--- /dev/null 2014-02-02 21:38:56.000000000 +0800
+++ new/src/share/sample/stream/parallel/MonteCarloPI.java 2014-02-02 21:38:55.000000000 +0800
@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2013 Oracle and/or its affiliates. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of Oracle nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * This source code is provided to illustrate the usage of a given feature
+ * or technique and has been deliberately simplified. Additional steps
+ * required for a production-quality application, such as security checks,
+ * input validation and proper error handling, might not be present in
+ * this sample code.
+ */
+package stream.parallel;
+
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.stream.LongStream;
+
+/**
+ * This demo shows how to use the parallel mode and the Monte Carlo method to
+ * calculate the value of PI
+ *
+ * @author tyan
+ */
+public class MonteCarloPI {
+
+ public static void main(String[] args) {
+ System.out.println("This might take several minutes, "
+ + "depending on your system");
+ LongStream.iterate(10l, l -> 10 * l).
+ limit(10).
+ forEach(times -> {
+ System.out.printf(
+ "The value of PI is %1.14f after %,d times calculation\n",
+ pi(times), times);
+ });
+ }
+
+ /**
+ * Use the Monte Carlo method to calculate the value of PI. basic algorithm
+ * is: 1. Draw a square on the ground, then inscribe a circle within it. 2.
+ * Scatter some objects of uniform size (grains of rice or sand) over the
+ * square. 3. Count the total number of objects inside the circle and the
+ * total number of objects overall. 4. The ratio of the two total is an
+ * estimate of the ratio of the two areas, which is PI/4. Multiply the
+ * result by 4 to estimate PI.
+ *
+ * @param x how many times randomly selected a point
+ * @return value of π by x times calculation
+ */
+ private static double pi(long N) {
+ long M = LongStream.range(0, N).parallel().filter(sr -> {
+ // Random picked up point to check if it's in the circle.
+ double x = ThreadLocalRandom.current().nextDouble(-1, 1);
+ double y = ThreadLocalRandom.current().nextDouble(-1, 1);
+
+ return x * x + y * y < 1.0 * 1.0; // Not using
+ }).count();
+ return 4.0 * M / N;
+ }
+
+ /**
+ * Use ThreadLocalRandom to simulate that whether a point is inside the
+ * circle or outside the circle
+ *
+ * @return 1 randomly selected point is inside the circle 0 randomly
+ * selected point is outside the circle
+ */
+ private static long hit() {
+ ThreadLocalRandom lr = ThreadLocalRandom.current();
+ double x = lr.nextDouble(1.0);
+ double y = lr.nextDouble(1.0);
+ return Math.sqrt(y * y + x * x) <= 1.0 ? 1 : 0;
+ }
+}