How to Convert a String to Hexadecimal and Back in Java?

Converting a String to Hexadecimal in Java

When working with binary data or cryptography, converting a string to its hexadecimal representation becomes essential. In Java, this conversion process can be accomplished using the String class and the BigInteger class.

To convert a string to hexadecimal, you can use the following steps:

1. Convert the string to a byte array using the getBytes() method:

   byte[] bytes = myString.getBytes(/*YOUR_CHARSET?*/);

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2. Use the BigInteger constructor to create a new BigInteger object from the byte array:

   BigInteger bi = new BigInteger(1, bytes);

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3. Use the format() method of the String class to format the BigInteger object as a hexadecimal string:

   String hexString = String.format("%040x", bi);

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The resulting hexString will be a 40-character hexadecimal representation of the original string.

Converting a Hexadecimal String Back to a String

The process of converting a hexadecimal string back to a string is similar to the above process, but in reverse.

1. Convert the hexadecimal string to a BigInteger object using the BigInteger constructor:

   BigInteger bi = new BigInteger(hexString, 16);

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2. Use the getBytes() method of the BigInteger class to convert the BigInteger object to a byte array:

   byte[] bytes = bi.getBytes();

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3. Use the String constructor to create a new String object from the byte array:

   String myString = new String(bytes);

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The resulting myString will be the original string that was converted to hexadecimal.

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