Sourcecode Kalkulator Sederhana (Java on NetBeans)

Sedikit share source code untuk membuat kalkulator. Tampilannya kira-kira seperti ini:

Tapi masih banyak kekurangannya, jadi mohon koreksinya
/*
* Kalkulator.java
*
* Created on March 26, 2011, 8:22 PM
*/

package kalkulator_sederhana;

/**
*
* @author cursedcode
*/
public class Kalkulator extends javax.swing.JFrame {
String angka;
Double total,angka1,angka2;
int pilih;
/** Creates new form Kalkulator */
public Kalkulator() {
initComponents();
angka="";
}

/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.

Hello world!

class StartingNew {
    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}