Java: Calculations returning wrong answer? [duplicate]

Answer 1

Floating point notations have limited degrees of accuracy. Here's a guide: http://floating-point-gui.de/

Answer 2

Most floating point calculations involve rounding errors. In your case, there are two rounding errors: converting (decimal) 1.1 to floating point (there's no exact representation for 1.1 in IEEE 754 floating point--which is what Java uses) and then multiplying by 100. See the excellent article What Every Computer Scientist Should Know About Floating-Point Arithmetic for more info.

Answer 3

In 100*1.1 the 1.1 is not qualified and so by default is double while 100 is by default int.
So the result of the multiplication is also double due to the upcast of 100 and that is why you get this result.

Answer 4

As answered, it becomes double hence the format. To print the closest int/long value, better to use Math.round() function as :

 System.out.println(Math.round(100*1.1));

This becomes important when you are multiplying with more precise numbers e.g.

    System.out.println(Math.round(100*1.199));  //--> prints 112
    System.out.println((int)(100*1.199)); //--> prints 111