Java: incompatible types, possible lossy conversion from double to float

Question

why do I get this error message when i try to compile the following code?

float a = 1/0.1;
System.out.println(a);

or

float b = 1/0.002;
System.out.println(b);

incompatible types: possible lossy conversion from double to float

Am i getting an overflow? I'm looking to understand the theory behind this. Thanks in advance.

Answer 1

Use float literals:

float a = 1f / 0.1f;

Answer 2

0.1 and 0.002 are double literals. Java's double type has more precision than its float type. So, when you convert from double to float , the number may be changed by rounding it to the nearest value representable in float . Using decimal as an analogy, assigning the four-digit.1234 to a two-digit type would produce a different number, .12.

When you do this conversion implicitly, by assignment to a float variable, the compiler tells you there could be a loss of information. By using a cast, you tell the compiler the conversion to a less precise format is intentional. Or by using float literals such as 0.1f and 0.002f , you work with float values throughout and avoid conversion.

Generally, pick one type, float or double and use it throughout your calculations, for both literals and variables.