How do I read the status of Caps Lock key?

By Wayan in AWT, Core API 0 Comment

This example show you how to detect if the Caps Lock key is in active mode.

package org.kodejava.awt;

import java.awt.Toolkit;
import java.awt.event.KeyEvent;

public class CapsLockState {
    public static void main(String[] args) {
        // Get the locking state of the Caps Lock button. This method
        // return boolean true value if it is "on".
        boolean isOn = Toolkit.getDefaultToolkit().getLockingKeyState(
                KeyEvent.VK_CAPS_LOCK);

        System.out.println("CapsLock button is " + (isOn ? "on" : "off"));
    }
}

How do I get my screen size?

By Wayan in AWT, Core API 0 Comment 
package org.kodejava.awt;

import java.awt.*;

public class ScreenSizeExample {
    public static void main(String[] args) {
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

        System.out.println("Screen Width: " + screenSize.getWidth());
        System.out.println("Screen Height: " + screenSize.getHeight());
    }
}

The output of the code snippet above:

Screen Width: 2560.0
Screen Height: 1080.0

How do I make a centered JFrame?

By Wayan in Swing 0 Comment

If you have a JFrame in your Java Swing application and want to center its position on the screen you can use the following code snippets.

The first way is to utilize java.awt.Toolkit class to get the screen size. The getScreenSize() method return a java.awt.Dimension from where we can get the width and height of the screen. Having this values in hand we can calculate the top left position of our JFrame as shown in step 2 of the code below.

package org.kodejava.swing;

import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import java.awt.Dimension;
import java.awt.Toolkit;

public class CenteredJFrame extends JFrame {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            // 1. Get the size of the screen
            Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

            CenteredJFrame frame = new CenteredJFrame();
            frame.setTitle("Centered JFrame");
            frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            frame.setSize(500, 500);

            // 2. Calculates the position where the CenteredJFrame
            // should be paced on the screen.
            int x = (screenSize.width - frame.getWidth()) / 2;
            int y = (screenSize.height - frame.getHeight()) / 2;
            frame.setLocation(x, y);
            frame.setVisible(true);
        });
    }
}

The second way which is better and simpler is to use the setLocationRelativeTo(Component) method. According to the Java API documentation of this method: If the component is null, or the GraphicsConfiguration associated with this component is null, the window is placed in the center of the screen.

If you call the JFrame.pack() method. The method should be called before the setLocationRelativeTo() method.

So we can rewrite the code above like this:

package org.kodejava.swing;

import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;

public class CenteredJFrameSecond {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            CenteredJFrame frame = new CenteredJFrame();
            frame.setTitle("Centered JFrame");
            frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            frame.setSize(500, 500);

            // Place the window in the center of the screen.
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        });
    }
}

How do I create a beep sound?

By Wayan in AWT, Core API 0 Comment 
package org.kodejava.awt;

import java.awt.*;

public class BeepExample {
    public static void main(String[] args) {
        // This is the way we can send a beep audio out.
        Toolkit.getDefaultToolkit().beep();
    }
}

Using Runtime.exec() method we can do something like the code snippet below to produce beep sound using powershell command.

try {
    Process process = Runtime.getRuntime().exec(
            new String[]{"powershell", "[console]::beep()"});

    int errorCode = process.waitFor();
    int exitValue = process.exitValue();
    System.out.println("errorCode = " + errorCode);
    System.out.println("exitValue = " + exitValue);
} catch (Exception e) {
    throw new RuntimeException(e);
}

We can also execute external command using ProcessBuilder class like the following code snippet:

try {
    ProcessBuilder processBuilder = new ProcessBuilder();
    processBuilder.command("powershell", "[console]::beep()");
    Process process = processBuilder.start();

    int errorCode = process.waitFor();
    int exitValue = process.exitValue();
    System.out.println("errorCode = " + errorCode);
    System.out.println("exitValue = " + exitValue);
} catch (Exception e) {
    throw new RuntimeException(e);
}