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# Theta Sketch Java Example

    // simplified file operations and no error handling for clarity

    import java.io.FileInputStream;
    import java.io.FileOutputStream;

    import org.apache.datasketches.memory.Memory;
    import org.apache.datasketches.theta.Sketch;
    import org.apache.datasketches.theta.Sketches;
    import org.apache.datasketches.theta.UpdateSketch;
    import org.apache.datasketches.theta.Union;
    import org.apache.datasketches.theta.Intersection;
    import org.apache.datasketches.theta.SetOperation;

    // this section generates two sketches with some overlap
    // and serializes them into files in compact (not updatable) form
    {
      // 100000 unique keys
      UpdateSketch sketch1 = UpdateSketch.builder().build();
      for (int key = 0; key < 100000; key++) sketch1.update(key);
      FileOutputStream out1 = new FileOutputStream("ThetaSketch1.bin");
      out1.write(sketch1.compact().toByteArray());
      out1.close();

      // 100000 unique keys
      // the first 50000 unique keys overlap with sketch1
      UpdateSketch sketch2 = UpdateSketch.builder().build();
      for (int key = 50000; key < 150000; key++) sketch2.update(key);
      FileOutputStream out2 = new FileOutputStream("ThetaSketch2.bin");
      out2.write(sketch2.compact().toByteArray());
      out2.close();
    }

    // this section deserializes the sketches, produces union and intersection and prints the results
    {
      FileInputStream in1 = new FileInputStream("ThetaSketch1.bin");
      byte[] bytes1 = new byte[in1.available()];
      in1.read(bytes1);
      in1.close();
      Sketch sketch1 = Sketches.wrapSketch(Memory.wrap(bytes1));

      FileInputStream in2 = new FileInputStream("ThetaSketch2.bin");
      byte[] bytes2 = new byte[in2.available()];
      in2.read(bytes2);
      in2.close();
      Sketch sketch2 = Sketches.wrapSketch(Memory.wrap(bytes2));

      Union union = SetOperation.builder().buildUnion();
      union.union(sketch1);
      union.union(sketch2);
      Sketch unionResult = union.getResult();

      // debug summary of the union result sketch
      System.out.println(unionResult.toString());

      System.out.println("Union unique count estimate: " + unionResult.getEstimate());
      System.out.println("Union unique count lower bound 95% confidence: " + unionResult.getLowerBound(2));
      System.out.println("Union unique count upper bound 95% confidence: " + unionResult.getUpperBound(2));

      Intersection intersection = SetOperation.builder().buildIntersection();
      intersection.intersection(sketch1);
      intersection.intersection(sketch2);
      Sketch intersectionResult = intersection.getResult();

      // debug summary of the intersection result sketch
      System.out.println(intersectionResult.toString());

      System.out.println("Intersection unique count estimate: " + intersectionResult.getEstimate());
      System.out.println("Intersection unique count lower bound 95% confidence: " + intersectionResult.getLowerBound(2));
      System.out.println("Intersection unique count upper bound 95% confidence: " + intersectionResult.getUpperBound(2));
    }


    Output:
    ### HeapCompactOrderedSketch SUMMARY: 
       Estimate                : 149586.73149344584
       Upper Bound, 95% conf   : 154287.5017892762
       Lower Bound, 95% conf   : 145028.6046846571
       Theta (double)          : 0.027382107751846067
       Theta (long)            : 252555366948521403
       Theta (long) hex        : 038141c4a515c5bb
       EstMode?                : true
       Empty?                  : false
       Array Size Entries      : 4096
       Retained Entries        : 4096
       Seed Hash               : 93cc
    ### END SKETCH SUMMARY

    Union unique count estimate: 149586.73149344584
    Union unique count lower bound 95% confidence: 145028.6046846571
    Union unique count upper bound 95% confidence: 154287.5017892762

    ### HeapCompactOrderedSketch SUMMARY: 
       Estimate                : 48249.113729035394
       Upper Bound, 95% conf   : 50358.736970106176
       Lower Bound, 95% conf   : 46227.35737896924
       Theta (double)          : 0.04377282475820978
       Theta (long)            : 403733047849016500
       Theta (long) hex        : 059a591165205cb4
       EstMode?                : true
       Empty?                  : false
       Array Size Entries      : 2112
       Retained Entries        : 2112
       Seed Hash               : 93cc
    ### END SKETCH SUMMARY

    Intersection unique count estimate: 48249.113729035394
    Intersection unique count lower bound 95% confidence: 46227.35737896924
    Intersection unique count upper bound 95% confidence: 50358.736970106176