String passwort="passwort";
InputStream stream = new ByteArrayInputStream(passwort
        .getBytes(StandardCharsets.UTF_8));
// oder, um einen Hash für eine Datei zu bestimmen:
// InputStream stream = new FileInputStream("D:\\test.png");
try {
    // SHA-1, MD5 oder SHA-256
    System.out.println(Hash.checksum(stream, "SHA-256"));
} catch (Exception e) {
    e.printStackTrace();
}
Java

import java.io.InputStream;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import javax.xml.bind.DatatypeConverter;

public class Hash {
    public static String checksum(InputStream content,
            String hashFunction) throws Exception {

        byte[] buffer = new byte[8192];
        MessageDigest md = MessageDigest.getInstance(hashFunction);

        try (DigestInputStream dis = new DigestInputStream(content, md)) {
            while (dis.read(buffer) != -1);
        }
        return DatatypeConverter.printHexBinary(md.digest());
    }
}
Java