Java – Convert File to Hex

This article shows how to convert a file into a hexadecimal (hex) representative format.

for example, below is a text file.

/path/to/text.txt

ABCDEFG
12345678
!@#$%^&*()
Testing only

And we will convert the above file into the following hex format.

41 42 43 44 45 46 47 0D 0A 31 32 33 34 35 36                 | ABCDEFG..123456
37 38 0D 0A 21 40 23 24 25 5E 26 2A 28 29 0D                 | 78..!@#$%^&*().
0A 54 65 73 74 69 6E 67 20 6F 6E 6C 79                       | .Testing only

1. Java Convert File to Hex

The idea is to read the file into an InputStream and uses String.format(%X) to convert each byte into a hex code.

FileToHex.java

package com.favtuts.io.howto;

import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class FileToHex {

    private static final String NEW_LINE = System.lineSeparator();
    private static final String UNKNOWN_CHARACTER = ".";

    public static void main(String[] args) throws IOException {

        String file = "/home/tvt/workspace/favtuts/text.txt";

        String s = convertFileToHex(Paths.get(file));
        System.out.println(s);
    }

    public static String convertFileToHex(Path path) throws IOException {

        if (Files.notExists(path)) {
            throw new IllegalArgumentException("File not found! " + path);
        }

        StringBuilder result = new StringBuilder();
        StringBuilder hex = new StringBuilder();
        StringBuilder input = new StringBuilder();

        int count = 0;
        int value;

        // path to inputstream....
        try (InputStream inputStream = Files.newInputStream(path)) {

            while ((value = inputStream.read()) != -1) {

                hex.append(String.format("%02X ", value));

                //If the character is unable to convert, just prints a dot "."
                if (!Character.isISOControl(value)) {
                    input.append((char) value);
                } else {
                    input.append(UNKNOWN_CHARACTER);
                }

                // After 15 bytes, reset everything for formatting purpose
                if (count == 14) {
                    result.append(String.format("%-60s | %s%n", hex, input));
                    hex.setLength(0);
                    input.setLength(0);
                    count = 0;
                } else {
                    count++;
                }

            }

            // if the count>0, meaning there is remaining content
            if (count > 0) {
                result.append(String.format("%-60s | %s%n", hex, input));
            }

        }

        return result.toString();
    }
    
}

2. Convert Image file to Hex

Run the above program using an image file.

String file = "/path/to/hello.png";

Output

89 50 4E 47 0D 0A 1A 0A 00 00 00 0D 49 48 44                 | .PNG........IHD
52 00 00 03 11 00 00 01 1E 08 06 00 00 00 F5                 | R.............õ
AE 98 9A 00 00 00 09 70 48 59 73 00 00 12 74                 | ®......pHYs...t
00 00 12 74 01 DE 66 1F 78 00 00 00 07 74 49                 | ...t.Þf.x....tI

//...

20 08 42 4B 88 13 21 08 82 20 08 82 20 08 42                 |  .BK..!.. .. .B
4B FC 7F 0B 00 ED 81 F6 3A 58 EC 00 00 00 00                 | Kü...í.ö:Xì....
49 45 4E 44 AE 42 60 82                                      | IEND®B`.

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-io/howto

References

• WIkipedia – Hexadecimal
• String.format(%X) and hex code
• File JavaDoc
• Path JavaDoc