Add an examples for distributed counters.

src/test/java/net/openhft/chronicle/map/example/DistributedSequenceMain.java

@@ -0,0 +1,29 @@
+package net.openhft.chronicle.map.example;
+
+import net.openhft.chronicle.map.ChronicleMap;
+import net.openhft.chronicle.map.ChronicleMapBuilder;
+import net.openhft.lang.model.DataValueClasses;
+import net.openhft.lang.values.LongValue;
+
+import java.io.File;
+import java.io.IOException;
+
+public class DistributedSequenceMain {
+
+    public static void main(String... ignored) throws IOException {
+        Class<LongValue> longValueClass = DataValueClasses.directClassFor(LongValue.class);
+        ChronicleMap<String, LongValue> map =
+                ChronicleMapBuilder.of(String.class, longValueClass)
+                        .entries(128)
+                        .actualSegments(1)
+                        .create(new File("/tmp/counters"));
+        LongValue value = DataValueClasses.newDirectReference(longValueClass);
+        map.acquireUsing("sequence", value);
+
+        for (int i = 0; i < 1000000; i++) {
+            long nextId = value.addAtomicValue(1);
+        }
+
+        map.close();
+    }
+}