This paper presents the XJava compiler for parallel programs. It exploits parallelism based on an object-oriented stream programming paradigm. XJava extends Java with new parallel constructs that do not expose programmers to low-level details of parallel programming on shared memory machines. Tasks define composable parallel activities, and new operators allow an easier expression of parallel patterns, such as pipelines, divide and conquer, or master/worker. We also present an automatic run-time mechanism that extends our previous work to automatically map tasks and parallel statements to threads.