Syntax Highlighter para el Blog

Ejemplo de muestra.
Referencia Blog

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class GUI extends JFrame implements ActionListener{
private JLabel l1, l2, l3, l4,l5;
private JTextField campo;
  private JButton ac;
private String a, b,x,x1;
private int e, f,f1;
private double g,g1;
  protected Calculo c;

public GUI(){
super ("Calcular costos");
this.ac();
this.setResizable(false);
this.setLocationRelativeTo(null);
this.setSize(250,200);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
}