Java: Formatting byte size to human readable format

Here’s how to convert 1000 to "1 kB", 1000000 to "1 MB" etc.

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 input/output:

Input Decimal (SI) Binary (IEC)
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"

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