27.5.4: Java Examples
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Temperature
The temperature program main function is listed twice, once using if-then-else and once using switch, followed by the supporting functions.
If Then Else
// This program asks the user to select Fahrenheit or Celsius conversion // and input a given temperature. Then the program converts the given // temperature and displays the result. // // References: // https://www.mathsisfun.com/temperature-conversion.html // https://en.wikibooks.org/wiki/Java_Programming import java.util.*; public class Main { private static Scanner input = new Scanner(System.in); public static void main(String[] args) { String choice; choice = getChoice(); if (choice.equals("C") || choice.equals("c")) { processCelsius(); } else if (choice.equals("F") || choice.equals("f")) { processFahrenheit(); } else { System.out.println("You must enter C to convert to Celsius or F to convert to Fahrenheit."); } }
Switch
public static void main(String[] args) { String choice; choice = getChoice(); switch (choice) { case "C": case "c": processCelsius(); break; case "F": case "f": processFahrenheit(); break; default: System.out.println("You must enter C to convert to Celsius or F to convert to Fahrenheit."); } }
Supporting Functions
public static String getChoice() { String choice; System.out.println("Enter C to convert to Celsius or F to convert to Fahrenheit:"); choice = input.nextLine(); return choice; } public static void processCelsius() { double temperature; double result; temperature = getTemperature("Fahrenheit"); result = calculateCelsius(temperature); displayResult(temperature, "Fahrenheit", result, "Celsius"); } public static void processFahrenheit() { double temperature; double result; temperature = getTemperature("Celsius"); result = calculateFahrenheit(temperature); displayResult(temperature, "Celsius", result, "Fahrenheit"); } public static double getTemperature(String scale) { double temperature; System.out.println("Enter " + scale + " temperature:"); temperature = input.nextDouble(); return temperature; } public static double calculateCelsius(double fahrenheit) { double celsius; celsius = (fahrenheit - 32) * 5 / 9; return celsius; } public static double calculateFahrenheit(double celsius) { double fahrenheit; fahrenheit = celsius * 9 / 5 + 32; return fahrenheit; } public static void displayResult(double temperature, String fromScale, double result, String toScale) { System.out.println(Double.toString(temperature) + "° " + fromScale + " is " + result + "° " + toScale); } }
Output
Enter C to convert to Celsius or F to convert to Fahrenheit: c Enter Fahrenheit temperature: 100 100.0° Fahrenheit is 37.77777777777778° Celsius Enter C to convert to Celsius or F to convert to Fahrenheit: f Enter Celsius temperature: 100 100.0° Celsius is 212.0° Fahrenheit Enter C to convert to Celsius or F to convert to Fahrenheit: x You must enter C to convert to Celsius or F to convert to Fahrenheit.
References
- Wikiversity: Computer Programming