Why are there so many floats in the Android API?

Question

The default floating point type in Java is the double. If you hard code a constant like 2.5 into your program, Java makes it a double automatically. When you do a

Answer 1

On devices without an FPU, the single-precision floating point ops are much faster than the double-precision equivalents. Because of this, the Android framework provides a FloatMath class that replicates some java.lang.Math functions, but with float arguments instead of double.

On recent Android devices with an FPU, the time required for single- and double-precision operations is about the same, and is significantly faster than the software implementation. (The "Designing for Performance" page was written for the G1, and needs to be updated to reflect various changes.)

Incidentally, writing "2.5f" or "(float) 2.5" doesn't matter. Either way, javac knows you want a single-precision float constant, and that's what it generates. You can verify this by writing a sample program and examining the bytecode generated.