Converting KB to MB, GB, TB dynamically

Question

public String size(int size){
    String hrSize = \"\";
    int k = size;
    double m = size/1024;
    double g = size/1048576;
    double t = size/1073741824;

            


        

Answer 1

Its not easy to get that right. Rohit Jain mentioned the integer operation. Also rounding can be an issue, as always rounding down may not be desirable. I would advise to go for an available solution like in the triava library.

It can format numbers with arbitrary precision, in 3 different systems (SI, IEC, JEDEC) and various output options. Here are some code examples from the triava unit tests:

UnitFormatter.formatAsUnit(1126, UnitSystem.SI, "B");
// = "1.13kB"
UnitFormatter.formatAsUnit(2094, UnitSystem.IEC, "B");
// = "2.04KiB"

Printing exact kilo, mega values (here with W = Watt):

UnitFormatter.formatAsUnits(12_000_678, UnitSystem.SI, "W", ", ");
// = "12MW, 678W"

You can pass a DecimalFormat to customize the output:

UnitFormatter.formatAsUnit(2085, UnitSystem.IEC, "B", new DecimalFormat("0.0000"));
// = "2.0361KiB"

For arbitrary operations on kilo or mega values, you can split them into components:

UnitComponent uc = new  UnitComponent(123_345_567_789L, UnitSystem.SI);
int kilos = uc.kilo(); // 567
int gigas = uc.giga(); // 123

Answer 2

A modified version. Only calls format once. Includes "Bytes".

public static String formatFileSize(long size) {
    String hrSize = null;

    double b = size;
    double k = size/1024.0;
    double m = ((size/1024.0)/1024.0);
    double g = (((size/1024.0)/1024.0)/1024.0);
    double t = ((((size/1024.0)/1024.0)/1024.0)/1024.0);

    DecimalFormat dec = new DecimalFormat("0.00");

    if ( t>1 ) {
        hrSize = dec.format(t).concat(" TB");
    } else if ( g>1 ) {
        hrSize = dec.format(g).concat(" GB");
    } else if ( m>1 ) {
        hrSize = dec.format(m).concat(" MB");
    } else if ( k>1 ) {
        hrSize = dec.format(k).concat(" KB");
    } else {
        hrSize = dec.format(b).concat(" Bytes");
    }

    return hrSize;
}

Answer 3

class ConverterUtils{
    public static void main(String[] args) {
        System.out.println(getSize(1234567));
    }
    public static String getSize(long size) {
        String s = "";
        double kb = size / 1024;
        double mb = kb / 1024;
        double gb = mb / 1024;
        double tb = gb / 1024;
        if(size < 1024L) {
            s = size + " Bytes";
        } else if(size >= 1024 && size < (1024L * 1024)) {
            s =  String.format("%.2f", kb) + " KB";
        } else if(size >= (1024L * 1024) && size < (1024L * 1024 * 1024)) {
            s = String.format("%.2f", mb) + " MB";
        } else if(size >= (1024L * 1024 * 1024) && size < (1024L * 1024 * 1024 * 1024)) {
            s = String.format("%.2f", gb) + " GB";
        } else if(size >= (1024L * 1024 * 1024 * 1024)) {
            s = String.format("%.2f", tb) + " TB";
        }
        return s;
    }
}

To better understand - https://www.techspot.com/news/68482-quickly-convert-between-storage-size-units-kb-mb.html

Answer 4

I love this:

public static String getDynamicSpace(long diskSpaceUsed)
{
    if (diskSpaceUsed <= 0) {
        return "0";
    }

    final String[] units = new String[] { "B", "KiB", "MiB", "GiB", "TiB" };
    int digitGroups = (int) (Math.log10(diskSpaceUsed) / Math.log10(1024));
    return new DecimalFormat("#,##0.#").format(diskSpaceUsed / Math.pow(1024, digitGroups))
            + " " + units[digitGroups];
}

Answer 5

bickster's answer works quite alright but the problem with it is that it returns results like 45.00 Bytes and 12.00 KB. In my opinion, the last decimal digits should be removed if they are zeros. So instead of 45.00 Bytes and 12.00 KB, you get 45 B and 12 KB (notice that Bytes has been changed to B. This is just for uniformity since we have KB, MB etc and not Kilobytes, Megabytes etc).

private boolean isDouble(double value) {
        if (value % 1 == 0) {
            Log.d(TAG, "value is " + value + " and is not double");
            return false;
        } else {
            Log.d(TAG, "value is " + value + " and is double");
            return true;
        }
    }

The above method simply checks if the value has zeros as decimal digits.

private String formatFileSize(long size) {
        String hrSize = null;
        double b = size;
        double k = size/1024.0;
        double m = ((size/1024.0)/1024.0);
        double g = (((size/1024.0)/1024.0)/1024.0);
        double t = ((((size/1024.0)/1024.0)/1024.0)/1024.0);

        DecimalFormat dec1 = new DecimalFormat("0.00");
        DecimalFormat dec2 = new DecimalFormat("0");
        if (t>1) {
            hrSize = isDouble(t) ? dec1.format(t).concat(" TB") : dec2.format(t).concat(" TB");
        } else if (g>1) {
            hrSize = isDouble(g) ? dec1.format(g).concat(" GB") : dec2.format(g).concat(" GB");
        } else if (m>1) {
            hrSize = isDouble(m) ? dec1.format(m).concat(" MB") : dec2.format(m).concat(" MB");
        } else if (k>1) {
            hrSize = isDouble(k) ? dec1.format(k).concat(" KB") : dec2.format(k).concat(" KB");
        } else {
            hrSize = isDouble(b) ? dec1.format(b).concat(" B") : dec2.format(b).concat(" B");
        }
        return hrSize;
    }

Answer 6

You are performing integer division. So the result of division is also integer. And fractional part is truncated.

so, 1245 / 1024 = 1

Change your division to floating point division: -

double m = size/1024.0;
double g = size/1048576.0;
double t = size/1073741824.0;

Also, your comparison is faulty. You should do the comparison with 1.

if (m > 1), if (t > 1), if (g > 1)

Ideally I would change your comparison to: -

    if (t > 1) {
        hrSize = dec.format(t).concat("TB");
    } else if (g > 1) {
        hrSize = dec.format(g).concat("GB");
    } else if (m > 1) {
        hrSize = dec.format(m).concat("MB");
    } else {
        hrSize = dec.format(size).concat("KB");
    }

You need to compare with the higher unit first, and then move to the lower one.