Question

In this task you will complete the calculation and implement the Clear button.

1. When an arithmetic operator is pressed retrieve the String from the JLabel, parse it to a Float value and assign it to a variable num1. Consult the Java API and the textbook to workout how to convert a String to a Float. Hint: use the same structure as when we convert a String to an Integer.

2. You should retrieve the operator and store it in a char variable op.

3. Follow the same procedure as before to input the second number. When the user presses the equals button retrieve the String from the label and assign the Float to a variable num2. Calculate the result and display it on the JLabel.

4. To complete the calculation define a private float method called calculate that accepts 3 parameters (char op, float num1, float num2). Use a switch statement to determine what operation to do and then return the result from the calculation.

5. Finally, if the user presses the Clear button then set num1 and num2 to 0 and set the text of the JLabel to 0.

import javax.swing.JFrame;
import javax.swing.*;
import java.awt.event.*;
/*
* Driver Class for the Calcultor
*
* @author
*/
public class CalculatorDriver {
public static void main(String[] args) {
// create JFrame object
JFrame frame=new JFrame("Simple Calculator");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// create object of CalculatorPanel class
CalculatorPanel panel=new CalculatorPanel();
frame.getContentPane().add(panel); // add panel into frame
frame.pack();
frame.setResizable(false); // frame should not be resizable
frame.setLocation(400,300); // set location of frame
frame.setVisible(true); // make frame visible
}
}

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

/**
* The calculator panel
* @author
*/
public class CalculatorPanel extends JPanel {
private static final long serialVersionUID = 1L;
private static final int CALC_WIDTH=250;
private static final int CALC_HEIGHT=225;

public CalculatorPanel() {
setLayout(new BorderLayout());
setBackground(Color.lightGray); // create the input/output panel
result = 0; // result variable of label
lastCommand = "=";
start = true;

// add the display
resultLabel = new JLabel("0", SwingConstants.RIGHT); // set the JLabel to RIGHT
resultLabel.setFont(new Font("Helvetica", Font.BOLD, 40)); // set the font size
add(resultLabel, BorderLayout.NORTH); // set the border layout to NORTH

// Action listener creates
ActionListener insert = new InsertAction();
ActionListener command = new CommandAction();

// CREATE A LAYOUT OF THE BUTTONS 4X4 grid
panel = new JPanel();
panel.setLayout(new GridLayout(4, 4)); //set the 4x4 grid
panel.setBackground(Color.DARK_GRAY); //set the background color

// add the button text and assign the action
addButton("7", insert);
addButton("8", insert);
addButton("9", insert);
addButton("/", command);
  
addButton("4", insert);
addButton("5", insert);
addButton("6", insert);
addButton("*", command);
  
addButton("1", insert);
addButton("2", insert);
addButton("3", insert);
addButton("-", command);

addButton("0", insert);
addButton(".", insert);
addButton("=", command);
addButton("+", command);
  
add(panel, BorderLayout.CENTER); // set the panel to center
}
  
// add button
private void addButton(String label, ActionListener listener) {
JButton button = new JButton(label);
button.setPreferredSize(new Dimension(55,30)); //set the button size
button.setFont(new Font("Helvetica", Font.BOLD, 15)); // set the font size
button.setForeground(Color.BLUE); //set the font color to blue
button.addActionListener(listener); // add the action listener
panel.add(button); // add the button to the panel
}

  
private class InsertAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String input = event.getActionCommand();
if (start) {
resultLabel.setText("");
start = false;
}
resultLabel.setText(resultLabel.getText() + input); //display the text to the label
}
}

private class CommandAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String command = event.getActionCommand();

if (start) {
if (command.equals("-")) {
resultLabel.setText(command);
start = false;
} else
lastCommand = command;
} else {
calculate(Double.parseDouble(resultLabel.getText()));
lastCommand = command;
start = true;
}
}
}

// method that calculate the result of two inputs
public void calculate(double x) {
if (lastCommand.equals("+"))
result += x; // add
else if (lastCommand.equals("-"))
result -= x; // subtract
else if (lastCommand.equals("*"))
result *= x; // multiply
else if (lastCommand.equals("/"))
result /= x; // divide
else if (lastCommand.equals("="))
result = x; // equals
resultLabel.setText("" + result); // display the result to the label
}

//variables
private JLabel resultLabel;
private JPanel panel;
private double result;
private String lastCommand;
private boolean start;
}

  
  
/**
* Define the calculate method
* Perform the calculations on <i>num1</i> and <i>num2</i> depending on
* the operation <i>op</i>
* @param op the operation
* @param num1 the first number of the calculation
* @param num2 the second number of the calculation
* @return the result of the calculation
*/

Hello, I need a help for this section... Could you please resolve it? I need a code. It's java.

Thanks a lot!

Answer 1

/* CalculatorPanel.java */

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

/**
* The calculator panel
* @author
*/
public class CalculatorPanel extends JPanel {
private static final long serialVersionUID = 1L;
private static final int CALC_WIDTH=250;
private static final int CALC_HEIGHT=325;

public CalculatorPanel() {
setLayout(new BorderLayout());
setBackground(Color.lightGray); // create the input/output panel
result = 0; // result variable of label
lastCommand = "=";
start = true;

// add the display
resultLabel = new JLabel("0", SwingConstants.RIGHT); // set the JLabel to RIGHT
resultLabel.setFont(new Font("Helvetica", Font.BOLD, 40)); // set the font size
add(resultLabel, BorderLayout.NORTH); // set the border layout to NORTH
// Action listener creates
ActionListener insert = new InsertAction();
ActionListener command = new CommandAction();

// CREATE A LAYOUT OF THE BUTTONS 4X4 grid
panel = new JPanel();
panel.setLayout(new GridLayout(4, 4)); //set the 4x4 grid
panel.setBackground(Color.DARK_GRAY); //set the background color

// add the button text and assign the action
addButton("7", insert);
addButton("8", insert);
addButton("9", insert);
addButton("/", command);
  
addButton("4", insert);
addButton("5", insert);
addButton("6", insert);
addButton("*", command);
  
addButton("1", insert);
addButton("2", insert);
addButton("3", insert);
addButton("-", command);

addButton("0", insert);
addButton(".", insert);
addButton("=", command);
addButton("+", command);
JButton clear = new JButton("Clear");
clear.setFont(new Font("Helvetica", Font.BOLD, 15)); // set the font size
clear.setForeground(Color.BLUE); //set the font color to blue
clear.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
resultLabel.setText("0");
}
});
add(clear,BorderLayout.SOUTH);
add(panel, BorderLayout.CENTER); // set the panel to center
}
// add button
private void addButton(String label, ActionListener listener) {
JButton button = new JButton(label);
button.setPreferredSize(new Dimension(55,30)); //set the button size
button.setFont(new Font("Helvetica", Font.BOLD, 15)); // set the font size
button.setForeground(Color.BLUE); //set the font color to blue
button.addActionListener(listener); // add the action listener
panel.add(button); // add the button to the panel
}

  
private class InsertAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String input = event.getActionCommand();
if (start) {
resultLabel.setText("");
start = false;
}   
  
if(!resultLabel.getText().equals("0"))
resultLabel.setText(resultLabel.getText() + input); //display the text to the label when no 0
else{
resultLabel.setText( input); //display the text to the label when 0
}
}
}

private class CommandAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String command = event.getActionCommand();

if (start) {

if (command.equals("-")) {
resultLabel.setText(command);
start = false;
} else
lastCommand = command;
} else {
calculate(Double.parseDouble(resultLabel.getText()));
lastCommand = command;
start = true;
}
}
}

// method that calculate the result of two inputs
public void calculate(double x) {
if (lastCommand.equals("+"))
result += x; // add
else if (lastCommand.equals("-"))
result -= x; // subtract
else if (lastCommand.equals("*"))
result *= x; // multiply
else if (lastCommand.equals("/"))
result /= x; // divide
else if (lastCommand.equals("="))
result = x; // equals
resultLabel.setText("" + result); // display the result to the label
}

//variables
private JLabel resultLabel;
private JPanel panel;
private double result;
private String lastCommand;
private boolean start;

}

/* CalculatorDriver.java*/

import javax.swing.JFrame;
import javax.swing.*;
import java.awt.event.*;
/*
* Driver Class for the Calcultor
*
* @author
*/
public class CalculatorDriver {
public static void main(String[] args) {
// create JFrame object
JFrame frame=new JFrame("Simple Calculator");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// create object of CalculatorPanel class
CalculatorPanel panel=new CalculatorPanel();
frame.getContentPane().add(panel); // add panel into frame
frame.pack();
frame.setResizable(false); // frame should not be resizable
frame.setLocation(400,300); // set location of frame
frame.setVisible(true); // make frame visible
}
}

/* OUTPUT */

/* PLEASE UPVOTE */