How to convert byte size into human readable format in java

20 May 2016
ADM

human readable format

bytes

java

How to convert byte size into human readable format in java - images/logos/java.jpg

When you need to display informations about files or disk free/used space is useful to convert the bytes size in a human readable format.

Conversion table
Name	Symbol	Binary	Number of bytes	Equal to
Kilobyte	KB	2¹⁰	1,024	1024 B
Megabyte	MB	2²⁰	1,048,576	1024 KB
Gigabyte	GB	2³⁰	1,073,741,824	1024 MB
Terabyte	TB	2⁴⁰	1,099,511,627,776	1024 GB
Petabyte	PB	2⁵⁰	1,125,899,906,842,624	1024 TB
Exabyte	EB	2⁶⁰	1,152,921,504,606,846,976	1024 PB
Zettabyte	ZB	2⁷⁰	1,180,591,620,717,411,303,424	1024 EB
Yottabyte	YB	2⁸⁰	1,208,925,819,614,629,174,706,176	1024 ZB

Example

Here is a simple Java method to convert bytes in human readable format.

package com.admfactory.io;

public class ByteSizeHumanReadable {

    /**
     * Method to format bytes in human readable format
     * 
     * @param bytes
     *            - the value in bytes
     * @param digits
     *            - number of decimals to be displayed
     * @return human readable format string
     */
    public static String format(double bytes, int digits) {
        String[] dictionary = { "bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" };
        int index = 0;
        for (index = 0; index < dictionary.length; index++) {
            if (bytes < 1024) {
                break;
            }
            bytes = bytes / 1024;
        }
        return String.format("%." + digits + "f", bytes) + " " + dictionary[index];
    }

    public static void main(String[] args) {
        long n1 = 12345678L;
        long n2 = 98745678245L;
        long n3 = Long.MAX_VALUE;
        System.out.println("Test byte human reabable format");
        System.out.println();
        System.out.println("n1: " + n1 + " ==> 2 decimals: " + format(n1, 2));
        System.out.println("n1: " + n1 + " ==> 3 decimals: " + format(n1, 3));
        System.out.println();
        System.out.println("n2: " + n2 + " ==> 2 decimals: " + format(n2, 2));
        System.out.println("n2: " + n2 + " ==> 3 decimals: " + format(n2, 3));
        System.out.println();
        System.out.println("n3: " + n2 + " ==> 2 decimals: " + format(n3, 2));
        System.out.println("n3: " + n2 + " ==> 3 decimals: " + format(n3, 3));
    }
}

Output

Test byte human reabable format

n1: 12345678 ==> 2 decimals: 11.77 MB
n1: 12345678 ==> 3 decimals: 11.774 MB

n2: 98745678245 ==> 2 decimals: 91.96 GB
n2: 98745678245 ==> 3 decimals: 91.964 GB

n3: 98745678245 ==> 2 decimals: 8.00 EB
n3: 98745678245 ==> 3 decimals: 8.000 EB