--- /dev/null	2014-02-02 21:38:48.000000000 +0800
+++ new/src/share/sample/stream/Tabulate.java	2014-02-02 21:38:48.000000000 +0800
@@ -0,0 +1,98 @@
+/*
+ * 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;
+
+import stream.data.Customer;
+import stream.data.Vendor;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import static java.util.stream.Collectors.*;
+import java.util.stream.Stream;
+
+/**
+ * A demo shows how does Stream's flatMap works. Demo shows tabulate stream
+ * element to single element stream or empty stream
+ *
+ * @author tyan
+ */
+public class Tabulate extends DemoHelper {
+    /**
+     * Join vendor and customer that in same country. note not all vendor
+     * has customer
+     * @return  a list of customer-vendor pair which in same country
+     */
+    public static Map<Customer, List<Vendor>> sameCountryCustomerAndVendors() {
+        Map<String, List<Vendor>> countryToVendors = vendors.stream().
+                // group vendors by their country
+                collect(groupingBy(Vendor::getCountry));
+        //Find customer in countryToVendors with key as customer's country
+        Function<Customer, List<Vendor>> vendorsInSameCustomerCountry
+                = customer-> countryToVendors.getOrDefault(
+                        customer.getCountry(), new ArrayList<>());
+        //Map customer to vendor who are same country as customer's
+        return customers.stream().
+                filter(c -> countryToVendors.containsKey(c.getCountry())).
+                collect(toMap(Function.identity(), vendorsInSameCustomerCountry));
+    }
+
+    /**
+     * flatMap can generate empty stream, sometimes it's helpful for ruling
+     * out data
+     * @return   a string set who is either customer and vendor both.
+     */
+    public static Set<String> bothCustomerAndVendor() {
+        Set<String> vendorsName = vendors.stream().
+                map(Vendor::getVendorName).
+                collect(toSet());
+        return customers.stream().
+                //map customer to its name
+                map(Customer::getCompanyName).
+                //query vendor set with customer's name, if exist, create
+                //a stream with single element customer name, if doesn't, create
+                //an empty stream
+                flatMap(c -> vendorsName.contains(c)
+                        ? Stream.of(c) : Stream.empty()).
+                //convert all match name into a set
+                collect(Collectors.toSet());
+    }
+}