The core module handles cluster connectivity and request execution. It is published under the following coordinates:

<dependency>
  <groupId>com.datastax.oss</groupId>
  <artifactId>java-driver-core</artifactId>
  <version>4.0.0-alpha1</version>
</dependency>

Here's a short program that connects to Cassandra and executes a query:

try (Cluster cluster =
    Cluster.builder().addContactPoint(new InetSocketAddress("127.0.0.1", 9042)).build()) { // (1)

  Session session = cluster.connect();                                                  // (2)

  ResultSet rs = session.execute("select release_version from system.local");              // (3)
  Row row = rs.iterator().next();
  System.out.println(row.getString("release_version"));                                    // (4)
}

1. the Cluster is the main entry point of the driver. It holds the known state of the actual Cassandra cluster. It is thread-safe, you should create a single instance (per target Cassandra cluster), and share it throughout your application;
2. the Session is what you use to execute queries. Likewise, it is thread-safe and should be reused;
3. we use execute to send a query to Cassandra. This returns a ResultSet, which is an iterable of Row objects. On the next line, we extract the first row (which is the only one in this case);
4. we extract the value of the first (and only) column from the row.

Always close the Cluster once you're done with it, in order to free underlying resources (TCP connections, thread pools...). Closing a Cluster also closes any Session that was created from it. In this simple example, we can use a try-with-resources block because Cluster implements java.lang.AutoCloseable; in a real application, you'll probably call one of the close methods (close, closeAsync, forceCloseAsync) explicitly.

Sometimes the driver has to infer a CQL type from a Java type (for example when handling the values of simple statements); for those that have multiple CQL equivalents, it makes the following choices:

• java.lang.String: text
• long: bigint
• java.util.UUID: uuid