The JDK 1.5 increases the support of IPv6. It keeps all the functionalities introduced with the JDK 1.4 and provides some new features.

Arguably, the major enhancement resides in the introduction in the socket API of the method setPerformancePreference. This method allows the application to express its own preferences to tune the performance characteristics of this socket. Performance preferences are described by three integers whose values indicate the relative importance of short connection time, low latency, and high bandwidth. With this method, the network oriented notion of Quality of Service (QoS) is introduced. Any application can set its preferences to adapt its network traffic and provide the best QoS.