How to get location of a mouse click relative to a swing window

From MouseListener methods you can do:

@Override
public void mouseClicked(MouseEvent e) {
    int x=e.getX();
    int y=e.getY();
    System.out.println(x+","+y);//these co-ords are relative to the component
}

Simply add this to your Component by:

component.addMouseListener(new MouseListener() {
    @Override
    public void mouseClicked(MouseEvent e) {
    }
});

Reference:

• How to Write a Mouse Listener

You can add MouseListener to GUI component whose top left pixel should be threated as [0,0] point, and get x and y from MouseEvent

JFrame frame = new JFrame();
JPanel panel = new JPanel();
frame.add(panel);
panel.addMouseListener(new MouseAdapter() {// provides empty implementation of all
                                           // MouseListener`s methods, allowing us to
                                           // override only those which interests us
    @Override //I override only one method for presentation
    public void mousePressed(MouseEvent e) {
        System.out.println(e.getX() + "," + e.getY());
    }
});
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200, 200);
frame.setVisible(true);

Take a look at Component.getMousePosition.

Returns the position of the mouse pointer in this Component's coordinate space if the Component is directly under the mouse pointer, otherwise returns null. If the Component is not showing on the screen, this method returns null even if the mouse pointer is above the area where the Component would be displayed. If the Component is partially or fully obscured by other Components or native windows, this method returns a non-null value only if the mouse pointer is located above the unobscured part of the Component.

final Point mousePos = component.getMousePosition();
if (mousePos != null) {
  final int mouseX = mousePos.x;
  final int mouseY = mousePos.y;
  ...
}

... or, if you use a MouseListener, you may see my original comment...

Try using MouseEvent.getPoint.

The above will return the mouse point relative to the component to which the listener was bound.

public void mouseClicked(final MouseEvent evt) {
  final Point pos = evt.getPoint();
  final int x = pos.x;
  final int y = pos.y;
}

MouseEvent has methods getX() and getY() that return the position relative to the source component.