Unlike many other courses at this university, we in CMSC420 believe that you should be free to talk at length about the project with each other. The algorithms you'll be writing to implement data structures are not secrets; in most cases you will have pseudocode or even actual code available to you through many resources. Piazza is mandatory reading in this course and is the perfect place to ask questions and get answers about the project, Java, the data structures, the meaning of life, etc.
Do note, however, that even though our policy is more lenient than other professors in their courses, we do take academic honesty quite seriously and students have received XFs in this course for blatantly copying other students' code. It's one thing to develop an algorithm with another student--it's another to copy and paste your buddy's code. We will still be doing the standard code comparisons not only between your code but also the code of students of semesters past (yes, we keep it). So don't try any funny stuff, and you'll be fine. The general rule of thumb: when in doubt, cite your resource via in-code comments and notify the professor and ask permission.