How to Hash a String with SHA-256 in Java: A Step-by-Step Guide

Hashing a String with SHA-256 in Java: Unraveling the Encoding Enigma

Hashing algorithms, like SHA-256, are not encoding mechanisms; they're one-way irreversible functions. To hash a string with SHA-256 in Java, follow these steps:

1. Encode the String as Bytes: Convert the string into a byte array using a specific character encoding, such as StandardCharsets.UTF_8. This step transforms the textual string into a binary representation.
2. Calculate the Hash: Instantiate a MessageDigest object using the "SHA-256" algorithm. Invoke the digest method on this object, passing the byte array created in step 1. The result is a byte array containing the hashed representation.
3. Converting to String: The hashed data is a binary value, so to represent it as a string, consider either base64 or hexadecimal encoding. Do not attempt to use the String(byte[], String) constructor, as this will lead to incorrect string representation.

For a practical example:

<code class="java">MessageDigest digest = MessageDigest.getInstance("SHA-256");
byte[] hash = digest.digest(text.getBytes(StandardCharsets.UTF_8));</code>

This snippet demonstrates how to obtain the SHA-256 hash of a string in Java. Remember that hashing provides irreversible data transformation, typically used for cryptographic purposes or ensuring data integrity.

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