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Java program to Convert Fahrenheit to Celsius

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Overview

In this tutorial, we will develop a java program to convert Fahrenheit to Celsius temperature. The mathematical formula to converting Fahrenheit temperature to Celsius temperature is below:

 

Celsius = 5 * (Fahrenheit – 32) /9

 

IPO chart

Input Process Output
Temperature in Fahrenheit Celsius = 5.0 * (fahrenheit – 32.0) / 9.0; Temperature in Celsius

Example

Let’s calculate and evaluate one example calculation.

C = (5/9)*(F – 32)

where:
F is the Fahrenheit Temperature
C is the Celsius Temperature.

Input

Let F = 77 degrees Fahrenheit

Let’s calculate the equivalent Celsius temperature.

The input is 77.

C = (5/9)*(77 – 32)

C = (5/9)*(45)

C = 25

Output

The equivalent Celsius temperature is 25 degrees.

Eclipse IDE Setup

Some steps and instructions to create a Java application on Eclipse IDE:

https://www.testingdocs.com/create-a-new-java-project-in-eclipse/

https://www.testingdocs.com/create-java-package-in-eclipse-ide/

https://www.testingdocs.com/create-a-new-java-class-in-a-project/

https://www.testingdocs.com/run-java-project-in-eclipse/

Java Program

The following program takes the input of Fahrenheit temperature from the user. It calculates the Celsius equivalent of the Fahrenheit temperature. Displays the Celsius temperature in the output.

 

public class FahrenheitToCelsius {

    public static void main(String args[]) throws IOException {
        BufferedReader input = null;
        double fahrenheit,celsius;
        try {
            input = new BufferedReader(new InputStreamReader(System.in));
            System.out.print("Please enter temperature in Fahrenheit : ");
            fahrenheit = Double.parseDouble(input.readLine());

            celsius = 5.0 * (fahrenheit - 32.0) / 9.0;
            System.out.println("The temperature in Fahrenheit provided:" 
+ fahrenheit + " F");
            System.out.println("The temperature in Celsius is:" 
+ celsius + " C");
        }
        catch(IOException ioe)
        {
            System.out.print("Unexpected IO error.");
        }
        catch(NumberFormatException nfe)
        {
            System.out.print("Please check for valid input.");
        }
        catch(Exception e)
        {
            System.out.print("Unexpected error.");
        }
        finally
        {
          if (input != null) {
          input.close();
           }
} } }

Sample Output

Now run the program with sample input let’s say 32F. Calculate the output according the formula by hand.

Celsius = 5 * (Fahrenheit – 32) /9

= 5 * ( 32- 32) / 9

= 5 * 0

=0 C

Test Cases

Let’s test the program with sample test cases to check if the program is working as intended.

 

Test Case Scenario Detailed Steps Test Data Expected Result Actual Result
Happy path. Temperature in Integers Run the Java program.
Enter Fahrenheit temperature		 32 0
Temperature in Real Run the Java program.
Enter Fahrenheit temperature		 98.4 36.89
Negative Test Case Run the Java program.
Enter Fahrenheit temperature		 Invalid data : dsafg Program Error Message

Test Case: Enter Real numbers

Please enter temperature in Fahrenheit : 98.4
The temperature in Fahrenheit provided:98.4 F
The temperature in Celsius is:36.888888888888886 C

To round the output:

https://www.testingdocs.com/questions/how-to-round-a-double-value-in-java/

 

Exercise

Now that you know to convert Fahrenheit temperature to Celsius. Write a similar program to convert Celsius to Fahrenheit temperature. Your program should take input the Celsius temperature value and convert the temperature into Fahrenheit and display the output.

More information on Java can be found on the official website:

https://www.oracle.com/in/java/

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