Calculating SHA 3 Hash in Java

The common Java reference implementation for crypto and crypto support is probably BouncyCastle. It can be a big library to bring in, which is why we often reach into sun.security (rightly or wrongly.)

Anyway, BouncyCastle seems to offer org.bouncycastle.jcajce.provider.digest.SHA3.DigestSHA3

you can see Implementation in Java

sha3 example

Thanks to @jdv for his answer. I'm adding more information to have a quick start and an example.

First, add the BouncyCastle maven dependency, or get it on Maven Central :

    <dependency>
        <groupId>org.bouncycastle</groupId>
        <artifactId>bcpkix-jdk15on</artifactId>
        <version>1.56</version>
    </dependency>

Then we can test it :

import org.bouncycastle.jcajce.provider.digest.SHA3;
import org.bouncycastle.util.encoders.Hex;
import org.junit.Test;

@Test
public void testSha3() throws Exception {
    String input = "Hello world !";
    SHA3.DigestSHA3 digestSHA3 = new SHA3.Digest512();
    byte[] digest = digestSHA3.digest(input.getBytes());

    System.out.println("SHA3-512 = " + Hex.toHexString(digest));
}

You'll get this result (512 bits or 64 bytes in hexadecimal) :

SHA3-512 = e9a4fd120d684537d57f314d51213ce5acef8ff6974e2b7599674ef0f0a3cf111f0d26ed602db946739da448210fb76a7621d7a8f07728372b10a975f36d8e37

You can compare it with this result : https://duckduckgo.com/?q=sha3+%22Hello+world+!%22&ia=answer