How to convert different values of Farenheit to Celcius in a loop-CodePudding

I am trying to make a for loop in Java that will convert Farenheit to Celcius starting from 30 going to 100 and

Here's what I have:

public static void farenheitToCelcius() {

    double farenheit = 0;

    for(double i = 30; i < 100; i  = 10) {
        double celcius = ((farenheit - 32) *5) / 9;
        System.out.println(celcius);
    }
}

I keep getting -17.777 printed 7 times. Would really appreciate some help here.

CodePudding user response：

In the farenheit to celsius conversion, you use farenheit variable (which remains constant at 0) instead of i.

This would be a correct implementation (assuming the conversion equation is correct):

public static void farenheitToCelcius(){
    //double farenheit = 0;
    for(double i = 30; i < 100; i  = 10){
        double celcius = ((i - 32) *5) / 9;
        System.out.println(celcius);
    }
}

If you want to include ten, make sure the condition is i <= 100 and make i an int to prevent round-off error.

CodePudding user response：

You are not assigning the incremented value, it is always using double farenheit = 0 hence the loop is constantly outputting 17,77 as it is receiving 0 as its parameter

public static void farenheitToCelcius(){

double farenheit = 0;

for(double i = 30; i < 100; i  = 10){
    farenheit = i; // the value needs to be set here otherwise it is always calculating 0
    double celcius = (farenheit - 32) * 5/9;
    System.out.println(celcius);
}
}

CodePudding user response：

The other two Answers are good, but could use improved naming and formatting.

Notice how we made double literals by appending d to each number.

And notice how we took the advice of the Comment above to use a descriptive name (fahrenheit) rather than merely i. This makes our code more self-documenting. In this case, using i is both non-descriptive and misleading as the type here is not an integer.

public class Converters
{
    public static double fahrenheitToCelsius ( final double fahrenheit )
    {
        double celsius = ( fahrenheit - 32d ) * ( 5d / 9d );
        return celsius;
    }
}

And, our loop through some Fahrenheit values.

double start = 30d, end = 100d;
for ( double fahrenheit = start ; fahrenheit <= end ; fahrenheit  = 10 )
{
    double celsius = Converters.fahrenheitToCelsius( fahrenheit );
    System.out.println( "fahrenheit "   fahrenheit   " ⟹ celsius "   celsius );
}

When run.

fahrenheit 30.0 ⟹ celsius -1.1111111111111112
fahrenheit 40.0 ⟹ celsius 4.444444444444445
fahrenheit 50.0 ⟹ celsius 10.0
fahrenheit 60.0 ⟹ celsius 15.555555555555557
fahrenheit 70.0 ⟹ celsius 21.11111111111111
fahrenheit 80.0 ⟹ celsius 26.666666666666668
fahrenheit 90.0 ⟹ celsius 32.22222222222222
fahrenheit 100.0 ⟹ celsius 37.77777777777778

Bonus: You could use streams to write a one-liner. Not that this is an improvement in this case, but FYI.

We use IntStream to generate a sequence of integer numbers while incrementing by ten, convert those to double values, and convert to celsius, while sending each result to the console.

IntStream.iterate( 30 , fahrenheit -> fahrenheit   10 ).limit( ( ( 100 - 30 ) / 10 )   1 ).asDoubleStream().map( Converters :: fahrenheitToCelsius ).forEach( System.out :: println );

Or, reformatted:

IntStream
        .iterate( 30 , fahrenheit -> fahrenheit   10 )
        .limit( ( ( 100 - 30 ) / 10 )   1 )
        .asDoubleStream()
        .map( Converters :: fahrenheitToCelsius )
        .forEach( System.out :: println );

See that code run live at IdeOne.com.

Or write the conversion into that one-liner, rather than call another method.

IntStream
        .iterate( 30 , fahrenheit -> fahrenheit   10 )
        .limit( ( ( 100 - 30 ) / 10 )   1 )
        .asDoubleStream()
        .map( fahrenheit -> ( fahrenheit - 32d ) * ( 5d / 9d ) )
        .forEach( System.out :: println );