What was the rationale for allowing underscores between integer digits?

Question

I stumbled across this seemingly odd statement in the JLS, section 3.10.1 (integer literals) today:

Underscores are allowed as separators between digits that denote the integer.

Lo and behold the following is completely valid (example):

int x = 1_2_3_4_5____6;

Underscores may only appear between digits, leading/trailing underscores are invalid.

What was the rationale for this? Is it some holdover from some other language? Some style that was common at the time? It seems like a rather strange thing to allow.

Nevermind. http://stackoverflow.com/questions/18175809/wierd-syntax-underscores-between-digits?rq=1. — Jason C, Mar 02 '17 at 19:19
@Flown Yeah. The dupe says readability too. Deleting this. Or not, now it's answered. (Also huh, there's a whole chain of dupes here that didn't come up in the auto-search. Fun!) — Jason C, Mar 02 '17 at 19:20
*Is it some holdover from some other language?* It was added in Java 7, so no. — shmosel, Mar 02 '17 at 19:25

score 3 · Accepted Answer · answered Mar 02 '17 at 19:19

3

The idea behind this is to be able to display a big number that is easily readable.

Example: int x = 1_000_000;

There are other use cases for this but this is the most used i think.

See the documentation for more information.

answered Mar 02 '17 at 19:19

Jeroen Vandevelde

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Kinda handy. I might start doing that. – Jason C Mar 02 '17 at 19:24
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Whoa there, [keep your pants on](https://i.snag.gy/qIzc6h.jpg). There's a 15 minute time limit on accepts. I might wait until tomorrow just to keep you on the edge of your seat! :D – Jason C Mar 02 '17 at 19:27
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@JeroenVandevelde No need for that. Just write more answers and the points will come. – Thorbjørn Ravn Andersen Mar 02 '17 at 19:46

What was the rationale for allowing underscores between integer digits?

1 Answers1