In Peer-to-Peer (P2P) networks, peers often interact with unknown peers and finding a reliable peer for interaction is a major challenge. In our previous work, we proposed and implemented a fuzzy-based trustworthiness system, which considered only positive effect parameters. In this paper, we propose a new fuzzy-based trustworthiness system for P2P Communications in JXTA-Overlay that decides the Peer Reliability (PR) considering three parameters: Number of Uploads (NU), Peer Disconnections (PD) and Reputation(R). In the proposed system, the NU and PD parameters have negative effect, while R parameter has positive effect for deciding peer reliability. We evaluate the proposed system by computer simulations. The simulation results has shown that the proposed system can effectively help peers to select reliable peers to download information.