jNetPcap is an open-source java library. It contains:
A Java wrapper for nearly all libpcap library native calls
Decodes captured packets in real-time
Provides a large library of network protocols (core protocols)
Users can easily add their own protocol definitions using java SDK
jNetPcap uses a mixture of native and java implementation for optimum packet decoding performance
Is WinPcap supported?
Yes, WinPcap is also supported and all of its windows extensions are available, including remote captures.