loops.java

/** 
 * This program converts a Fahrenheit temperature to Celsius.
 * 
 * Input:
 * Fahrenheit temperature
 * 
 * Output:
 * Fahrenheit temperature
 * Celsius temperature
 * 
 * Example:
 * Enter Fahrenheit temperature or press <Enter> to quit:
 * 100
 * 100.0° Fahrenheit is 37.8° Celsius
 * 
 * Enter Fahrenheit temperature or press <Enter> to quit:
 * ...
 * 
 * References:
 * * http://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html
 * * https://www.w3resource.com/slides/java-coding-style-guide.php
 * * https://en.wikipedia.org/wiki/Javadoc
 * * http://www.mathsisfun.com/temperature-conversion.html
 */

importjava.util.Scanner;

/**
 * Runs main program logic.
 */
class Main{
publicstaticfinaldoubleABSOLUTE_ZERO=-459.67;
publicstaticfinalintTEMPERATURE_DIFFERENCE=32;
publicstaticfinaldoubleTEMPERATURE_RATIO=5.0/9;

publicstaticvoidmain(String[]args){
while(true){
try{
doublefahrenheit=getFahrenheit();
doublecelsius=fahrenheitToCelsius(fahrenheit);
displayResults(fahrenheit,celsius);
displayTable(fahrenheit);
}
catch(Exceptionexception){
System.out.println("Unexpected error.");
exception.printStackTrace();
System.exit(1);
}
}
}

/**
 * Gets Fahrenheit temperature.
 * 
 * @return Fahrenheit temperature
 * 
 * Exits:
 * If no temperature is entered.
 */
privatestaticdoublegetFahrenheit(){
while(true){
try{
System.out.println("Enter Fahrenheit temperature or press <Enter> to quit:");
Scannerscanner=newScanner(System.in);
Stringtext=scanner.nextLine();

if(text.isEmpty()){
System.exit(0);
}

doublefahrenheit=Double.parseDouble(text);
if(fahrenheit<ABSOLUTE_ZERO){
System.out.println("Fahrenheit temperature cannot be below absolute zero.");
System.out.println("Temperature is invalid.\n");
}
returnfahrenheit;
}
catch(NumberFormatExceptionexception){
System.out.println("Fahrenheit temperature must be a floating point value.");
System.out.println("NumberFormatException: Temperature is invalid.\n");
}
}
}

/**
 * Converts Fahrenheit temperature to Celsius.
 * 
 * @param Fahrenheit temperature
 * @return Celsius temperature
 * @throws IllegalArgumentException if temperature is below absolute zero
 */
privatestaticdoublefahrenheitToCelsius(doublefahrenheit){
if(fahrenheit<ABSOLUTE_ZERO){
thrownewIllegalArgumentException(
"fahrenheit must not be below absolute zero.");
}
doublecelsius;
celsius=(fahrenheit-TEMPERATURE_DIFFERENCE)*TEMPERATURE_RATIO;
returncelsius;
}

/**
 * Displays Fahrenheit and Celsius temperatures.
 * 
 * @param Fahrenheit temperature
 * @param Celsius temperature
 * @throws AssertionError if fahrenheit is less than absolute zero
 * @throws AssertionError if celsius is less than absolute zero
 */
privatestaticvoiddisplayResults(doublefahrenheit,doublecelsius){
assertfahrenheit>=ABSOLUTE_ZERO:"fahrenheit less than absolute zero";
assertcelsius>=fahrenheitToCelsius(ABSOLUTE_ZERO):
"celsius less than absolute zero";
System.out.println(String.format(
"%1$.1f° Fahrenheit is %2$.1f° Celsius\n",
fahrenheit,
celsius));
}

/**
 * Displays nearest multiples of 10 Fahrenheit and Celsius temperatures.
 * 
 * @param Fahrenheit temperature
 * @throws AssertionError if fahrenheit is null
 */
privatestaticvoiddisplayTable(doublefahrenheit){
assertfahrenheit>=ABSOLUTE_ZERO:"fahrenheit less than absolute zero";

System.out.println("F\tC");
doublestart=((int)(fahrenheit/10))*10;
for(fahrenheit=start;fahrenheit<start+11;fahrenheit++){
System.out.print(String.format(
"%1$.1f\t",
fahrenheit));
System.out.println(String.format(
"%1$.1f",
fahrenheitToCelsius(fahrenheit)));
}
System.out.println();
}
}

Try It

See Also