Question

what is the difference between double and float type in java?

Answer 1

well if memory serves me right a double has a decimal point 1.0 and a float is a floating point number you will have to look that up because I believe you have to calculate it to get one. I do know floating point numbers are responsible for personal computers working when they were first developed.

Answer 2

It is the capacity of precision, so to speak. Both are "real" numbers (if we think mathematically), but floats have more limited precision. If my memory serves me right, float has 7 digits of precision, while a double has 15. But that may be wrong. Also, note that you have to explicit cast the conversion from double to float. Code like:
float x = (float) 3.14;
or
float x = 3.14f;
is neccessary, or at least it was.

Answer 3

float is 32 bits, double is 64 bits. So obviously, you can store the value of PI with much more precesion in a double type variable than in a float variable.