javaformattingapache-commons

How can I convert byte size into a human-readable format in Java?


How can I convert byte size into a human-readable format in Java?

Like 1024 should become "1 Kb" and 1024*1024 should become "1 Mb".

I am kind of sick of writing this utility method for each project. Is there a static method in Apache Commons for this?


Solution

  • 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 Ki = 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());
    }
    

    Example output:

                                 SI     BINARY
    
                      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
                 110592:   110.6 kB  108.0 KiB
                7077888:     7.1 MB    6.8 MiB
              452984832:   453.0 MB  432.0 MiB
            28991029248:    29.0 GB   27.0 GiB
          1855425871872:     1.9 TB    1.7 TiB
    9223372036854775807:     9.2 EB    8.0 EiB   (Long.MAX_VALUE)