Intercepting or dropping packets

[s18924]

Hello,

is there a way to intercept or drop certain packets using this library?
I am writing a project to school where I have to change some fields in packet.
I can do it using pcap4j, but after packet modification I can only send it to the network, which results in two packets (original and modified)
I'd like to "catch" this packet, not only read, or drop the original one and send the modified.