Tela em Java

package pacote;

import javax.swing.*;
import java.awt.*;

public class Tela extends JFrame {
	
	private Container container;
	private JButton botao;
	private LayoutManager layout;
	
	public Tela() {
		container = this.getContentPane();
		layout = new FlowLayout(FlowLayout.CENTER);
		container.setLayout(layout);
		botao = new JButton("Processar");
		container.add(botao);
		this.setSize(300,300);
		this.setVisible(true);
	}
	
	public static void main(String args[]) {
		Tela tela = new Tela();
		tela.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}

}