Coding conventions for number literal suffix? [closed]

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I did some googleling, but was unable to find a solution to my question.

Are there generally accepted java coding conventions according to double and float declaration?

What syntax is recommended by those guidelines?

      Double d = 1d;
      Double d = 1D;
      Double d = 1.;
      Double d = 1.0;
      Double d = 1.0d;
      Double d = 1.0D;

Same goes for Float and Long and also their primitives.

      Long l = 1l;
      Long l = 1L;

All compile the same, but there are difference in clearness when reading these lines of code. The one with the upper case d seems to be more likely to be read wrong --> "D" could be read as "0" or so.

Answer 1

From the Java Tutorials:

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.

The floating point types (float and double) can also be expressed using E or e (for scientific notation), F or f (32-bit float literal) and D or d (64-bit double literal; this is the default and by convention is omitted).

double d1 = 123.4;
// same value as d1, but in scientific notation
double d2 = 1.234e2;
float f1  = 123.4f;

This tells you that:

• Both D and d have the same meaning - just as you observed
• "By convention [D or d are] omitted" because they are the default

Questions of the type "what is better" are offtopic on StackOverflow since they can't have a correct or incorrect answer, only opinions.

But if you ask for a convention I would tend to follow what I've found above - omit the suffix.

Answer 2

It's really just personal preference and I believe lowercase is more common. It's like indentation, pick something and stick with it.

The Java language spec mentions that captial L is preferred for long values because it's easier to read but it doesn't say anything about f/F or d/D.

Answer 3

You usually use the letter that seperates best from the numbers. I didn't know the reason behind this for quite some time, but I was told that capital letters are more easily seperatable from numbers. imagine you have an "L" for Long:

long x = 10000L

is much clearer than

long x = 10000l

The "l" could be easily mistaken to be a "1".

In your case, you should prefer "d" over "D".