Develop Reference

How can I display a java frame using an itemListener? [duplicate]

I am trying to do a simple Jform and call it from another class.
I want to use this Jframe in a server client application, but I don't know how to open the JFrame class from another class.
Like user has to chose
1- to open Jframe.
2- To Exit.
So What am I doing wrong?
Below are the codes:
Jframe Class named Calculas.java
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
/**
*
* #author user
*/
public class Calculas extends javax.swing.JFrame {
/**
* Creates new form Calculas
*/
public Calculas() {
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">
private void initComponents() {
a1Text = new javax.swing.JTextField();
a2Text = new javax.swing.JTextField();
jLabel1 = new javax.swing.JLabel();
jButton1 = new javax.swing.JButton();
answer = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jButton1.setText("jButton1");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(a1Text, javax.swing.GroupLayout.PREFERRED_SIZE, 43, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(a2Text, javax.swing.GroupLayout.PREFERRED_SIZE, 97, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(87, 87, 87)
.addComponent(answer, javax.swing.GroupLayout.PREFERRED_SIZE, 67, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addGap(113, 113, 113)
.addComponent(jLabel1))
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jButton1)))
.addContainerGap(86, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(19, 19, 19)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(a1Text, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(a2Text, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addComponent(answer, javax.swing.GroupLayout.PREFERRED_SIZE, 24, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(60, 60, 60)
.addComponent(jLabel1)
.addGap(34, 34, 34)
.addComponent(jButton1)
.addContainerGap(140, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
int a;
a = Integer.parseInt(a1Text.getText()) + Integer.parseInt(a2Text.getText());
answer.setText("Answer" + a);
// TODO add your handling code here:
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Calculas().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JTextField a1Text;
private javax.swing.JTextField a2Text;
private javax.swing.JLabel answer;
private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel1;
// End of variables declaration
}
Test Class named Test.java
public class Test extends JFrame {
public static void main(String args[])
{
Calculas CAL = new Calculas();
CAL.Calculus();
}
}

Forgive me if this is naive, as Im not anything of a Java programmer...
But isnt it just because you need to set visible?
Calculas CAL = new Calculas();
CAL.setVisible(true);

The constructor of Calculas doesn't show (setVisible) the frame.
If you want to interact with the Calculas class in this manner, you should also be calling CAL.setVisible(true)
Also, by convention, all Java instance variables, should start with a lower case character and use camelCase conventions

In it's current form of your code, you can call the main method of your Calculas class in Test class or move the code to the Test class.
Warning: Extending JFrame is not a good Idea.
First alternative: You don't need to extend JFrame in Test
public class Test{
public static void main(String args[])
{
Calculas.main(new String[0]);
}
}
You haven't mentioned in your question how you want to be able to chose close or open, in console or in another JFrame or something...
Second Alternative:
But If I were you I could do something like this: wrap the code for look and feel in a separate method and call this from Test' s main.
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
/**
*
* #author user
*/
public class Calculas extends javax.swing.JFrame {
/**
* Creates new form Calculas
*/
public Calculas() {
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">
private void initComponents() {
a1Text = new javax.swing.JTextField();
a2Text = new javax.swing.JTextField();
jLabel1 = new javax.swing.JLabel();
jButton1 = new javax.swing.JButton();
answer = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jButton1.setText("jButton1");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(a1Text, javax.swing.GroupLayout.PREFERRED_SIZE, 43, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(a2Text, javax.swing.GroupLayout.PREFERRED_SIZE, 97, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(87, 87, 87)
.addComponent(answer, javax.swing.GroupLayout.PREFERRED_SIZE, 67, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addGap(113, 113, 113)
.addComponent(jLabel1))
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jButton1)))
.addContainerGap(86, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(19, 19, 19)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(a1Text, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(a2Text, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addComponent(answer, javax.swing.GroupLayout.PREFERRED_SIZE, 24, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(60, 60, 60)
.addComponent(jLabel1)
.addGap(34, 34, 34)
.addComponent(jButton1)
.addContainerGap(140, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
int a;
a = Integer.parseInt(a1Text.getText()) + Integer.parseInt(a2Text.getText());
answer.setText("Answer" + a);
// TODO add your handling code here:
}
public static setNimbusFeel(){
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
}
// Variables declaration - do not modify
private javax.swing.JTextField a1Text;
private javax.swing.JTextField a2Text;
private javax.swing.JLabel answer;
private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel1;
// End of variables declaration
}
And test class like this:
public class Test{
public static void main(String args[])
{
Calculas cal=new Calculas();
//</editor-fold>
Calculas.setNimbusFeel();
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Calculas().setVisible(true);
}
});
}
}
Like this:

Here's an example of a basic structure you can use:
import java.awt.*;
import javax.swing.*;
class MyGui {
private JFrame window = new JFrame("This is the title");
public MyGui() {
initComponents();
window.setBounds(100, 50, 600, 400); //location, size
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setVisible(true);
}
public void initComponents() {
Container cp = window.getContentPane();
cp.setLayout(new FlowLayout() );
cp.add(new JLabel("Hello world") );
}
}
public class MyProg {
private static void createAndShowGUI() {
new MyGui();
}
public static void main(String[] args) {
//Schedule a job for the event dispatch thread:
//creating and showing this application's GUI.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
And in separate files:
MyGui.java
import java.awt.*;
import javax.swing.*;
public class MyGui {
private JFrame window = new JFrame("This is the title");
public MyGui() {
initComponents();
window.setBounds(100, 50, 600, 400); //location, size
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setVisible(true);
}
public void initComponents() {
Container cp = window.getContentPane();
cp.setLayout(new FlowLayout() );
cp.add(new JLabel("Hello world") );
}
}
MyProg.java
import javax.swing.*;
public class MyProg {
private static void createAndShowGUI() {
new MyGui();
}
public static void main(String[] args) {
//Schedule a job for the event dispatch thread:
//creating and showing this application's GUI.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}

Calculas CAL = new Calculas();
CAL.Calculus();
maybe, CAL.Calculas(); I dont know java but I realized that, sorry about my english:)

GUI wont display

public class NewClass extends javax.swing.JFrame {
/**
* Creates new form NewClass
*/
public NewClass() {
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">
private void initComponents() {
jScrollPane1 = new javax.swing.JScrollPane();
jTextArea1 = new javax.swing.JTextArea();
jButton1 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jTextArea1.setColumns(20);
jTextArea1.setRows(5);
jScrollPane1.setViewportView(jTextArea1);
jButton1.setText("jButton1");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(82, 82, 82)
.addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 583, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addGap(285, 285, 285)
.addComponent(jButton1)))
.addContainerGap(60, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(39, Short.MAX_VALUE)
.addComponent(jButton1)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 506, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(50, 50, 50))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(NewClass.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewClass.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewClass.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewClass.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new NewClass().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextArea jTextArea1;
// End of variables declaration
Guys this is the first time I try to create a GUI from Netbeans generator, there is not compilation error but nothing shows pops up. This is not my code is the code auto generated after creating the design part. However I tried manually same no compilation error but nothing pops up
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package assigment1;
import java.awt.*;
import javax.swing.*;
public class RectangleProgram extends JFrame
{
private static final int WIDTH = 400;
private static final int HEIGHT = 300;
private JLabel lengthL, widthL, areaL, perimeterL;
private JTextField lengthTF, widthTF, areaTF, perimeterTF;
private JButton calculateB, exitB;
public RectangleProgram()
{
//Instantiate the labels:
lengthL = new JLabel("Enter the length: ", SwingConstants.RIGHT);
widthL = new JLabel("Enter the width: ", SwingConstants.RIGHT);
areaL = new JLabel("Area: ", SwingConstants.RIGHT);
perimeterL = new JLabel("Perimeter: ", SwingConstants.RIGHT);
//Text fields next:
lengthTF = new JTextField(10);
widthTF = new JTextField(10);
areaTF = new JTextField(10);
perimeterTF = new JTextField(10);
//Buttons too:
calculateB = new JButton("Calculate");
exitB = new JButton("Exit");
//Set the window's title.
setTitle("Sample Title: Area of a Rectangle");
//Get the content pane (CP).
Container pane = getContentPane();
//Set the layout.
pane.setLayout(new GridLayout(5, 2));
//Other JFrame stuff.
setSize(WIDTH, HEIGHT);
setVisible(true);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}
This is another example code that wont pop up or show any error message, this is the first time that a use NetBeans in this computer, is a new Computer by the way.
What to do :(.

Adding element in Java Netbeans generated combo box

I'm having some problem in adding new elements to the combo box. The code is created by Netbeans Form Editor, because of this I only have access to modify the event listeners. The elements cant be predefined because the elements are in a database and constantly expanding. Currently the combo box has only one element and i would like it to update according to the values from the database. Thank you for your time folks.
package Interface;
/**
*
* #author Raam
*/
public class Welcome extends javax.swing.JFrame {
/**
* Creates new form Welcome
*/
public Welcome() {
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">
private void initComponents() {
jComboBox1 = new javax.swing.JComboBox();
jComboBox2 = new javax.swing.JComboBox();
jButton1 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("addNewRecord");
jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Add New Record", "Class", "Section", "Student" }));
jComboBox1.setToolTipText("Add New Record");
jComboBox1.setName("AddNewRecord"); // NOI18N
jComboBox1.addFocusListener(new java.awt.event.FocusAdapter() {
public void focusGained(java.awt.event.FocusEvent evt) {
jComboBox1FocusGained(evt);
}
});
jComboBox2.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Choose Class" }));
jComboBox2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jComboBox2ActionPerformed(evt);
}
});
jButton1.setText("Open Database");
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(51, 51, 51)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jButton1)
.addGroup(layout.createSequentialGroup()
.addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, 106, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(41, 41, 41)
.addComponent(jComboBox2, javax.swing.GroupLayout.PREFERRED_SIZE, 116, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addContainerGap(86, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(45, 45, 45)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jComboBox2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(jButton1)
.addContainerGap(16, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jComboBox2ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}
private void jComboBox1FocusGained(java.awt.event.FocusEvent evt) {
jComboBox1.addElement(); //Tried this, not working
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Welcome.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Welcome.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Welcome.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Welcome.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Welcome().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JComboBox jComboBox1;
private javax.swing.JComboBox jComboBox2;
// End of variables declaration
}

You have to add the ítem in the model:
DefaultComboBoxModel model = (DefaultComboBoxModel) jComboBox1.getModel();
model.addElement("new ítem");

Can be done by going to properties of the combo box then to >> model. As the answer provided here https://stackoverflow.com/a/39689417/5737654

How to take values from 10 textFields and using one button to output the choices into a textField or Area? (With code)

We're trying to design a set of Textfields where users can enter a value depending on how much quantity of the product they want. We have one button called checkout.
Basically, 2 classes, One called FoodDept (where all the textfields are and the checkout Button), and one called Checkout where there is a textfield or Area where i can output the choices or numbers the user indicated. That is basicallly all I need.
package shopping;
import java.util.*;
public class foodDept extends javax.swing.JFrame {
/**
* Creates new form foodDept
*/
int apple;
int banana;
double a = 0;
double b = 0;
public foodDept() {
initComponents();
apple=0;
banana=0;
}
/**
* 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">
private void initComponents() {
appleLabel = new javax.swing.JLabel();
appleField = new javax.swing.JTextField();
backBtn = new javax.swing.JButton();
bananaLabel = new javax.swing.JLabel();
bananaField = new javax.swing.JTextField();
checkoutBtn = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
appleLabel.setText("Apple ($1.99):");
appleField.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
appleFieldActionPerformed(evt);
}
});
backBtn.setText("Back");
backBtn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
backBtnActionPerformed(evt);
}
});
bananaLabel.setText("Banana ($0.99):");
checkoutBtn.setText("jButton1");
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(backBtn)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 152, Short.MAX_VALUE)
.addComponent(checkoutBtn))
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addGroup(layout.createSequentialGroup()
.addComponent(appleLabel)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(appleField))
.addGroup(layout.createSequentialGroup()
.addComponent(bananaLabel)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(bananaField, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addGap(0, 0, Short.MAX_VALUE)))
.addContainerGap())
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(appleLabel)
.addComponent(appleField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(bananaLabel)
.addComponent(bananaField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 59, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(backBtn)
.addComponent(checkoutBtn))
.addContainerGap())
);
pack();
}// </editor-fold>
private void backBtnActionPerformed(java.awt.event.ActionEvent evt) {
new dept().setVisible(true);
dispose();
}
void setApple(int a){
apple=a;
}
int getApple(){
return apple;
}
public double getTotal(){
return a+b;
}
private void appleFieldActionPerformed(java.awt.event.ActionEvent evt) {
}
public void checkoutBtnActionPerformed(java.awt.event.ActionEvent evt) {
try{
double priceOfapple = 1.99;
int quantity = Integer.parseInt(appleField.getText());
double totalamount = priceOfapple*quantity;
checkout.resultField.setText(totalamount);
}
b = Double.parseDouble(bananaField.getText());
foodList fL = new foodList(apple,banana);
if(a > 0){
a=a*1.99;
}
if(b > 0){
b=b*0.99;
}
new checkout().setVisible(true);
dispose();
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(foodDept.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(foodDept.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(foodDept.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(foodDept.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
//ArrayList<Double> orderList = new ArrayList<Double>();//ARRAYYYYY
//here
//for(int x = 0; x<= orderList.size();x++){
//}
foodDept a = new foodDept();
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new foodDept().setVisible(true);
}
});
}
// Variables declaration - do not modify
public javax.swing.JTextField appleField;
private javax.swing.JLabel appleLabel;
private javax.swing.JButton backBtn;
private javax.swing.JTextField bananaField;
private javax.swing.JLabel bananaLabel;
public javax.swing.JButton checkoutBtn;
// End of variables declaration
}
**********************************************************************************
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package shopping;
import java.util.ArrayList;
import shopping.foodDept;
import shopping.foodDept;
import shopping.foodDept;
/**
*
* #author Kevin
*/
public class checkout extends javax.swing.JFrame {
/**
* Creates new form checkout
*/
public checkout() {
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">
private void initComponents() {
backBtn = new javax.swing.JButton();
purchaseBtn = new javax.swing.JButton();
resultField = new javax.swing.JTextField();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
backBtn.setText("Back");
backBtn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
backBtnActionPerformed(evt);
}
});
purchaseBtn.setText("Purchase");
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(resultField)
.addGroup(layout.createSequentialGroup()
.addComponent(backBtn)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 148, Short.MAX_VALUE)
.addComponent(purchaseBtn)))
.addContainerGap())
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(resultField, javax.swing.GroupLayout.DEFAULT_SIZE, 89, Short.MAX_VALUE)
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(purchaseBtn)
.addComponent(backBtn))
.addContainerGap())
);
pack();
}// </editor-fold>
private void backBtnActionPerformed(java.awt.event.ActionEvent evt) {
new foodDept().setVisible(true);
dispose();
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(checkout.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(checkout.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(checkout.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(checkout.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
//for(int x = 0; x<= orderList.size();x++){
//resultField.setText(orderList.get(x));
//}
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new checkout().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton backBtn;
private javax.swing.JButton purchaseBtn;
public javax.swing.JTextField resultField;
// End of variables declaration
}

Before start, some off-topic advices:
Please read about Java Code
Conventions
and stick to them because they make your code more readable.
Try to make your GUI classes without using GUI builders and spend some time learning about Swing and writing your classes by your own hand. You'll learn lot of things that builder "hides" you and your code will be simpler and cleaner.
Every Swing application should have only one JFrame. Take a look to this topic: The Use of Multiple JFrames, Good/Bad Practice?
I suspect because of backBtn presence that you're trying to do a kind of wizard. If this is the case I'd suggest you take a look to CardLayout. There are plenty of examples in SO too.
Well the two classes needed are there, you just have to find out the way to communicate them. One approach would be passing a List<String> to the Checkout class so when the JTextArea is initialized it can take this list as data:
public class Checkout extends JDialog {
List<String> dataToBeDisplayed;
...
public void setDataToBeDisplayed(List<String> data) {
this.dataToBeDisplayed = data;
}
private void initComponents() {
JTextArea textArea = new JTextArea(20,30);
for(String line : dataToBeDisplayed) {
textArea.append(line + System.lineSeparator());
}
getContentPane().add(new JScrollPane(textArea));
}
}
The List must be set before the dialog becomes visible, just like this:
Checkout checkout = new Checkout(this, true);
checkout.setDataToBeDisplayed(data); // data must be created and populated before this call
checkout.setVisible(true);

How To Call JFrame from another Java class

I am trying to do a simple Jform and call it from another class.
I want to use this Jframe in a server client application, but I don't know how to open the JFrame class from another class.
Like user has to chose
1- to open Jframe.
2- To Exit.
So What am I doing wrong?
Below are the codes:
Jframe Class named Calculas.java
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
/**
*
* #author user
*/
public class Calculas extends javax.swing.JFrame {
/**
* Creates new form Calculas
*/
public Calculas() {
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">
private void initComponents() {
a1Text = new javax.swing.JTextField();
a2Text = new javax.swing.JTextField();
jLabel1 = new javax.swing.JLabel();
jButton1 = new javax.swing.JButton();
answer = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jButton1.setText("jButton1");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(a1Text, javax.swing.GroupLayout.PREFERRED_SIZE, 43, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(a2Text, javax.swing.GroupLayout.PREFERRED_SIZE, 97, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(87, 87, 87)
.addComponent(answer, javax.swing.GroupLayout.PREFERRED_SIZE, 67, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addGap(113, 113, 113)
.addComponent(jLabel1))
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jButton1)))
.addContainerGap(86, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(19, 19, 19)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(a1Text, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(a2Text, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addComponent(answer, javax.swing.GroupLayout.PREFERRED_SIZE, 24, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(60, 60, 60)
.addComponent(jLabel1)
.addGap(34, 34, 34)
.addComponent(jButton1)
.addContainerGap(140, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
int a;
a = Integer.parseInt(a1Text.getText()) + Integer.parseInt(a2Text.getText());
answer.setText("Answer" + a);
// TODO add your handling code here:
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Calculas().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JTextField a1Text;
private javax.swing.JTextField a2Text;
private javax.swing.JLabel answer;
private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel1;
// End of variables declaration
}
Test Class named Test.java
public class Test extends JFrame {
public static void main(String args[])
{
Calculas CAL = new Calculas();
CAL.Calculus();
}
}

Forgive me if this is naive, as Im not anything of a Java programmer...
But isnt it just because you need to set visible?
Calculas CAL = new Calculas();
CAL.setVisible(true);

The constructor of Calculas doesn't show (setVisible) the frame.
If you want to interact with the Calculas class in this manner, you should also be calling CAL.setVisible(true)
Also, by convention, all Java instance variables, should start with a lower case character and use camelCase conventions

In it's current form of your code, you can call the main method of your Calculas class in Test class or move the code to the Test class.
Warning: Extending JFrame is not a good Idea.
First alternative: You don't need to extend JFrame in Test
public class Test{
public static void main(String args[])
{
Calculas.main(new String[0]);
}
}
You haven't mentioned in your question how you want to be able to chose close or open, in console or in another JFrame or something...
Second Alternative:
But If I were you I could do something like this: wrap the code for look and feel in a separate method and call this from Test' s main.
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
/**
*
* #author user
*/
public class Calculas extends javax.swing.JFrame {
/**
* Creates new form Calculas
*/
public Calculas() {
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">
private void initComponents() {
a1Text = new javax.swing.JTextField();
a2Text = new javax.swing.JTextField();
jLabel1 = new javax.swing.JLabel();
jButton1 = new javax.swing.JButton();
answer = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jButton1.setText("jButton1");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(a1Text, javax.swing.GroupLayout.PREFERRED_SIZE, 43, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(a2Text, javax.swing.GroupLayout.PREFERRED_SIZE, 97, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(87, 87, 87)
.addComponent(answer, javax.swing.GroupLayout.PREFERRED_SIZE, 67, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addGap(113, 113, 113)
.addComponent(jLabel1))
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jButton1)))
.addContainerGap(86, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(19, 19, 19)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(a1Text, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(a2Text, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addComponent(answer, javax.swing.GroupLayout.PREFERRED_SIZE, 24, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(60, 60, 60)
.addComponent(jLabel1)
.addGap(34, 34, 34)
.addComponent(jButton1)
.addContainerGap(140, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
int a;
a = Integer.parseInt(a1Text.getText()) + Integer.parseInt(a2Text.getText());
answer.setText("Answer" + a);
// TODO add your handling code here:
}
public static setNimbusFeel(){
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Calculas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
}
// Variables declaration - do not modify
private javax.swing.JTextField a1Text;
private javax.swing.JTextField a2Text;
private javax.swing.JLabel answer;
private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel1;
// End of variables declaration
}
And test class like this:
public class Test{
public static void main(String args[])
{
Calculas cal=new Calculas();
//</editor-fold>
Calculas.setNimbusFeel();
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Calculas().setVisible(true);
}
});
}
}
Like this:

Here's an example of a basic structure you can use:
import java.awt.*;
import javax.swing.*;
class MyGui {
private JFrame window = new JFrame("This is the title");
public MyGui() {
initComponents();
window.setBounds(100, 50, 600, 400); //location, size
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setVisible(true);
}
public void initComponents() {
Container cp = window.getContentPane();
cp.setLayout(new FlowLayout() );
cp.add(new JLabel("Hello world") );
}
}
public class MyProg {
private static void createAndShowGUI() {
new MyGui();
}
public static void main(String[] args) {
//Schedule a job for the event dispatch thread:
//creating and showing this application's GUI.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
And in separate files:
MyGui.java
import java.awt.*;
import javax.swing.*;
public class MyGui {
private JFrame window = new JFrame("This is the title");
public MyGui() {
initComponents();
window.setBounds(100, 50, 600, 400); //location, size
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setVisible(true);
}
public void initComponents() {
Container cp = window.getContentPane();
cp.setLayout(new FlowLayout() );
cp.add(new JLabel("Hello world") );
}
}
MyProg.java
import javax.swing.*;
public class MyProg {
private static void createAndShowGUI() {
new MyGui();
}
public static void main(String[] args) {
//Schedule a job for the event dispatch thread:
//creating and showing this application's GUI.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}

Calculas CAL = new Calculas();
CAL.Calculus();
maybe, CAL.Calculas(); I dont know java but I realized that, sorry about my english:)