CODEWITHSUNDEEP
javajava-7
Samir Mangroliya
Samir Mangroliya

Reputation: 40416

Is there Any End of Underscores in Numeric Literals?

I just read Enhancements in Java7( http://docs.oracle.com/javase/7/docs/technotes/guides/language/underscores-literals.html). In that I see Underscores Numeric Literals and try Like....

int i=9_000; its OK.

But I see rules for that it also allows like...

int i=9____________________________________________________________________________________000;

Is there any end of Underscores?

Upvotes: 3

Views: 622

Answers (4)

kwakeroni
kwakeroni

Reputation: 276

There's no limit. Why should there be ? On the other hand, the only reason I see to use any number of underscores, is to be able to do fancy stuff like in the following piece of code (created by Joshua Bloch, if I'm not mistaken):

private static final int BOND =
     0000_____________0000________0000000000000000__000000000000000000+
   00000000_________00000000______000000000000000__0000000000000000000+
  000____000_______000____000_____000_______0000__00______0+
 000______000_____000______000_____________0000___00______0+
0000______0000___0000______0000___________0000_____0_____0+
0000______0000___0000______0000__________0000___________0+
0000______0000___0000______0000_________0000__0000000000+
0000______0000___0000______0000________0000+
 000______000_____000______000________0000+
  000____000_______000____000_______00000+
   00000000_________00000000_______0000000+
     0000_____________0000________000000007;

Upvotes: 5

paxdiablo
paxdiablo

Reputation: 882286

No, there's no limit. Java allows any amount of underscores although, depending on how your compiler is implemented, you may run into problems for bizarre edge cases like several billion of them :-)

In those places where you can have underscores, the language specification does not limit the quantity. I emphasise "can" there because there are places where they're not allowed, such as before the first digit, after the last, next to the decimal point and so on. But that's a different issue.

However, rather than ask if it's possible, you should instead ask what would be the point of more than one consecutive underscore.

One underscore aids readability by naturally grouping the numbers:

1_000_000
4072_1199_6645_1234
whereas more than one tends to reduce readability:

1_0_0________000_0
4072___________________________11_9_9_6641234

Upvotes: 4

Perception
Perception

Reputation: 80633

Here is the definition of a decimal literal from the JLS:

DecimalNumeral:
    0
    NonZeroDigit Digitsopt
    NonZeroDigit Underscores Digits 

Digits:
    Digit
    Digit DigitsAndUnderscoresopt Digit 

Digit:
    0
    NonZeroDigit

NonZeroDigit: one of
    1 2 3 4 5 6 7 8 9

DigitsAndUnderscores:
    DigitOrUnderscore
    DigitsAndUnderscores DigitOrUnderscore 

DigitOrUnderscore:
    Digit
    _

Underscores:
    _
    Underscores _

Notice the recursive definition for Underscores, fun!

Upvotes: 4

Dave L.
Dave L.

Reputation: 9801

No. Here is the document:

http://docs.oracle.com/javase/7/docs/technotes/guides/language/underscores-literals.html

In Java SE 7 and later, any number of underscore characters (_) can appear anywhere between digits in a numerical literal.

Upvotes: 2

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