title: Getting List From PCollections
body: <p>I want a list values from Pcollection.</p>
  
  <pre><code>PCollection&lt;List&lt;Integer&gt;&gt; lst =    bqT2.apply(ParDo.of(new 
  UserId()));  // line 1
  List myList = lst.getAll(); // line 2 
  </code></pre>
  
  <p>but there is no "getAll()" function</p>
  
  <p>I found something similar </p>
  
  <pre><code>    List&lt;String&gt; dummylist = Arrays.asList(dummy);
      DoFnTester&lt;String,String&gt; fnTester = DoFnTester.of(new AAA(mapview));
      fnTester.setSideInputInGlobalWindow(mapview, csvlist);
      //dummylines.apply(ParDo.of(fnTester));
      List&lt;String&gt; results = fnTester.processBatch(dummylist);
  </code></pre>
  
  <p>but I didn't found any way to use "DoFnTester" function for getting list items.</p>
  
  <p>Is there any way to list from PCollection?</p>
  
  <p>Just to elaborate more I have two PCollections.</p>
  
  <pre><code>PCollection   p1 = pipeline.apply("",
  BigQueryIO.read().fromQuery("SELECT * from myTable where userid in " +  lst + ));
  </code></pre>
  
  <p>Note: lst is from line 1</p>
  
  <p>Not sure if google dataflow doesn't support simple usecases.</p>