Split.java

PCollection<String> names = ...;

PCollection<String> fooCollection = names.apply("FooTrans", ParDo.of(new DoFn<String, String>(){
  @ProcessElement
  public void processElement(ProcessContext c) {
    if(c.element().startsWith("Foo")){
      c.output(c.element());
    }
  }}));

PCollection<String> errCollection = names.apply("BarTrans", ParDo.of(new DoFn<String, String>(){
  @ProcessElement
  public void processElement(ProcessContext c) {
    if(c.element().startsWith("Bar")){
      c.output(c.element());
    }
  }
}));