Problem

Write a Java program Temp, that converts celsius to fahrenheit or vice versa.

Your program should do the following:

• prompt the user for a 1-character string c (celsius) or f (fahrenheit) that tells the program which unit you are entering
• prompt the user for the temperature
• output the solution followed by a 'c' or 'f' to denote the final units

This program will cover the following topics:

• working with primitive data types
• integer arithmetic
• using the Math class
• working with real numbers: the double data type
• casting

Example: User inputs "c" and "10" would result in "50f"

Use the following formula to convert your units:

<math>F = 9C/5 + 32</math>

Temperature Calculator

Solution

Start by importing the swing java package.

 import javax.swing.*; 

Define your variables, we will need doubles in case of decimal results, and a string value for the unit

 double temperature, result;
String unit; 

Next start by capturing the user input using JOptionPane. We will need to use Integer.parseInt to cast the String result to an integer for the temperature.

 unit = JOptionPane.showInputDialog("Enter the 1-character temperature you want to convert from c (Celsius) or f (Fahrenheit)") ;
temperature = Integer.parseInt(JOptionPane.showInputDialog("Enter the current temperature in the units you specified")); 

Now we need to use conditional statements to check for each unit, one for Celsius and one for Fahrenheit. One thing to note is that because unit is a String data type, we will have to only extract the first character assuming it has be entered in correctly, this is easily accomplished using where index is the position at which the char character is at in the String.

Note: this is one approach to it, there are many others. This also assumes that users enter valid input, invalid input will result in an error. An alternate solution could be to use string comparisons like .equals() which is defined in your course material.

 unit.charAt(int index) 

For each case, calculate your results and print the output using System.out. We rounded our answer to make use of the built in Math class. To round it to two decimal places or the nearest one-hundredth you have to multiply by 100 since Math.round returns an int and then divide by 100.0.

Note: divide by 100.0 in order to keep the result a double, otherwise it will result in an integer.

 if (unit.charAt(0) == 'c')
{
	result = 9 * temperature / 5 + 32;
	result = Math.round(result*100)/100.0;
	System.out.println(temperature + " degree Celsius = " + result + " degree Fahrenheit");
}
else if (unit.charAt(0) == 'f')
{
	result = (temperature - 32) * 5 / 9;
	result = Math.round(result*100)/100.0;
	System.out.println(temperature + " degree Fahrenheit = " + result + " degree Celsius");
} 

To make your program more robust, you may want to use an else case for all invalid characters.

 else
	System.out.println("You entered an incorrect unit, please try again"); 

Code

Solution Code

import javax.swing.*;

public class  Temp
{

	public static void main(String[] args)
	{
		double temperature, result;
		String unit;
		unit = JOptionPane.showInputDialog("Enter the 1-character temperature you want to convert from c (Celsius) or f (Fahrenheit)") ;
		temperature = Integer.parseInt(JOptionPane.showInputDialog("Enter the current temperature in the units you speficied"));

		if (unit.charAt(0) == 'c')
		{
			result = 9 * temperature / 5 + 32;
			result = Math.round(result*100)/100.0;
			System.out.println(temperature + " degree Celsius = " + result + " degree Fahrenheit");
		}
		else if (unit.charAt(0) == 'f')
		{
			result = (temperature - 32) * 5 / 9;
			result = Math.round(result*100)/100.0;
			System.out.println(temperature + " degree Fahrenheit = " + result + " degree Celsius");
		}
		else
			System.out.println("You entered an incorrect unit, please try again");

	}
}