Rounding of very large floats in Java

Question

Java:

float big = (float) 1e12;
float ulp = Math.ulp(big);

float result = (big + 2/3*ulp) - big;

result is 0.0, while I was expecting ulp (65536.0). Can somebody explain why?

Answer 1

This is because 2/3 = 0 (integer division), try 2.0 / 3

Answer 2

You may try this:

float result = (big + 2f/3*ulp) - big;

ie, you need to typecast the division values else integer/integer will result to zero.

Answer 3

Try typecasting either 2 or 3 to float and try, as 2/3=0, thats why result=0.0