add q-digest data structure

pom.xml

@@ -62,6 +62,10 @@
             <artifactId>jgraphx</artifactId>
             <version>1.10.1.3</version>
         </dependency>
-
+        <dependency>
+            <groupId>it.unimi.dsi</groupId>
+            <artifactId>fastutil</artifactId>
+            <version>7.0.12</version>
+        </dependency>
     </dependencies>
 </project>
\ No newline at end of file

src/main/java/fucoin/wallet/WalletImpl.java

@@ -21,6 +21,9 @@ import java.util.concurrent.ConcurrentLinkedQueue;
 
 public class WalletImpl extends AbstractWallet {
 
+    private static final double sCompression = 0.7;
+    private QDigest qDigest = new QDigest(sCompression);
+
     private ActorRef preKnownNeighbour;
     private ActorRef remoteSuperVisorActor;
     private transient WalletGuiControl gui;
@@ -51,6 +54,7 @@ public class WalletImpl extends AbstractWallet {
      */
     public void addAmount(int amount) {
         setAmount(this.getAmount() + amount);
+        qDigest.offer(amount);
         addLogMsg(" My amount is now " + this.getAmount());
     }