How can I get screen resolution in java?

You can get the screen size with the Toolkit.getScreenSize() method.

Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
double width = screenSize.getWidth();
double height = screenSize.getHeight();

On a multi-monitor configuration you should use this :

GraphicsDevice gd = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();
int width = gd.getDisplayMode().getWidth();
int height = gd.getDisplayMode().getHeight();

If you want to get the screen resolution in DPI you'll have to use the getScreenResolution() method on Toolkit.

Resources :

• javadoc - Toolkit.getScreenSize()
• Java bug 5100801- Toolkit.getScreenSize() does not return the correct dimension on multimon, linux

This code will enumerate the graphics devices on the system (if multiple monitors are installed), and you can use that information to determine monitor affinity or automatic placement (some systems use a little side monitor for real-time displays while an app is running in the background, and such a monitor can be identified by size, screen colors, etc.):

// Test if each monitor will support my app's window
// Iterate through each monitor and see what size each is
GraphicsEnvironment ge      = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice[]    gs      = ge.getScreenDevices();
Dimension           mySize  = new Dimension(myWidth, myHeight);
Dimension           maxSize = new Dimension(minRequiredWidth, minRequiredHeight);
for (int i = 0; i < gs.length; i++)
{
    DisplayMode dm = gs[i].getDisplayMode();
    if (dm.getWidth() > maxSize.getWidth() && dm.getHeight() > maxSize.getHeight())
    {   // Update the max size found on this monitor
        maxSize.setSize(dm.getWidth(), dm.getHeight());
    }

    // Do test if it will work here
}

This call will give you the information you want.

Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

Here's some functional code (Java 8) which returns the x position of the right most edge of the right most screen. If no screens are found, then it returns 0.

  GraphicsDevice devices[];

  devices = GraphicsEnvironment.
     getLocalGraphicsEnvironment().
     getScreenDevices();

  return Stream.
     of(devices).
     map(GraphicsDevice::getDefaultConfiguration).
     map(GraphicsConfiguration::getBounds).
     mapToInt(bounds -> bounds.x + bounds.width).
     max().
     orElse(0);

Here are links to the JavaDoc.

GraphicsEnvironment.getLocalGraphicsEnvironment()
GraphicsEnvironment.getScreenDevices()
GraphicsDevice.getDefaultConfiguration()
GraphicsConfiguration.getBounds()