In this paper we describe a constraint-based methodology for writing concurrent and distributed Java applications. A system is modeled as: (a) a set of Java threads containing a sequence of markers, denoting the threads points of interest; and (b) a constraint store. The key advantages are that there is a clear separation of the concurrency aspects of the system?s threads from the threads functionality, and threads are coordinated by a formal constraint-based specification. The treatment of the concurrency issues as orthogonal to the rest of the code allows programmers to independently develop one component from the other, and the declarative nature of the coordination mechanism provides a natural framework for formal verification, synthesis and transformation of concurrent Java programs.