How to create a long value with all bits = 1

Question

I tried the following:

public static final long DEVICE_ID_UNKNOWN = 0xFFFFFFFFFFFFFFFF;

but it causes

The literal 0xFFFFFFFFFFFFFFFF of type int is out of range

possible duplicate of [Initialize a long in Java](http://stackoverflow.com/questions/6834037/initialize-a-long-in-java) — MByD, Dec 20 '11 at 10:09

score 8 · Accepted Answer · answered Dec 20 '11 at 10:09

8

Use 0xFFFFFFFFFFFFFFFFl and be fine. Another way would be to use simply -1 because this value also has all bits set. See http://en.wikipedia.org/wiki/Two%27s_complement for details.

answered Dec 20 '11 at 10:09

A.H.

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score 7 · Answer 2 · answered Dec 20 '11 at 10:11

7

You need to specify the type of the number if it can not be represented as an int. A long is a L or l (lowercase). I prefer uppercase as lowercase is easy to mistake for 1 (one).

public static final long DEVICE_ID_UNKNOWN = 0xFFFFFFFFFFFFFFFFL;

Or, you can just set the value to -1, but that might not be as clear in communicating the meaning "all bits 1".

answered Dec 20 '11 at 10:11

Roger Lindsjö

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+1 imho best answer (extra pluses: upper case L over lower case l; hex notation over `-1` in this case) – Fabian Barney Dec 20 '11 at 10:15

score 6 · Answer 3 · answered Dec 20 '11 at 10:13

6

You may use either of the following:

public static final long DEVICE_ID_UNKNOWN = 0xFFFFFFFFFFFFFFFFL;

or

public static final long DEVICE_ID_UNKNOWN = ~0L;

or

public static final long DEVICE_ID_UNKNOWN = -1L;

answered Dec 20 '11 at 10:13

Jomoos

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score 3 · Answer 4 · answered Dec 20 '11 at 10:12

3

Yet another way to get all 1s

public static final long DEVICE_ID_UNKNOWN = ~0L;

answered Dec 20 '11 at 10:12

Peter Lawrey

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`~0` means make every bit a 1 (the opposite of 0) whereas -1 happens to be all 1s as a `long` (but not as a `double`) – Peter Lawrey Dec 20 '11 at 11:06
Can you explain? I didn't understand what you mean by 'all 1s as a long (but not as a double)'. – user1071840 May 28 '14 at 14:58
a double has a different bit format than a long - see IEEE 754: http://en.wikipedia.org/wiki/Double-precision_floating-point_format – vazor Feb 18 '15 at 16:51
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I believe this is the easiest alternative to understand. And you don't need to triple-check the number of Fs either. – matiash Nov 11 '16 at 18:48

score 2 · Answer 5 · answered Dec 20 '11 at 10:10

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public static final long DEVICE_ID_UNKNOWN = -1L;

answered Dec 20 '11 at 10:10

Graham Borland

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score 1 · Answer 6 · answered Dec 20 '11 at 10:08

1

Use public static final long DEVICE_ID_UNKNOWN = 0xFFFFFFFFFFFFFFFFL; instead to signify that it's a long value, not an int value.

answered Dec 20 '11 at 10:08

Anthony Grist

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score 1 · Answer 7 · answered Dec 20 '11 at 10:10

1

Sorry, I'm not the java guy, but wouldn't -1 do?

answered Dec 20 '11 at 10:10

Michael Krelin - hacker

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score 1 · Answer 8 · answered Dec 20 '11 at 10:10

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public static final long DEVICE_ID_UNKNOWN = 0xFFFF_FFFF_FFFF_FFFFL;

Usefull reference http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

answered Dec 20 '11 at 10:10

Kiril Kirilov

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+1 Thanks for useful answer but `_` is only in Java SE 7 and later so I will avoid it. – Caner Dec 20 '11 at 10:25

How to create a long value with all bits = 1

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