CODEWITHSUNDEEP
javamath
ShirazITCo
ShirazITCo

Reputation: 1041

Java parse bytes number over 39.4 GB on a long var bug

I have an app that get ftp disk space. so space given by a number that present how many bytes.

the problem is when i got space over 39.4 GB i can just store 39.4*1024*1024*1024 in a long or double var. so if you have 50 GB it just show you 39.4. whats the solution?

Upvotes: 0

Views: 435

Answers (4)

fmucar
fmucar

Reputation: 14558

See if BigInteger class helps you with your problem

http://download.oracle.com/javase/6/docs/api/java/math/BigInteger.html

EDIT:

Actually as others already mentioned, long value will be able to hold a really big value, it can hold far more than 40gb as a number value

Upvotes: 1

Peter Lawrey
Peter Lawrey

Reputation: 533710

long can record 8 Exa-bytes which is 8 * 1024 * 1024 * 1024 GB (minus one byte ;)

Upvotes: 0

sarnold
sarnold

Reputation: 104080

long can store much larger values -- so there must be something specific in your code. I guessed at what your code is doing, see if this looks familiar:

class Out {
    public static void main(String args[]) {
        long l = 40L * 1024 * 1024 * 1024;
        double d = 40.0 * 1024 * 1024 * 1024;
        System.out.println("long l: " + l + " double d: " + d + "\n");
        return;
    }
}

$ vim Out.java ; javac Out.java ; java Out 
long l: 42949672960 double d: 4.294967296E10

Note that I had to multiply 40L rather than just 40 -- if all integers are given as literal integers, without specific L long annotations, then Java will interpret the entire expression as an int. When testing with and without the L (and multiplying by just 1024 * 1024 * 102, building up to confirming my hypothesis), I found the differences entertaining:

$ vim Out.java ; javac Out.java ; java Out # with only '40'
long l: -16777216 double d: 4.294967296E10

$ vim Out.java ; javac Out.java ; java Out # with '40L'
long l: 4278190080 double d: 4.294967296E10

I hope this helps explain why it is important to specify the types of literal data types in the code.

Upvotes: 3

Ingo
Ingo

Reputation: 36349

Here is the solution for storing an amount greater than 39.4 GB:

final long kb = 1024L;
final long mb = 1024L*kb;
final long gb = 1024L*mb;
long solution = 42L * gb;  // > 39.4 GB in a long

Upvotes: 2

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