How can I create a bar in the bottom of a Java app, like a status bar?

Create a JFrame or JPanel with a BorderLayout, give it something like a BevelBorder or line border so it is seperated off from the rest of the content and then add the status panel at BorderLayout.SOUTH.

JFrame frame = new JFrame();
frame.setLayout(new BorderLayout());
frame.setSize(200, 200);

// create the status bar panel and shove it down the bottom of the frame
JPanel statusPanel = new JPanel();
statusPanel.setBorder(new BevelBorder(BevelBorder.LOWERED));
frame.add(statusPanel, BorderLayout.SOUTH);
statusPanel.setPreferredSize(new Dimension(frame.getWidth(), 16));
statusPanel.setLayout(new BoxLayout(statusPanel, BoxLayout.X_AXIS));
JLabel statusLabel = new JLabel("status");
statusLabel.setHorizontalAlignment(SwingConstants.LEFT);
statusPanel.add(statusLabel);

frame.setVisible(true);

Here is the result of the above status bar code on my machine:

Unfortunately Swing does not have a native support for StatusBars. You can use a BorderLayout and a label or whatever you need to display at the bottom:

public class StatusBar extends JLabel {

    /** Creates a new instance of StatusBar */
    public StatusBar() {
        super();
        super.setPreferredSize(new Dimension(100, 16));
        setMessage("Ready");
    }

    public void setMessage(String message) {
        setText(" "+message);        
    }        
}

Then in your Main Panel:

statusBar = new StatusBar();
getContentPane().add(statusBar, java.awt.BorderLayout.SOUTH);

From: http://www.java-tips.org/java-se-tips/javax.swing/creating-a-status-bar.html

I have used swing library from L2FProd. The Status bar library they have provided is very good.

Below is how you would use it:

1. Download the JAR they are providing and put it in your classpath

2. The status bar internally divides the bar area into zone. Each zone can contain a Component (JLabel, JButton, etc). Idea is to fill the bar with required zones and the components.

3. Instantiate the status bar as below....

   import java.awt.Component;
   import javax.swing.BorderFactory;
   import javax.swing.JLabel;
   import com.l2fprod.common.swing.StatusBar;
   
   StatusBar statusBar = new StatusBar();
   statusBar.setZoneBorder(BorderFactory.createLineBorder(Color.GRAY));
   statusBar.setZones(
       new String[] { "first_zone", "second_zone", "remaining_zones" },
       new Component[] {
           new JLabel("first"),
           new JLabel("second"),
           new JLabel("remaining")
       },
       new String[] {"25%", "25%", "*"}
   );
   

4. Now add the above statusBar to the main panel you have (BorderLayout and set it to the south side).

See a sample screenshot from one of the apps I am working on here (it has 2 zones). Let me know if you face any issues....

I would recommend the status bar component in the SwingX library - Here is the API doc for the status bar is here

A good example of its use is here.

Have fun.

For a more modern look than the accepted answer go with a GridBagLayout and a JSeparator:

JPanel outerPanel = new JPanel(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.anchor = GridBagConstraints.PAGE_START;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weightx = 1;
gbc.weighty = 0;

JPanel menuJPanel = new JPanel();
menuJPanel.setBorder(BorderFactory.createMatteBorder(1, 1, 1, 1, Color.RED));
outerPanel.add(menuJPanel, gbc);

gbc.insets = new Insets(5, 5, 5, 5);
gbc.fill = GridBagConstraints.BOTH;
gbc.weighty = 1;

JPanel contentJPanel = new JPanel();
contentJPanel.setBorder(BorderFactory.createMatteBorder(1, 1, 1, 1, Color.BLUE));
outerPanel.add(contentJPanel, gbc);

gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weighty = 0;
gbc.insets = new Insets(0, 0, 0, 0);

outerPanel.add(new JSeparator(JSeparator.HORIZONTAL), gbc);
outerPanel.add(new JPanel(), gbc);