Simple GUI Calculator in Java

Hello world! I'm back. It’s been four years since my last post. I’d been very busy with work in these past few years that I haven’t had time to blog. I missed blogging somehow and this year I figure I’ll get back to blogging again.

We are going to be making simple programming projects starting from now and for our first project, let’s make a simplest calculator using Java. In this project we’ll be using BlueJ as our Java Development Tool.

1. Download BlueJ installer from https://www.bluej.org/ then install it.

2. Click Start>Click BlueJ.

3. Click Project>New Project>For the sake of example, let’s use Java as a project name.



4. Click New Class>Select Class in the class type radio buttons then enter Calc in the Class Name textbox.



5. Double-click the Calc object.



6. A Window containing default BlueJ source code will then appear. Press Ctrl + A to select all the codes, then Press Delete.



7. Enter the following code:

view plainprint?
  1. //imports the necessary packages.  
  2. //swing for frame, awt for controls, and event for button events  
  3. import javax.swing.*;  
  4. import java.awt.*;  
  5. import java.awt.event.*;  
  6. //creates a class named Calc and prepares it to accept an event  
  7. public class Calc extends JFrame implements ActionListener  
  8. {  
  9. //creates our controls  
  10.   JTextField ansTextField=new JTextField("",18);  
  11.   JButton oneButton=new JButton("1");  
  12.   JButton twoButton=new JButton("2");  
  13.   JButton plusButton=new JButton("+");  
  14.   JButton minusButton=new JButton("-");  
  15.   JButton equalsButton=new JButton("=");  
  16.  //declares three variables  
  17.   int intNum1,intNum2;  
  18.   String strOperator;  
  19.     public Calc()  
  20. {  
  21.    //creates two panels  
  22.    JPanel topPanel=new JPanel();  
  23.    JPanel bottomPanel=new JPanel();  
  24.    //create two layouts  
  25.    BorderLayout border=new BorderLayout(5,5);  
  26.    FlowLayout flow=new FlowLayout(FlowLayout.RIGHT,10,10);  
  27.    //apply the borderLayout to frame  
  28.    setLayout(border);  
  29.    //prepare our buttons to accept an event  
  30.    oneButton.addActionListener(this);  
  31.    twoButton.addActionListener(this);  
  32.    plusButton.addActionListener(this);  
  33.    minusButton.addActionListener(this);  
  34.    equalsButton.addActionListener(this);  
  35.    //adds the textbox to the top panel  
  36.    topPanel.add(ansTextField);  
  37.    //applies flow layout to bottom panel  
  38.    bottomPanel.setLayout(flow);  
  39.    //add the buttons to the bottom panel  
  40.    bottomPanel.add(oneButton);  
  41.    bottomPanel.add(twoButton);  
  42.    bottomPanel.add(plusButton);  
  43.    bottomPanel.add(minusButton);  
  44.    bottomPanel.add(equalsButton);  
  45.    add(topPanel,BorderLayout.NORTH);  
  46.    add(bottomPanel);  
  47.    //setup our frame  
  48.    setSize(200,200);  
  49.    setLocation(0,0);  
  50.    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  
  51.    setTitle("Calculator");  
  52.    setVisible(true);  
  53.    
  54. }  
  55. public void actionPerformed(ActionEvent e)  
  56. {  
  57.     //getSource determines the name of the control that recieves an event  
  58.     Object source=e.getSource();  
  59.     //if the name of the control that recieves an event is oneButton, display 1 in the textfield  
  60.     if(source==oneButton)  
  61.     {  
  62.         ansTextField.setText(ansTextField.getText() + oneButton.getText());  
  63.     }  
  64.     //if the name of the control is twoButton, display 2 in the textfield  
  65.     //you can add else ifs for numbers 3 to 9. I just leave that to you to figure out  
  66.     else if(source==twoButton)  
  67.     {  
  68.          ansTextField.setText(ansTextField.getText() + twoButton.getText());  
  69.        
  70.     }  
  71.     //if it is plusButton, get the value displayed in the textfield and place it  
  72.     //in a variable named intNum1  
  73.     //Store "+" in the strOperator variable then clear the text field  
  74.     else if(source==plusButton)  
  75.     {  
  76.         intNum1=Integer.parseInt(ansTextField.getText());  
  77.         strOperator="+";  
  78.         ansTextField.setText("");  
  79.           
  80.     }  
  81.    //if it is minusButton, get the value displayed in the textfield and place it  
  82.    //in a variable named intNum1  
  83.    //store "-" in the strOperator variable then clear the text field  
  84.    else if(source==minusButton)  
  85.     {  
  86.         intNum1=Integer.parseInt(ansTextField.getText());  
  87.         strOperator="-";  
  88.         ansTextField.setText("");  
  89.           
  90.     }  
  91.     //if the name of the control that recieves an event is equals button  
  92.     //get the current value of the text field and assign it as a value of intNum2  
  93.     //if the current value of strOperator is + add the two numbers, if it's value is -  
  94.     //subtract the two numbers  
  95.     else if(source==equalsButton)  
  96.     {  
  97.         intNum2=Integer.parseInt(ansTextField.getText());  
  98.         if(strOperator=="+")  
  99.         {  
  100.           ansTextField.setText(Integer.toString(intNum1 + intNum2));   
  101.         }  
  102.           if(strOperator=="-")  
  103.         {  
  104.           ansTextField.setText(Integer.toString(intNum1 - intNum2));   
  105.         }  
  106.           
  107.     }  
  108. }  
  109. //Creates an instance of our class so that we can run it  
  110. public static void main(String[] args)  
  111. {  
  112.   Calc c=new Calc();    
  113. }  
  114. }  


8. Click the compile button.

9. Close the code window.

10. Right-click the class object>Select void main(String[] args) to run your application.



11. You should then see the following output:



You can use this and make a complete basic calculator. Of course I leave that to you to figure out. If you are having a hard time, you can download the source code here Good luck!
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Enabling Broadband Internet Connection on Kali Linux

Hey there. Am sure you probably know that Kali Linux is a very powerful pen testing and computer forensics tool available for free download at http://www.kali.org/. But you might not know how to enable broadband Internet connections in it. Trust me, I had the same problems before as well. I’ve search the net to no avail so I decided to do something about it. Anyways, here’s how:
1. Insert your broadband stick on your USB port. In this case I’m using Smart Bro so its icon should then appear on the Kali Linux desktop.

2.In the top right side area of the kali desktop, Right-click the networking icon then select Edit Connections.

3. The Network Connections window should then appear.Select the mobile broadband tab then click Add.

4.On the next window select you provider’s country or region. In this case since iv’e selected Philippines[since Smart Bro is in the Philippines...depends on your service provider’s location]>Continue.

5. 5. Select your Mobile Broadband Provider. In this case ive’d selected Smart [since Smart Bro’s provider is Smart...again the value in here depends on your provider]>Continue.

6.Select your data provider plan. In this case I’ve accepted the default settings>Continue.

7. Click the Apply button to confirm your settings.
8. A connection name window should then appear. In this case, ived entered “Smart Bro” as a connection name. Any name should do. Just wanted it to be descriptive>Apply.

9. To enable your broadband internet connection, CLICK(not right-click) the networking icon near in the notifications area>Then select your broadband connection name. In this case Iv’e selected Smart Bro.

The network icon should now change into a broadband signal meter icon and you should not be able to connect to internet using a broadband connection.

Enjoy xD
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