conversion from decimal to hexadecimal and vice versa

Here is a code that converts decimal to hexadecimal.

 import java.io.*;

public class DecimalToHexadecimal{
  public static void main(String[] args) throws IOException{  
  BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
  System.out.println("Enter the decimal value:");
  String hex = bf.readLine();
  int i = Integer.parseInt(hex);
  String hex1 = Integer.toHexString(i);
  System.out.println("Hexa decimal: " + hex1);
  }
}

Here is a code that converts hexadecimal to decimal.

 import java.io.*;

public class  HexadecimalToDecimal{
  public static void main(String[] args) throws IOException{
  BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
  System.out.println("Enter the Hexadecimal number:");
  String str= bf.readLine();
  int i= Integer.parseInt(str,16);
  System.out.println("Decimal:="+ i);
  }
}

thank yoy sir.can i get the code without using standard libraries