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:
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!
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:
//imports the necessary packages. //swing for frame, awt for controls, and event for button events import javax.swing.*; import java.awt.*; import java.awt.event.*; //creates a class named Calc and prepares it to accept an event public class Calc extends JFrame implements ActionListener { //creates our controls JTextField ansTextField=new JTextField("",18); JButton oneButton=new JButton("1"); JButton twoButton=new JButton("2"); JButton plusButton=new JButton("+"); JButton minusButton=new JButton("-"); JButton equalsButton=new JButton("="); //declares three variables int intNum1,intNum2; String strOperator; public Calc() { //creates two panels JPanel topPanel=new JPanel(); JPanel bottomPanel=new JPanel(); //create two layouts BorderLayout border=new BorderLayout(5,5); FlowLayout flow=new FlowLayout(FlowLayout.RIGHT,10,10); //apply the borderLayout to frame setLayout(border); //prepare our buttons to accept an event oneButton.addActionListener(this); twoButton.addActionListener(this); plusButton.addActionListener(this); minusButton.addActionListener(this); equalsButton.addActionListener(this); //adds the textbox to the top panel topPanel.add(ansTextField); //applies flow layout to bottom panel bottomPanel.setLayout(flow); //add the buttons to the bottom panel bottomPanel.add(oneButton); bottomPanel.add(twoButton); bottomPanel.add(plusButton); bottomPanel.add(minusButton); bottomPanel.add(equalsButton); add(topPanel,BorderLayout.NORTH); add(bottomPanel); //setup our frame setSize(200,200); setLocation(0,0); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setTitle("Calculator"); setVisible(true); } public void actionPerformed(ActionEvent e) { //getSource determines the name of the control that recieves an event Object source=e.getSource(); //if the name of the control that recieves an event is oneButton, display 1 in the textfield if(source==oneButton) { ansTextField.setText(ansTextField.getText() + oneButton.getText()); } //if the name of the control is twoButton, display 2 in the textfield //you can add else ifs for numbers 3 to 9. I just leave that to you to figure out else if(source==twoButton) { ansTextField.setText(ansTextField.getText() + twoButton.getText()); } //if it is plusButton, get the value displayed in the textfield and place it //in a variable named intNum1 //Store "+" in the strOperator variable then clear the text field else if(source==plusButton) { intNum1=Integer.parseInt(ansTextField.getText()); strOperator="+"; ansTextField.setText(""); } //if it is minusButton, get the value displayed in the textfield and place it //in a variable named intNum1 //store "-" in the strOperator variable then clear the text field else if(source==minusButton) { intNum1=Integer.parseInt(ansTextField.getText()); strOperator="-"; ansTextField.setText(""); } //if the name of the control that recieves an event is equals button //get the current value of the text field and assign it as a value of intNum2 //if the current value of strOperator is + add the two numbers, if it's value is - //subtract the two numbers else if(source==equalsButton) { intNum2=Integer.parseInt(ansTextField.getText()); if(strOperator=="+") { ansTextField.setText(Integer.toString(intNum1 + intNum2)); } if(strOperator=="-") { ansTextField.setText(Integer.toString(intNum1 - intNum2)); } } } //Creates an instance of our class so that we can run it public static void main(String[] args) { Calc c=new Calc(); } }
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!