Convert byte Array to Hex String in Java

In Java, Converting a byte array to a hex string means transforming each byte into its hexadecimal representation.

• byte array: A byte array is a collection of byte values. Each byte is an 8-bit unit of data.
• Hex String: A hexadecimal (hex) string represents a number in base-16, using digits 0-9 and letters A-F. We represent the A-F in numbers as 10 to 15.

The following is our byte array as given below ?

byte[] b = new byte[]{'p', 'q', 'r'};

We have created a custom method "display" that takes a byte array as input. This method converts the byte array to a hex string.

public static String display(byte[] b1) {
   StringBuilder strBuilder = new StringBuilder();
   for(byte val : b1) {
      strBuilder.append(String.format("%02x", val&0xff));
   }
   return strBuilder.toString();
}

To Convert byte Array to Hex String in Java is quite easy. Let's learn the following methods:

• Using StringBuilder
• Using BigInteger

Converting byteArray to hex string using StringBuilder Class

To convert a byteArray to a hex string We have a StringBuilder class in Java. This class belongs to the java.lang package, used to create and manipulate a string can be modified.

Each byte in the array is converted to a two-digit hexadecimal string and appended to a 'StringBuilder'. The resulting hex string is then returned, with trailing spaces removed.

Example

In this example, we convert a byte array containing ASCII values into a string ("pqr"). Then, it uses a 'StringBuilder' to convert the same byte array into a hexadecimal string representation ("70 71 72").

public class Main {
   public static void main(String args[]) {
      byte[] b = new byte[]{'p', 'q', 'r'};
      /* byte array cannot be displayed as String because it may have non-printable
      characters e.g. 0 is NUL, 5 is ENQ in ASCII format */
      String str = new String(b );
      System.out.println(str);
      // byte array to Hex String
      System.out.println("Byte array to Hex String = " + display(b));
   }

   public static String display(byte[] b1) {
      StringBuilder strBuilder = new StringBuilder();
      for (byte val : b1) {
         strBuilder.append(String.format("%02x ", val & 0xff));
      }
      return strBuilder.toString().trim(); // Remove trailing space
   }
}

Output

The above program produce the following result ?

pqr
Byte array to Hex String = 70 71 72

Converting byteArray to hex string using BigInteger Class

To convert a byteArray into a hex string in Java, we have a BigInteger class that belongs to Java.math package. This package is used to perform mathematical operations on large integers outside the range of the primitive int and long types.

We create a BigInteger object from the byte array and then convert it to a hexadecimal string representation using bigInt.toString(16). This converts the byte array into a hex string format.

Example

This is another example of converting a byte array to a hex string using the BigInteger class. It initializes a BigInteger with the byte array and then converts it to a hex string using the toString(16) method.

import java.math.BigInteger;

public class Main {
   public static void main(String args[]) {
      byte[] b = new byte[]{'p', 'q', 'r'};
      /* byte array cannot be displayed as String because it may have non-printable
      characters e.g. 0 is NUL, 5 is ENQ in ASCII format */
      String str = new String(b);
      System.out.println(str);
      System.out.println("Byte array to Hex String = " + display(b));
   }

   public static String display(byte[] b1) {
      BigInteger bigInt = new BigInteger(1, b1);
      return bigInt.toString(16); 
   }
}

Output

The above program produce the following result ?

pqr
Byte array to Hex String = 707172