Question

Why does:

System.out.println((3 + 7 + 10) * (1000 - 8) / (992 - 17))

print 3 and not 20?

System.out.println (2.0 + 1.0/2 + 1.0/6 + 1.0/24 + 1.0/120)

print 2.7166666666666663 and not 2.716666667?

System.out.println (2147483647 + 1)

print -2147483648 and not 2147483648?

Answer 1

System.out.println((3 + 7 + 10) * (1000 – 8) / 992 – 17) print 3 and not 20?

Order of operations. Evaluate the parenthesis first to get (20) * (992) / 992 – 17. Then, multiplication and division from left to right to get 20 – 17. Finally, subtraction to get 3.

System.out.println (2.0 + 1.0/2 + 1.0/6 + 1.0/24 + 1.0/120) print 2.7166666666666663 and not 2.716666667?

Floating point arithmetic. There are lots of questions here on Stack Overflow about floating point math, and a quick Google search will probably turn up more than you could ever need. The Wikipedia article might be a good start, though.

System.out.println (2147483647 + 1) print -2147483648 and not 2147483648?

Overflow. The maximum value of an integer in Java is 2^31 – 1 or 2,147,483,647. When you add one to that value, it wraps around to the value you see. It has to do with the binary representation of the value using 2s compliment.