import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class GUI {

	private JFrame frame;
	private JButton button;

	public static void main(String[] args){
		SwingUtilities.invokeLater(new Runnable(){
			public void run(){
				GUI gui = new GUI();
				gui.setup();
			}

		});
	}

	public GUI(){
		frame = new JFrame("SET COLOR");
		button = new JButton("CHANGE");
		button.addActionListener(new ColorChanged(frame));
	}

	public void setup(){
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
		frame.setSize(500,500);
		frame.setResizable(false);
		GridLayout layout = new GridLayout(7,1);
		frame.setLayout(layout);
		frame.add(button);
		frame.getContentPane().setBackground(Color.orange);
	}
/*
	class colorChanged implements ActionListener{
		public void actionPerformed(ActionEvent evt){
			frame.getContentPane().setBackground(Color.cyan);
		}
	}
	*/
}



/***************** CLASSE ESTERNA **********************/

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JFrame;



public class ColorChanged implements ActionListener {

	private JFrame frame;

	public ColorChanged(JFrame frame){
		this.frame = frame;
	}

	public void actionPerformed(ActionEvent ext){
		if(frame.getContentPane().getBackground()== Color.orange)
			frame.getContentPane().setBackground(Color.cyan);
		else
			frame.getContentPane().setBackground(Color.orange);
		}
}