Swing UI differs between Linux & Windows. How to fix?

Question

I'm having some difficulties with the different look between OSes.
Well the main problem is not that it looks different but
that in linux the controls are bigger so that some controls don't fit in the window anymore:
Linux
Windows
Since I have basically mo experience with crossplatform & GUI applications,
I'm blindly trying to fix this but to no avail.
How can I correct this behaviour so it looks more like it does in Windows?
Relevant code:
JButton bFile=new JButton("Add File");
JButton bDir=new JButton("Add Dir");
JButton bRenamePattern=new JButton("Rename Config");
JPanel lowerPanel = new javax.swing.JPanel(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
c.gridx=0; c.gridy=0;
c.gridwidth = GridBagConstraints.REMAINDER;
lowerPanel.add(prgbr_Progress[0],c); c.gridy++;
lowerPanel.add(prgbr_Progress[1],c); c.gridy++;
JPanel innerPanel = new javax.swing.JPanel(new GridBagLayout());
GridBagConstraints cInner = new GridBagConstraints();
cInner.gridx=0; cInner.gridy=0;
cInner.fill = GridBagConstraints.HORIZONTAL;
cInner.weightx = 1;
innerPanel.add(lblProcessedMB, cInner); cInner.gridx++;
innerPanel.add(lblTimeElapsed, cInner); cInner.gridx++;
innerPanel.add(lblTimeRemaining, cInner); cInner.gridx++;
lowerPanel.add(innerPanel,c); c.gridy++;
c.gridwidth=1;
c.weightx=0; lowerPanel.add(withLabel("Set state",comboState),c);
c.weightx=0; c.gridx++; lowerPanel.add(checkFilesWatched,c);
c.gridx++; lowerPanel.add(checkRenameFiles,c);
c.gridx++; lowerPanel.add(bRenamePattern,c);
c.gridx++; lowerPanel.add(bFile,c);
c.gridx++; lowerPanel.add(bDir,c);
c.gridx++; lowerPanel.add(bRemove,c);
c.gridwidth = GridBagConstraints.REMAINDER;
c.gridx++; lowerPanel.add(bStart,c);
setLayout(new BorderLayout());
add(scrollPane,BorderLayout.CENTER);
add(lowerPanel,BorderLayout.SOUTH);

Answer 1

BoBear2681:
I can't confirm that.
The size is the same on both systems 800x600.
And if you look closely to both pictures you'll see that the font is slightly bigger on the linux system (and more spacing).
Also easlily noticable is the JTable, the entries there doesn't fit height wise (the text is capped of at the top).
Another thing is that the last row of the controls (bottom), the height is much greater.
AndrewThompson64
I also made it SSCCE:
//Applett
import javax.swing.JApplet;
@SuppressWarnings("serial")
public class Main extends JApplet {
    public static boolean runsLocally=false;
    public GUI GUI;
    public void init(){
        GUI = new GUI();
    public void start(){
         setSize(800, 600);
          add(GUI);
          System.out.println("Started");
//GUI Class
import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.*;
//Applet user interface
@SuppressWarnings("serial")
public class GUI extends javax.swing.JPanel {
    private final JProgressBar[] prgbr_Progress = new JProgressBar[] {new JProgressBar(), new JProgressBar()};
    public final JCheckBox checkFilesWatched = new javax.swing.JCheckBox("Mark Watched");
    public final JCheckBox checkRenameFiles = new javax.swing.JCheckBox("Rename Files");
    private final JComboBox comboState = new javax.swing.JComboBox();
    private final JButton bStart = new JButton("Start");
    private final JButton bRemove = new JButton("Remove");
    private final JLabel lblProcessedMB = new JLabel("0 of 0 MB processed", JLabel.CENTER);
    private final JLabel lblTimeElapsed = new JLabel("Time elapsed: 0:00:00", JLabel.CENTER);
    private final JLabel lblTimeRemaining = new JLabel("Time remaining: 0:00:00", JLabel.CENTER);
    public GUI() {
        comboState.setModel(new javax.swing.DefaultComboBoxModel(new String[] {"Unknown", "On HDD", "OnCD", "Deleted" })); //currently relying on item order
        comboState.setSelectedIndex(1);
        JScrollPane scrollPane = new javax.swing.JScrollPane();
        scrollPane.setViewportView(new javax.swing.JTable());
        JButton bFile=new JButton("Add File");
        JButton bDir=new JButton("Add Dir");
        JButton bRenamePattern=new JButton("Rename Config");
        JPanel lowerPanel = new javax.swing.JPanel(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        c.fill = GridBagConstraints.HORIZONTAL;
        c.gridx=0; c.gridy=0;
        c.gridwidth = GridBagConstraints.REMAINDER;
        lowerPanel.add(prgbr_Progress[0],c); c.gridy++;
        lowerPanel.add(prgbr_Progress[1],c); c.gridy++;
        JPanel innerPanel = new javax.swing.JPanel(new GridBagLayout());
        GridBagConstraints cInner = new GridBagConstraints();
        cInner.gridx=0; cInner.gridy=0;
        cInner.fill = GridBagConstraints.HORIZONTAL;
        cInner.weightx = 1;
        innerPanel.add(lblProcessedMB, cInner); cInner.gridx++;
        innerPanel.add(lblTimeElapsed, cInner); cInner.gridx++;
        innerPanel.add(lblTimeRemaining, cInner); cInner.gridx++;
        lowerPanel.add(innerPanel,c); c.gridy++;
        c.gridwidth=1;
        c.weightx=0; lowerPanel.add(withLabel("Set state",comboState),c);
        c.weightx=0; c.gridx++; lowerPanel.add(checkFilesWatched,c);
        c.gridx++; lowerPanel.add(checkRenameFiles,c);
        c.gridx++; lowerPanel.add(bRenamePattern,c);
        c.gridx++; lowerPanel.add(bFile,c);
        c.gridx++; lowerPanel.add(bDir,c);
        c.gridx++; lowerPanel.add(bRemove,c);
        c.gridwidth = GridBagConstraints.REMAINDER;
        c.gridx++; lowerPanel.add(bStart,c);
        setLayout(new BorderLayout());
        add(scrollPane,BorderLayout.CENTER);
        add(lowerPanel,BorderLayout.SOUTH);
        validate();
    //Add a label to the left of a swing component
    public static JPanel withLabel(String s, JComponent c){
        JPanel p=new JPanel(new BorderLayout());
        p.add(new JLabel(s),BorderLayout.WEST);
        p.add(c,BorderLayout.CENTER);
        return p;
}I'll try your suggestions,
I'll post the results if I have them.