Java: Formatting byte size to human readable format
☞
The code in the first version of this article was flawed. The code below is now the recommended solution. See the following article for details:
The most copied StackOverflow snippet of all time is flawed!
SI (1 k = 1,000)
public static String humanReadableByteCountSI(long bytes) {
if (-1000 < bytes && bytes < 1000) {
return bytes + " B";
}
CharacterIterator ci = new StringCharacterIterator("kMGTPE");
while (bytes <= -999_950 || bytes >= 999_950) {
bytes /= 1000;
ci.next();
}
return String.format("%.1f %cB", bytes / 1000.0, ci.current());
}
Binary (1 K = 1,024)
public static String humanReadableByteCountBin(long bytes) {
long absB = bytes == Long.MIN_VALUE ? Long.MAX_VALUE : Math.abs(bytes);
if (absB < 1024) {
return bytes + " B";
}
long value = absB;
CharacterIterator ci = new StringCharacterIterator("KMGTPE");
for (int i = 40; i >= 0 && absB > 0xfffccccccccccccL >> i; i -= 10) {
value >>= 10;
ci.next();
}
value *= Long.signum(bytes);
return String.format("%.1f %ciB", value / 1024.0, ci.current());
}
Examples
| Input | SI 1k = 1000 |
Binary 1k = 1024 |
|---|---|---|
| 0 | 0 B |
0 B |
| 27 | 27 B |
27 B |
| 999 | 999 B |
999 B |
| 1000 | 1.0 kB |
1000 B |
| 1023 | 1.0 kB |
1023 B |
| 1024 | 1.0 kB |
1.0 KiB |
| 1728 | 1.7 kB |
1.7 KiB |
| 1855425871872 | 1.9 TB |
1.7 TiB |
| Long.MAX_VALUE | 9.2 EB |
8.0 EiB |
Comments (6)
For the binary can't you use the shift operator ? like b < 1<<10 ? String.format("%.1f KiB", bytes>>10)
by Pino |
Unfortunately no. The unit should for example go from KiB to MiB as soon as the number of bytes is closer to 10243 than it is to 1023.9×10242. This happens between these two values.
by Andreas Lundblad |
Why use 0xfffccccccccccccL?
by Ma |
Because that is the point at which one should transition from PB to EB. Think of it like this: 0xfffccccccccccccL is to 250 what 999,950,000 is to 109.
These are the international standard symbols used for describing the values you calculate. You should use them and not strings like GiB
by Doug Blake |
GB and GiB are two different notations.
Gis the SI variant and stands, as you say, for giga (10003).Giis the IEC standard and stands for gibi (10243).But I agree, if I were to pick one, I'd go with the SI standard.
by Andreas Lundblad |