StateMachine implementation for Java test code

gistfile1.java

  @Test
  public void testSimpleStateMachine() throws ExecutionException, InterruptedException {
    final StateMachine m = new StateMachine("first");
    m.on("first", new Handler<StringBuffer>() {
      @Override public void handle(StringBuffer sb) {
        sb.append("1");
        m.state("second", sb);
      }
    });
    m.on("second", new Handler<StringBuffer>() {
      @Override public void handle(StringBuffer sb) {
        sb.append("2");
        m.state("third", sb);
      }
    });
    m.on("third", new Handler<StringBuffer>() {
      @Override public void handle(StringBuffer sb) {
        sb.append("3");
        m.state(null, sb);
      }
    });
    Promise<StringBuffer> p = m.run(new StringBuffer());

    assertEquals("Buffer was properly mutated", "123", p.get().toString());
  }