Question

Java

Please comment code

Create an Interactive JavaFX Application

• Create an application with the following controls:
  • A Label control with the following text displayed: "First Number:"
  • A Label control with the following text displayed: "Second Number:"
  • An empty TextField control beside the First Number label.
  • An empty TextField control beside the Second Number label.
  • Five buttons:
    • Button 1 labeled +
    • Button 2 labeled -
    • Button 3 labeled *
    • Button 4 labeled /
    • Button 5 labeled =
  • An empty Label control that will display the result of a mathematical operation.
• Make sure there is spacing between each control.
• Align the controls:
  • The Label control with the text First Number on the first line with a TextField beside it.
  • The buttons labeled +, -, *, / on the second line. Make sure there is space between the buttons.
  • The Label control with the text Second Number on the third line with a TextField beside it.
  • The button labeled = on the fourth line.
  • The label that will contain the result of the operation on the fifth line.
  • Make sure the window is large enough to display all controls.
• Create an event for each button:
  • Capture the text entered in the first TextField control. Note that values in a TextField are strings. You will need to convert it to a numeric value.
  • Capture the text entered in the second TextField control. Note that values in a TextField are strings. You will need to convert it to a numeric value.
  • Perform the mathematical operation indicated by the button being pressed.
  • When the = button is pressed display the result of the calculation in the results label.
• The order of execution for the user is as follows. Your program must respond in this order:
  • Enter a value in the first TextField.
  • Click on an operation button.
  • Enter a value in the second TextField.
  • Click on the equals button.
  • View the result in the Label control.
• Display the window.

Answer 1

Program screenshot:

Sample output screenshot:

Code to copy:

/**************** File name: Calculator.java *****************/
package application;

// Import statements
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.stage.Stage;

import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;

// Create a class calculator
public class Calculator extends Application
{
   // Required components
   Label lblFNum;
   TextField txtFNum;

   Button btnPlus;
   Button btnMinus;
   Button btnMul;
   Button btnDiv;

   Label lblSNum;
   TextField txtSNum;

   Button btnEql;

   Label lblResult;

   double num1 = 0;
   double num2 = 0;
   char operation = '=';

   @Override
   public void start(Stage primaryStage) throws Exception
   {

       lblFNum = new Label("First Number:");
       txtFNum = new TextField("");

       btnPlus = new Button("+");
       btnMinus = new Button("-");
       btnMul = new Button("*");
       btnDiv = new Button("/");
       btnEql = new Button("=");

       lblSNum = new Label("Second Number:");
       txtSNum = new TextField("");

       lblResult = new Label("Result");

       // Create a panel
       GridPane root = new GridPane();
      
       // Align the position center
       root.setAlignment(Pos.CENTER);

       root.setHgap(10);
       root.setVgap(10);

       // (columnNumberStart, Row Number, ColumnsToMerge, NumComponents)
       // Add the components to the panel and sets
       // the position of the components in the panel
       root.add(lblFNum, 0, 0, 2, 1);
       root.add(txtFNum, 2, 0, 2, 1);

       root.add(btnPlus, 0, 1);
       root.add(btnMinus, 1, 1);
       root.add(btnMul, 2, 1);
       root.add(btnDiv, 3, 1);

       root.add(lblSNum, 0, 3, 2, 1);
       root.add(txtSNum, 2, 3, 2, 1);

       root.add(btnEql, 0, 4, 4, 1);

       lblResult.setAlignment(Pos.CENTER);

       root.add(lblResult, 0, 5, 4, 1);

       setWidths();

       // Add the panel to the screen
       Scene scene = new Scene(root, 300, 250);
      
       // Set title
       primaryStage.setTitle("Calculator");
      
       // Add screen to the stage
       primaryStage.setScene(scene);
      
       // Display stage
       primaryStage.show();

       // Create the button events
       btnPlus.setOnAction(new EventHandler<ActionEvent>()
       {
           @Override
           public void handle(ActionEvent e)
           {
               operation = '+';
           }
       });

       btnMinus.setOnAction(new EventHandler<ActionEvent>()
       {
           @Override
           public void handle(ActionEvent e)
           {
               operation = '-';
           }
       });
       btnMul.setOnAction(new EventHandler<ActionEvent>()
       {
           @Override
           public void handle(ActionEvent e)
           {
               operation = '*';
           }
       });
       btnDiv.setOnAction(new EventHandler<ActionEvent>()
       {
           @Override
           public void handle(ActionEvent e)
           {
               operation = '/';
           }
       });

       // This button event is helps to perform the math calcuation.
       btnEql.setOnAction(new EventHandler<ActionEvent>()
       {
           @Override
           public void handle(ActionEvent e)
           {
               num1 = Double.parseDouble(txtFNum.getText());
               num2 = Double.parseDouble(txtSNum.getText());

               double result = 0.0;
               switch (operation)
               {
               case '+':
                   result = num1 + num2;
                   break;

               case '-':
                   result = num1 - num2;
                   break;

               case '*':
                   result = num1 * num2;
                   break;

               case '/':
                   if (num2 == 0)
                   {
                       lblResult.setText("Inf");
                       break;
                   }
                   else
                   {
                       result = num1 / num2;
                       break;
                   }

               default:
                   lblResult.setText("Please select the math operator.");
                   break;
               }

               if(num2 != 0 || operation != '/')
               {
                   lblResult.setText(String.valueOf(result));  
               }
              
           }
       });

   }

   // Create a method named setWidths.
   // This method helps to set the size of the each component
   private void setWidths()
   {
       lblFNum.setPrefWidth(100);
       txtFNum.setPrefWidth(50);

       btnPlus.setPrefWidth(38);
       btnMinus.setPrefWidth(38);
       btnMul.setPrefWidth(38);
       btnDiv.setPrefWidth(38);

       lblSNum.setPrefWidth(100);
       txtSNum.setPrefWidth(50);

       btnEql.setPrefWidth(200);

       lblResult.setPrefWidth(200);

   }

   // Create a main method to run the program.
   public static void main(String args[])
   {
       // Launch the application
       launch(args);
   }

}