Variable may not of been initialized even though it has been in the method

Your only problem is that you didn’t initialize temperature, celsius, or farenheit.
When making your variables here:
double celsius,fahrenheit,temperature,inFahrenheit,inCelsius;, you need to make temperature equal to something, say 20.
I would recommend to take out the ints celsius and farenheit, or set them equal to the doubles Celsius and Farenheit, that you set equal to temperature…math.