Java JFrame Size according to screen resolution

I created java GUI using myEclipse Matisse. when my Screen Resolution is 1024x768 it works fine but when i change resolution my GUI is not working fine. I want my GUI window should be re-sized according to the screen Resolution I am extending JFrame to create the main window.

public class MyClass extends JFrame {

    //I am putting some controls here.

    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    setBounds(0,0,screenSize.width, screenSize.height);
    setVisible(true);

    pack();
}

this is not working, what ever i do, setting size hardcoded or by ToolKit using, the Frame Size Remains same.