The ode compiles fine. That means int is imlpicitly castedto float. I what to know why this happens? Although both are 32 bits but then in float some bits may be reserved for the decimal part. Doesn't that leave a float with less number of bits for the integral part?

as i understand it, the specification for floats basically reserves part of the 32 bits for the mantissa (all the numbers regardless of where the decimal point is), and part for the exponent. it's sort of like scientific notation. in other words, the values are stored something like

123456 04

would be 1234.56

123456 06

would be 123456.0

123456 18

would be 123456000000000000.0

as the number get very large, like my last example, there are actually larger and larger 'gaps' between values that can be stored. for all practiacl purposes, there is no difference between 123456000000000000.0 and 123456000000000001.0.

so, yes, there are fewer bits for the mantissa, but that's a trade off we make for being able to store floats.

does that help?

There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors

Just keep in mind that you need not know all of these details for the SCJP exam. Knowing that casting from an int to a float is a widening conversion is enough for the exam.