Java: SHA-256 hashing for integrity

A cryptographic hash function turns any input into a fixed-size digest. It is deterministic, one-way, and designed so that a tiny change in the input changes the digest unpredictably. SHA-256 produces 32 bytes, shown here as 64 hexadecimal characters.

Java

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;

class Main {
  static String hex(byte[] bytes) {
    StringBuilder sb = new StringBuilder();
    for (byte b : bytes) {
      sb.append(String.format("%02x", b));
    }
    return sb.toString();
  }

  public static void main(String[] args) throws Exception {
    MessageDigest sha = MessageDigest.getInstance("SHA-256");
    String a = hex(sha.digest("abc".getBytes(StandardCharsets.UTF_8)));
    String b = hex(sha.digest("abd".getBytes(StandardCharsets.UTF_8)));
    System.out.println(a);
    System.out.println(b);
    System.out.println(MessageDigest.isEqual(a.getBytes(StandardCharsets.UTF_8), a.getBytes(StandardCharsets.UTF_8)));
  }
}

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