Getting Byte Size in Human-Readable Format in Java

Converting byte sizes into human-readable formats, such as "1 kB" or "1 MB," is a common task in Java programming. While you may often write your own utility methods for this, there are also reusable solutions available.

Apache Commons Static Methods

The Apache Commons Lang library provides static methods for converting byte sizes:

1. humanReadableByteCountSI: Uses SI units (base 1000) like "GB", "MB", "kB".
2. humanReadableByteCountBin: Uses binary units (base 1024) like "GiB", "MiB", "KiB".

Implementation Details

Here are the implementations of these methods:

SI Units:

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 Units:

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

The following table shows the output for various byte sizes using both SI and Binary methods:

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