Why is the letter f used at the end of a float no.?

Question

I just wanted some information about this.

float n = 2.99944323200023f

What does the f at the end of the literal do? What is i

Answer 1

From the Oracle Java Tutorial, section Primitive Data Types under Floating-Point Literals

A floating-point literal is of type float if it ends with the letter F or f; otherwise its type is double and it can optionally end with the letter D or d.

Answer 2

The f indicates it's a floating point literal, not a double literal (which it would implicitly be otherwise.) It hasn't got a particular technical name that I know of - I tend to call it the "letter suffix" if I need to refer to it specifically, though that's somewhat arbitrary!

For instance:

float f = 3.14f; //Compiles
float f = 3.14;   //Doesn't compile, because you're trying to put a double literal in a float without a cast.

You could of course do:

float f = (float)3.14;

...which accomplishes near enough the same thing, but the F is a neater, more concise way of showing it.

Why was double chosen as the default rather than float? Well, these days the memory requirements of a double over a float aren't an issue in 99% of cases, and the extra accuracy they provide is beneficial in a lot of cases - so you could argue that's the sensible default.

Note that you can explicitly show a decimal literal as a double by putting a d at the end also:

double d = 3.14d;

...but because it's a double value anyway, this has no effect. Some people might argue for it advocating it's clearer what literal type you mean, but personally I think it just clutters code (unless perhaps you have a lot of float literals hanging around and you want to emphasise that this literal is indeed meant to be a double, and the omission of the f isn't just a bug.)

Answer 3

When you write 1.0, it's ambiguous as to whether you intend the literal to be a float or double. By writing 1.0f, you're telling Java that you intend the literal to be a float, while using 1.0d specifies that it should be a double (which is also default if you do not specify that explicitely).

Answer 4

It's to distinguish between floating point and double precision numbers. The latter has no suffix.

Answer 5

In Java, when you type a decimal number as 3.6, its interpreted as a double. double is a 64-bit precision IEEE 754 floating point, while floatis a 32-bit precision IEEE 754 floating point. As a float is less precise than a double, the conversion cannot be performed implicitly.

If you want to create a float, you should end your number with f (i.e.: 3.6f).

For more explanation, see the primitive data types definition of the Java tutorial.

Answer 6

It means that it's a single precision floating point literal rather than double precision. Otherwise, you'd have to write float n = (float)2.99944323200023; to cast the double to single.