double field type declaration as zero

Question

What is significant difference between following zero double variable declaration: 0.0 VS 0d

double d1 = 0.0;
double d2 = 0d;

I understand that both these are better than just 0,because are more obvious for code reader.

However 0.0 VS 0d difference is not clear for me.

Answer 1

There is no difference. Have a look at the Java Language Specification, section 3.10.2

DecimalFloatingPointLiteral:

1. Digits . Digits_opt ExponentPart_opt FloatTypeSuffix_opt
2. . Digits ExponentPart_opt FloatTypeSuffix_opt
3. Digits ExponentPart FloatTypeSuffix_opt
4. Digits ExponentPart_opt FloatTypeSuffix

...

FloatTypeSuffix: one of

f F d D

Both are a DecimalFloatingPointLiteral, the first one type 1, the second one type 4