COMO HACER CALCULADORA EN NETBEANS

import javax.swing.JButton;

/*

* To change this template, choose Tools | Templates

* and open the template in the editor.

*/

/**

*

* @author PC-14

*/

public class calculadorass extends javax.swing.JFrame {

private JButton M;

private JButton N;

private JButton MUL;

private JButton IGU;

private JButton DIV;

String memoria1;

String signo;

String memoria2;

/**

* Creates new form calculadorass

*/

public calculadorass() {

initComponents();

}

/**

* 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.

*/

@SuppressWarnings("unchecked")

// <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents

private void initComponents() {

jPanel1 = new javax.swing.JPanel();

NUM1 = new javax.swing.JButton();

NUM4 = new javax.swing.JButton();

NUM7 = new javax.swing.JButton();

PUNTO = new javax.swing.JButton();

NUM2 = new javax.swing.JButton();

NUM5 = new javax.swing.JButton();

NUM8 = new javax.swing.JButton();

NUM0 = new javax.swing.JButton();

NUM3 = new javax.swing.JButton();

NUM6 = new javax.swing.JButton();

NUM9 = new javax.swing.JButton();

IGUAL = new javax.swing.JButton();

MAS = new javax.swing.JButton();

MENOS = new javax.swing.JButton();

MULTI = new javax.swing.JButton();

DIVICION = new javax.swing.JButton();

MOSTRADOR = new javax.swing.JLabel();

CLEAR = new javax.swing.JButton();

C = new javax.swing.JButton();

BARRAMENU = new javax.swing.JMenuBar();

jMenu1 = new javax.swing.JMenu();

jMenuItem1 = new javax.swing.JMenuItem();

jMenu2 = new javax.swing.JMenu();

jMenuItem2 = new javax.swing.JMenuItem();

jMenu4 = new javax.swing.JMenu();

jMenuItem3 = new javax.swing.JMenuItem();

jMenu5 = new javax.swing.JMenu();

jMenuItem4 = new javax.swing.JMenuItem();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

NUM1.setBackground(new java.awt.Color(153, 153, 153));

NUM1.setForeground(new java.awt.Color(51, 51, 51));

NUM1.setText("1");

NUM1.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

NUM1ActionPerformed(evt);

}

});

NUM4.setBackground(new java.awt.Color(153, 153, 153));

NUM4.setForeground(new java.awt.Color(51, 51, 51));

NUM4.setText("4");

NUM4.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

NUM4ActionPerformed(evt);

}

});

NUM7.setBackground(new java.awt.Color(153, 153, 153));

NUM7.setForeground(new java.awt.Color(51, 51, 51));

NUM7.setText("7");

NUM7.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

NUM7ActionPerformed(evt);

}

});

PUNTO.setBackground(new java.awt.Color(153, 153, 153));

PUNTO.setForeground(new java.awt.Color(51, 51, 51));

PUNTO.setText(".");

PUNTO.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

PUNTOActionPerformed(evt);

}

});

NUM2.setBackground(new java.awt.Color(153, 153, 153));

NUM2.setForeground(new java.awt.Color(51, 51, 51));

NUM2.setText("2");

NUM2.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

NUM2ActionPerformed(evt);

}

});

NUM5.setBackground(new java.awt.Color(153, 153, 153));

NUM5.setForeground(new java.awt.Color(51, 51, 51));

NUM5.setText("5");

NUM5.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

NUM5ActionPerformed(evt);

}

});

NUM8.setBackground(new java.awt.Color(153, 153, 153));

NUM8.setForeground(new java.awt.Color(51, 51, 51));

NUM8.setText("8");

NUM8.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

NUM8ActionPerformed(evt);

}

});

NUM0.setBackground(new java.awt.Color(153, 153, 153));

NUM0.setForeground(new java.awt.Color(51, 51, 51));

NUM0.setText("0");

NUM0.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

NUM0ActionPerformed(evt);

}

});

NUM3.setBackground(new java.awt.Color(153, 153, 153));

NUM3.setForeground(new java.awt.Color(51, 51, 51));

NUM3.setText("3");

NUM3.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

NUM3ActionPerformed(evt);

}

});

NUM6.setBackground(new java.awt.Color(153, 153, 153));

NUM6.setForeground(new java.awt.Color(51, 51, 51));

NUM6.setText("6");

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