Coding conventions for number literal suffix? [closed]

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

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.