Complete list of MessageDigest available in the JDK

To get just the algorithm names, without aliases or any additional information, the simplest is:

import java.security.Security;
import java.util.Set;

...

Set<String> algorithms = Security.getAlgorithms("MessageDigest");

Note that you should configure any non-standard providers before calling this function, e.g. by using Security.addProvider(Provider provider).

since Java 1.4


In addition to JB's answer, I would like to propose a solution that queries the runtime for available algorithms. This method is of course easily converted to one for Cipher, SecureRandom, Mac, KeyAgreement, KeyFactory or any other type of algorithm.

Program

import java.security.MessageDigest;
import java.security.Provider;
import java.security.Provider.Service;
import java.security.Security;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;

public class ShowHashAlgorithms {

    private static final void showHashAlgorithms(Provider prov, Class<?> typeClass) {
        String type = typeClass.getSimpleName();

        List<Service> algos = new ArrayList<>();

        Set<Service> services = prov.getServices();
        for (Service service : services) {
            if (service.getType().equalsIgnoreCase(type)) {
                algos.add(service);
            }
        }

        if (!algos.isEmpty()) {
            System.out.printf(" --- Provider %s, version %.2f --- %n", prov.getName(), prov.getVersion());
            for (Service service : algos) {
                String algo = service.getAlgorithm();
                System.out.printf("Algorithm name: \"%s\"%n", algo);


            }
        }

        // --- find aliases (inefficiently)
        Set<Object> keys = prov.keySet();
        for (Object key : keys) {
            final String prefix = "Alg.Alias." + type + ".";
            if (key.toString().startsWith(prefix)) {
                String value = prov.get(key.toString()).toString();
                System.out.printf("Alias: \"%s\" -> \"%s\"%n",
                        key.toString().substring(prefix.length()),
                        value);
            }
        }
    }

    public static void main(String[] args) {
        Provider[] providers = Security.getProviders();
        for (Provider provider : providers) {
            showHashAlgorithms(provider, MessageDigest.class);
        }
    }
}

Sun provider output

This code will generate the following output for Java 1.8. Note that because of some old mistake by the API providers, the provider version is only present as a double. It is not possible to distinguish between version 1.80 or version 1.8.0 because of this.

The aliases are below the actual implementations. Some of these aliases are Object Identifiers or OID's in dot notation. These OID's are used to indicate algorithms from within ASN.1 encoded data formats such as X5.09v3 certificates as used within SSL/TLS. For instance, 1.3.14.3.2.26 is the dot notation for {iso(1) identified-organization(3) oiw(14) secsig(3) algorithms(2) hashAlgorithmIdentifier(26)} and the alias for SHA/SHA-1.

 --- Provider SUN, version 1.80 --- 
Algorithm name: "MD2"
Algorithm name: "MD5"
Algorithm name: "SHA"
Algorithm name: "SHA-224"
Algorithm name: "SHA-256"
Algorithm name: "SHA-384"
Algorithm name: "SHA-512"
Alias: "SHA-1" -> "SHA"
Alias: "OID.1.3.14.3.2.26" -> "SHA"
Alias: "1.3.14.3.2.26" -> "SHA"
Alias: "OID.2.16.840.1.101.3.4.2.4" -> "SHA-224"
Alias: "OID.2.16.840.1.101.3.4.2.3" -> "SHA-512"
Alias: "OID.2.16.840.1.101.3.4.2.2" -> "SHA-384"
Alias: "OID.2.16.840.1.101.3.4.2.1" -> "SHA-256"
Alias: "2.16.840.1.101.3.4.2.4" -> "SHA-224"
Alias: "2.16.840.1.101.3.4.2.3" -> "SHA-512"
Alias: "2.16.840.1.101.3.4.2.2" -> "SHA-384"
Alias: "2.16.840.1.101.3.4.2.1" -> "SHA-256"
Alias: "SHA1" -> "SHA"

Bouncy Castle provider output

Output for Bouncy Castle (not asked for, included for comparison):

 --- Provider BC, version 1.51 --- 
Algorithm name: "GOST3411"
Algorithm name: "MD2"
Algorithm name: "MD4"
Algorithm name: "MD5"
Algorithm name: "SHA-1"
Algorithm name: "RIPEMD128"
Algorithm name: "RIPEMD160"
Algorithm name: "RIPEMD256"
Algorithm name: "RIPEMD320"
Algorithm name: "SHA-224"
Algorithm name: "SHA-256"
Algorithm name: "SHA-384"
Algorithm name: "SHA-512"
Algorithm name: "SHA-512/224"
Algorithm name: "SHA-512/256"
Algorithm name: "SHA3-224"
Algorithm name: "SHA3-256"
Algorithm name: "SHA3-384"
Algorithm name: "SHA3-512"
Algorithm name: "Skein-256-128"
Algorithm name: "Skein-256-160"
Algorithm name: "Skein-256-224"
Algorithm name: "Skein-256-256"
Algorithm name: "Skein-512-128"
Algorithm name: "Skein-512-160"
Algorithm name: "Skein-512-224"
Algorithm name: "Skein-512-256"
Algorithm name: "Skein-512-384"
Algorithm name: "Skein-512-512"
Algorithm name: "Skein-1024-384"
Algorithm name: "Skein-1024-512"
Algorithm name: "Skein-1024-1024"
Algorithm name: "SM3"
Algorithm name: "TIGER"
Algorithm name: "WHIRLPOOL"
Alias: "SHA256" -> "SHA-256"
Alias: "SHA224" -> "SHA-224"
Alias: "1.3.36.3.2.3" -> "RIPEMD256"
Alias: "1.3.36.3.2.2" -> "RIPEMD128"
Alias: "1.3.36.3.2.1" -> "RIPEMD160"
Alias: "1.2.156.197.1.401" -> "SM3"
Alias: "SHA512" -> "SHA-512"
Alias: "SHA1" -> "SHA-1"
Alias: "GOST" -> "GOST3411"
Alias: "2.16.840.1.101.3.4.2.6" -> "SHA-512/256"
Alias: "2.16.840.1.101.3.4.2.5" -> "SHA-512/224"
Alias: "2.16.840.1.101.3.4.2.4" -> "SHA-224"
Alias: "2.16.840.1.101.3.4.2.3" -> "SHA-512"
Alias: "2.16.840.1.101.3.4.2.2" -> "SHA-384"
Alias: "2.16.840.1.101.3.4.2.1" -> "SHA-256"
Alias: "1.2.643.2.2.9" -> "GOST3411"
Alias: "1.3.14.3.2.26" -> "SHA-1"
Alias: "SHA512/224" -> "SHA-512/224"
Alias: "GOST-3411" -> "GOST3411"
Alias: "SHA512256" -> "SHA-512/256"
Alias: "SHA384" -> "SHA-384"
Alias: "SM3" -> "SM3"
Alias: "SHA" -> "SHA-1"
Alias: "1.2.840.113549.2.5" -> "MD5"
Alias: "1.2.840.113549.2.4" -> "MD4"
Alias: "1.2.840.113549.2.2" -> "MD2"

The documentation says:

These algorithms are described in the MessageDigest section of the Java Cryptography Architecture Standard Algorithm Name Documentation

The linked document contains the following line, right after the table of contents:

Note: The Oracle Providers Documentation contains specific provider and algorithm information.

And the linked document contains the complete list of MessageDigest algorithms provided by each provider.