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;

    DecimalFormat dec = new DecimalFormat("0.00");

    if (k>0)
    {

        hrSize = dec.format(k).concat("KB");

    }
    if (m>0)
    {

        hrSize = dec.format(m).concat("MB");
    }
    if (g>0)
    {

        hrSize = dec.format(g).concat("GB");
    }
    if (t>0)
    {

        hrSize = dec.format(t).concat("TB");
    }

    return hrSize;
    }

This is a method that should return size in GB,MB, KB or TB. Input value is in KB. for example result for 1245 should be like 1.21MB but what I get is 1.00MB.

Answer 1

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 2

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.