Applications do not need to explicitly load the org.postgresql.Driver class because the pgjdbc driver jar supports the Java Service Provider mechanism. The driver will be loaded by the JVM when the application connects to PostgreSQL™ (as long as the driver's jar file is on the classpath).
Prior to Java 1.6, the driver had to be loaded by the application - either by calling
or by passing the driver class name as a JVM parameter.
java -Djdbc.drivers=org.postgresql.Driver example.ImageViewer
These older methods of loading the driver are still supported but they are no longer necessary.