Question

Objective:

Write a Java program that will use a JComboBox from which the user will select to convert a temperature from either Celsius to Fahrenheit, or Fahrenheit to Celsius. The user will enter a temperature in a text field from which the conversion calculation will be made. The converted temperature will be displayed in an uneditable text field with an appropriate label.

Specifications

• Structure your file name and class name on the following pattern:
  • The first three letters of your last name (begin with upper case.).
    • Then the first two letters of your first name (begin with upper case.).
    • Follow this with the name of the program: guiTempConv.
    • For a student called ’John Doe,’ the class name and file name would be: DoeJoGuiTempConv

The program structure and format will be the one used in the videos and supporting material for this chapter.

• Make sure you have the following comments at the beginning of your program:

/*
 * Program Name:   The program name.
 * Author:         Your first and last name.
 * Date Written:   The current date.
 * The class name: CIT 149 Java 1
 * Description:    Meaningful description of the purpose of the program.
 */

• Use good comments.
• Think about the problem and decide what type each of the input numbers should be. Also, think about the calculations and decide what type the variables should be that will hold the results of the calculations.
• Use camel casing for variable names, and use descriptive variable names. Do not use general variable names like "tax" or "total."
• Create a JComboBox with two options: Celsius to Fahrenheit and Fahrenheit to Celsius.
• Use a text field to accept a double that represents the amount of the temperature.
  • Test the user input number to ensure that it is a double.
• Create two methods for the temperature conversions:
  • Use degreesC = 5(degreesF - 32)/9; for the conversion from Celsius to Fahrenheit.
  • Use degreesF = (9(degreesC)/5) + 32; for the conversion from Fahrenheit to Celsius.
• Use an un-editable text field to show the converted temperature.
• Display a label that describes the converted temperature type.
• Have the cursor come back to the temperature entry field.
• See the GUI format below.

Use parseDouble to convert the input to a double for use in the calculation.

use an inner class for the listener.

Creating the Un-editable Text Field

• An unedtable field is a field that may contain data, but you are not able to edit it. It is basically used to display answers or results of calculations.
• The field itself is a standard text field.
  -- myTextField = new JTextField(10);
• The line below makes that field un-editable.
  • myTextField.setEditable(false);
• You then, of course, have to add it to the panel.
  • panel.add(text2);

Creating the JComboBox

• In this program you will need to create a JComboBox. You have seen these many times in programs that you have used. They are just one of the many GUI components available in Java.
• You will create the JComboBox as you have other components that you have already used. The JComboBox, due to its nature, has some specifications to set.
• Here are the steps to set up the JComboBox:
  • Set a variable for the JComboBox:
    • private JComboBox tempConvert; // Define the JComboBox in the public class.
  • Create a String array of choices for the JComboBox:
    -- String[] convChoices = {"C to F","F to C"}; // Declare an array to hold the choices (in this case only two).
  • Create the JComboBox object:
    • conversionSelector = new JComboBox(convChoices); // Passing the array
    • Add a listener
    • conversionSelector.addActionListener(listen);
  • Then add it to the panel:
    • panel.add(conversionSelector);
  • Later in your logic you will check the selected item:
    • if (conversionSelector.getSelectedItem().toString() == ("C to F"))
    • The "C to F" and "F to C" are simply strings, so you can use whatever labels you want for items in the combo box.

Answer 1

Java program to implement the above functionality is :

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class GuiTempConv {
        
        static JFrame f; 
    static JLabel label; 
    static JComboBox conversionSelector;        
    static JTextField result,input;

        public static void main(String[] args) 
    { 
        f = new JFrame("frame"); 
        String[] s = {"C to F","F to C"};
        GuiTempConv g = new GuiTempConv();
        ConvertTemperature c = g.new ConvertTemperature();
        
        conversionSelector = new JComboBox(s); 
        conversionSelector.addActionListener(c);
        
        input  = new JTextField(8);        
        result = new JTextField(8);
        
        result.setText("");      
        result.setEditable(false);
        
        label = new JLabel("F");        
        
        
        JPanel p = new JPanel();       
        p.add(input);
        p.add(label);
        p.add(conversionSelector);        
        p.add(result);
        p.add(label);
        f.add(p); 
        f.setSize(400, 400);        
        f.show();
    }   
        
        public static double fahrenheittoCelsius(double temp){
                return 5 * (temp - 32)/9;
                
        }
        
        public static double  celsiustoFahrenheit(double temp){
                return (9 * (temp)/5) + 32;
                
        }
        
         private class ConvertTemperature implements ActionListener {           
                        @Override
                        public void actionPerformed(ActionEvent e) {
                          if(input.getText() != null){  
                                double temp = Double.parseDouble(input.getText());
                    double res=0;
                                if(conversionSelector.getSelectedItem().toString()=="C to F"){
                                         res=celsiustoFahrenheit(temp);
                                         label.setText("F");
                                }else{
                                    res=fahrenheittoCelsius(temp);
                                    label.setText("C");
                                }
                                result.setText(res+"");
                          }     
                        }          
                }
         
}

The output screenshots are as below:

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