Java Programming

import java.awt.Frame;
import java.awt.Button;
import java.awt.GridBagLayout;
import java.awt.GridBagConstraints;

class Program
{    public static void main(String args[])
     {    Frame MainWindow = new Frame("GridBagWindow");
          Button TestButton = new Button("TEST");
          GridBagLayout GBL = new GridBagLayout();
          GridBagConstraints GBC = new GridBagConstraints();
          
          MainWindow.setLayout(GBL);
          
          GBC.gridx=0;
          GBC.gridy=0;
          GBC.gridwidth=5;
          GBC.gridheight=5;
          GBC.weightx=1.0;
          GBC.weighty=1.0;
          MainWindow.add("TEST",TestButton);
          GBL.setConstraints(TestButton,GBC);
          
          MainWindow.show();
     }
}

I get this, when I run it:

Exception in thread "main" java.lang.IllegalArgumentException: cannot add to lay
out: constraints must be a GridBagConstraint
at java.awt.GridBagLayout.addLayoutComponent(GridBagLayout.java:608)
at java.awt.Container.addImpl(Container.java:1058)
at java.awt.Container.add(Container.java:364)
at Program.main(gblTest.java:21)

I haven't specified the "docs" folder of the GUI I'm using, JCreator. Is that very significant?