GridBagConstraints.WEST;
c.weightx = 1.0; c.weighty = 1.0;
((GridBagLayout)firstLine.getLayout()).setConstraints(firstButton3, c);
firstLine.add(firstButton3);


firstLine.setPreferredSize(new Dimension(383, 30));
c = new GridBagConstraints();
c.gridx = 0; c.gridy = 0;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.HORIZONTAL; c.anchor = GridBagConstraints.WEST;
c.weightx = 1.0; c.weighty = 0.0;
c.insets = new Insets(10, 10, 0, 10);
((GridBagLayout)content.getLayout()).setConstraints(firstLine, c);
content.add(firstLine);


JPanel secondLine = new JPanel(new GridBagLayout());


secondLabel = new JLabel("Zeile 2");
secondLabel.setBorder(BorderFactory.createLineBorder(Color.black));
c = new GridBagConstraints();
c.gridx = 0; c.gridy = 0;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.VERTICAL; c.anchor = GridBagConstraints.WEST;
c.weightx = 0.0; c.weighty = 1.0;
((GridBagLayout)secondLine.getLayout()).setConstraints(secondLabel, c);
secondLine.add(secondLabel);

secondButton1 = new JCheckBox("getötet");
c = new GridBagConstraints();
c.gridx = 1; c.gridy = 0;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.BOTH; c.anchor = GridBagConstraints.WEST;
c.weightx = 1.0; c.weighty = 1.0;
c.insets = new Insets(0, 3, 0, 0);
((GridBagLayout)secondLine.getLayout()).setConstraints(secondButton1, c);
secondLine.add(secondButton1);

secondButton2 = new JCheckBox("schwerverletzt");
c = new GridBagConstraints();
c.gridx = 2; c.gridy = 0;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.BOTH; c.anchor = GridBagConstraints.WEST;
c.weightx = 1.0; c.weighty = 1.0;
((GridBagLayout)secondLine.getLayout()).setConstraints(secondButton2, c);
secondLine.add(secondButton2);

secondButton3 = new JCheckBox("leichtverletzt");
c = new GridBagConstraints();
c.gridx = 3; c.gridy = 0;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.BOTH; c.anchor = GridBagConstraints.WEST;
c.weightx = 1.0; c.weighty = 1.0;
c.insets = new Insets(0, 0, 0, 1);
((GridBagLayout)secondLine.getLayout()).setConstraints(secondButton3, c);
secondLine.add(secondButton3);

secondLine.setPreferredSize(new Dimension(383, 30));
c = new GridBagConstraints();
c.gridx = 0; c.gridy = 1;
c.gridwidth = 1; c.gridheight = 1;
c.fill = GridBagConstraints.HORIZONTAL; c.anchor = GridBagConstraints.WEST;
c.weightx = 1.0; c.weighty = 0.0;
c.insets = new Insets(0, 10, 10, 10);
((GridBagLayout)content.getLayout()).setConstraints(secondLine, c);
content.add(secondLine);
}

public static void main(String[] args) {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
} catch (Exception exception) {
System.out.println("WARNUNG: Unsupported L&F !!!");
}

GridBagLayoutTest test = new GridBagLayoutTest();
test.pack();
test.setLocation(50,50);
test.setVisible(true);

System.out.println("FirstLineLabel : (" + test.firstLabel.getPreferredSize().width + ", "
+ test.firstLabel.getPreferredSize().height + ")");
System.out.println("FirstLineCheckBox1 : (" + test.firstButton1.getPreferredSize().width + ", "
+ test.firstButton1.getPreferredSize().height + ")");
System.out.println("FirstLineCheckBox2 : (" + test.firstButton2.getPreferredSize().width + ", "
+ test.firstButton2.getPreferredSize().height + ")");
System.out.println("FirstLineCheckBox3 : (" + test.firstButton3.getPreferredSize().width + ", "
+ test.firstButton3.getPreferredSize().height + ")");

System.out.println("FirstLineLabel : (" + test.firstLabel.getSize().width + ", "
+ test.firstLabel.getSize().height + ")");
System.out.println("FirstLineCheckBox1 : (" + test.firstButton1.getSize().width + ", "
+ test.firstButton1.getSize().height + ")");
System.out.println("FirstLineCheckBox2 : (" + test.firstButton2.getSize().width + ", "
+ test.firstButton2.getSize().height + ")");
System.out.println("FirstLineCheckBox3 : (" + test.firstButton3.getSize().width + ", "
+ test.firstButton3.getSize().height + ")");

System.out.println("SecondLineLabel : (" + test.secondLabel.getPreferredSize().width + ", "
+ test.secondLabel.getPreferredSize().height + ")");
System.out.println("SecondLineCheckBox1 : (" + test.secondButton1.getPreferredSize().width + ", "
+ test.secondButton1.getPreferredSize().height + ")");
System.out.println("SecondLineCheckBox2 : (" + test.secondButton2.getPreferredSize().width + ", "
+ test.secondButton2.getPreferredSize().height + ")");
System.out.println("SecondLineCheckBox3 : (" + test.secondButton3.getPreferredSize().width + ", "
+ test.secondButton3.getPreferredSize().height + ")");

System.out.println("SecondLineLabel : (" + test.secondLabel.getSize().width + ", "
+ test.secondLabel.getSize().height + ")");
System.out.println("SecondLineCheckBox1 : (" + test.secondButton1.getSize().width + ", "
+ test.secondButton1.getSize().height + ")");
System.out.println("SecondLineCheckBox2 : (" + test.secondButton2.getSize().width + ", "
+ test.secondButton2.getSize().height + ")");
System.out.println("SecondLineCheckBox3 : (" + test.secondButton3.getSize().width + ", "
+ test.secondButton3.getSize().height + ")");
}

}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
A temporary workaroud would be to increase the size of one of the subcomponents by one or two pixel (for examply by adding insets).