How to convert byte size into 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. Are there any static methods in Apache Commons for this?

Here is my go at it (no loops and handles both SI units and binary units):

public static String humanReadableByteCount(long bytes, boolean si) {
    int unit = si ? 1000 : 1024;
    if (bytes < unit) return bytes + " B";
    int exp = (int) (Math.log(bytes) / Math.log(unit));
    String pre = (si ? "kMGTPE" : "KMGTPE").charAt(exp-1) + (si ? "" : "i");
    return String.format("%.1f %sB", bytes / Math.pow(unit, exp), pre);
}

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)