Adding stat data

BUILD

@@ -31,7 +31,8 @@ java_library(
   srcs = glob([
     "src/RateLimit.java", 
     "src/PeriodicThread.java",
-    "src/WeightedRandomSelector.java"]),
+    "src/WeightedRandomSelector.java",
+    "src/StatData.java"]),
   deps = [
   ],
 )

src/RateLimit.java

@@ -55,3 +55,4 @@ public synchronized boolean waitForRate(double bytes)
 
 
 }
+

src/StatData.java

@@ -0,0 +1,111 @@
+package duckutil;
+
+import java.text.DecimalFormat;
+
+public class StatData
+{
+
+    private long num=0;
+    private long sum_x=0;
+    private long sum_x_2=0;
+    private long min=1000000000;
+    private long max=0;
+
+    public StatData()
+    {
+
+    }
+
+    public StatData(long num, long sum_x, long sum_x_2, long min, long max)
+    {
+        this.num = num;
+        this.sum_x = sum_x;
+        this.sum_x_2 = sum_x_2;
+        this.min = min;
+        this.max = max;
+    }
+
+    public synchronized void addDataPoint(long x)
+    {
+        num++;
+        sum_x += x;
+        sum_x_2 += x*x;
+
+        min = Math.min(min, x);
+        max = Math.max(max, x);
+
+    }
+
+
+  public synchronized void addAllPoints(StatData o)
+  {
+    num += o.num;
+    sum_x += o.sum_x;
+    sum_x_2 += o.sum_x_2;
+
+    min = Math.min(min, o.min);
+    max = Math.max(max, o.max);
+
+  }
+
+    /**
+     * Return duplicate StatData and reset this one
+     */
+    public synchronized StatData copyAndReset()
+    {
+        StatData n = new StatData(num, sum_x, sum_x_2, min, max);
+
+        num = 0;
+        sum_x = 0;
+        sum_x_2 = 0;
+        min = 1000000000;
+        max = 0;
+
+        return n;
+
+    }
+
+    public synchronized double getMean()
+    {
+        if (num ==0) return 0.0;
+        return (double)sum_x / (double) num;
+    }
+
+    public synchronized double getStdDev()
+    {
+        if (num == 0) return 0.0;
+
+        double e_x = sum_x / num;
+        double e_x_2 = sum_x_2 / num;
+
+        return Math.sqrt(e_x_2 - e_x * e_x);
+    }
+
+    public synchronized long getMin(){return min;}
+    public synchronized long getMax(){return max;}
+    public synchronized long getNum(){return num;}
+
+
+    public synchronized void print(String label, DecimalFormat df)
+    {
+
+        System.out.println(getReport(label,df));
+    }
+
+    public synchronized String getReport(String label, DecimalFormat df)
+    {
+        StringBuilder sb= new StringBuilder();
+
+        sb.append(label);
+        sb.append(" n: " + df.format(num));
+        sb.append(" min: " + df.format(min));
+        sb.append(" avg: " + df.format(getMean()));
+        sb.append(" max: " + df.format(max));
+        sb.append(" stddev: " + df.format(getStdDev()));
+
+
+        return sb.toString();
+
+    }
+
+}