Program to reverse the hexadecimal value of elements in a byte array

public class ReverseHexaofByteArray

{

            protected static final byte[] Hexhars =

            {

                        '0', '1', '2', '3', '4', '5',

                        '6', '7', '8', '9', 'a', 'b',

                        'c', 'd', 'e', 'f'

            };

            public static String byteArrayToHexString(byte[] b)

            {                       

StringBuilder st = new StringBuilder(2 * b.length);

                        for (int j = b.length - 1; j > -1; j --)

                        {

                                    int w = b[j] & 0xff;

                                    st.append((char) Hexhars[w >> 4]);

                                    st.append((char) Hexhars[w & 0xf]);

                                    System.out.println(st.toString());

                        }

                        return st.toString();

            }

            public static void main(String[] args)

            {

                        byte[] oBs =

                        {

                                    65, 55, 88

                        };

                        String strResult = byteArrayToHexString(oBs);

                        System.out.println(strResult);

            }

}

Program to convert byte array data to hexadecimal

Program to convert byte array data to hexadecimal

public class ByteArrayDemo

{

             protected static final byte[] Hexhars =

            {

                        '0', '1', '2', '3', '4', '5',

                        '6', '7', '8', '9', 'a', 'b',

                        'c', 'd', 'e', 'f'

            };

           

            public String byteArrayToHexString(byte[] b)

            {

//Constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.

                        StringBuilder s = new StringBuilder(2 * b.length);

                     

                        for (int i = 0; i < b.length; i ++)

                        {

                                    int v = b[i] & 0xff;

                                    /*

                                     * ANDs b[i] with 0xFF

 * The value of b[i] is 65(Whose binary is 01000001), we AND it with 0xFF(whose Binary is 11111111)

                                     * resulting in the binary 01000001

                                     */

                                    s.append((char) Hexhars[v >> 4]);

                                    /*

                                     * v >> 4 - Right shifts the value of v(01000001) to 4 places

                                     * On 1st right shift, we get 00100000

                                    * On 2nd right shift, we get 00010000

                                    * On 3rd right shift, we get 00001000

                                    * On 4th right shift, we get 00000100

                                    * Which is 4

* Hexhars[4] - Finds the value at the 4th place(starting from 0) from the byte array Hexhars

                                    */

                                   

s.append((char) Hexhars[v & 0xf]);

                                    /*

                                     * ANDs b[i] with 0xF

* The value of b[i] is 65(Whose binary is 01000001), we AND it with 0xF(whose Binary is 00001111)

                                    * resulting in the binary 00000001 - 1

                                    * Hexhars[1] - Finds the value at the 1st place from the byte array Hexhars

                                    */

}

                        return s.toString();

            }

           

         

            public static void main(String[] args)

            {

                        byte[] byteArray = new byte[] {65};

                        ByteArrayDemo obyteArrayDemo = new ByteArrayDemo();

                        String sData = obyteArrayDemo.byteArrayToHexString(byteArray);                        

                        System.out.println(sData);                          

            }

}

Java program to insert image as byte array to postgres database

//Program to insert an image into postgres database as byte array

import java.sql.*;
import java.io.*;
import java.util.logging.Level;
import java.util.logging.Logger;

public class insertImage
{
  public static void main(String[] args)
  {
    PreparedStatement statement = null;
    {
      FileInputStream fin = null;
      try
      {
        System.out.println("Insert Image Example!");
        Class.forName("org.postgresql.Driver");
        String url = "jdbc:postgresql://x.x.x.x:5432/MYDB";
        Connection oConnection = DriverManager.getConnection(url, "username", "password");
        System.out.println("Sucessfully connected to Postgres Database");
        File imgfile = new File("myimage.jpg");
        fin = new FileInputStream(imgfile);
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] buf = new byte[1024];
        for (int readNum; (readNum = fin.read(buf)) != -1;)
        {
          bos.write(buf, 0, readNum);
          byte[] bytes = bos.toByteArray();
          String sql = "INSERT INTO my_table (byte_array) VALUES (?)";
          statement = oConnection.prepareStatement(sql);
          statement.setBytes(1, bytes);
          statement.executeUpdate();
          System.out.println("Image inserted into database!");

        }
        statement.close();
        oConnection.close();
      }
      catch (Exception ex)
      {
        System.out.println("Exception:- " + ex);
      }
      try
      {
        fin.close();
      }
      catch (IOException ex)
      {
        System.out.println(" IOException:- " + ex);
      }
    }
  }
}