How to Generate SHA-256 Hashes from Strings in Java?

Java: Hashing Strings with SHA-256

String hashing using SHA-256 is commonly used to ensure data integrity, provide secure password storage, or generate unique identifiers. In Java, this operation can be performed swiftly and easily.

Step 1: Understand the SHA-256 Algorithm

SHA-256 (Secure Hash Algorithm 256) is a one-way cryptographic hash function that produces a fixed-size hash value from an input string. This hash value is unique and cannot be reversed to obtain the original string.

Step 2: Choose an Encoding

SHA-256 works with byte arrays, so before hashing a string, you need to convert it into a byte array. Use an encoding such as UTF-8, which most programming languages support by default.

Step 3: Create a MessageDigest Instance

Use the MessageDigest class to create an instance of the SHA-256 algorithm.

<code class="java">MessageDigest digest = MessageDigest.getInstance("SHA-256");</code>

Step 4: Hash the String

Digesting or hashing the string involves passing the byte array into the digest instance. The result of this operation is the SHA-256 hash value in the form of a byte array.

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

Byte Array to String Conversion

As the hash value is a byte array, you may need to convert it to a more readable format for display or storage. Common options include base64 or hexadecimal.

Example Code

<code class="java">import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;

public class SHA256Hashing {

    public static byte[] hashSHA256(String text) {
        try {
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            return digest.digest(text.getBytes(StandardCharsets.UTF_8));
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }
}</code>

Using the above hashSHA256 method, you can now hash String values easily and securely.

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