bug fixed & optimzed Histogram memory used

src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java

@@ -1388,7 +1388,7 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
         map.put("ResultSetLastErrorStackTrace", null);
 
         // 35 - 39
-        map.put("ConnectionConnectCount", createErrorCount);
+        map.put("ConnectionConnectCount", this.getConnectCount());
         if (createError != null) {
             map.put("ConnectionErrorLastMessage", createError.getMessage());
             map.put("ConnectionErrorLastStackTrace", IOUtils.getStackTrace(createError));

src/main/java/com/alibaba/druid/util/Histogram.java

@@ -16,28 +16,25 @@
 package com.alibaba.druid.util;
 
 import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.AtomicLongArray;
 
 public class Histogram {
 
-    private final long[]       ranges;
-    private final AtomicLong[] rangeCounters;
+    private final long[]          ranges;
+    private final AtomicLongArray rangeCounters;
 
     public Histogram(long... ranges){
         this.ranges = ranges;
-        this.rangeCounters = new AtomicLong[ranges.length + 1];
-        for (int i = 0; i < rangeCounters.length; i++) {
-            rangeCounters[i] = new AtomicLong();
-        }
+        this.rangeCounters = new AtomicLongArray(ranges.length + 1);
     }
-    
+
     public static Histogram makeHistogram(int rangeCount) {
         long[] rangeValues = new long[rangeCount];
-        
+
         for (int i = 0; i < rangeValues.length; ++i) {
             rangeValues[i] = (long) Math.pow(10, i);
         }
-        
+
         return new Histogram(rangeValues);
     }
 
@@ -47,20 +44,17 @@ public class Histogram {
             this.ranges[i] = TimeUnit.MILLISECONDS.convert(ranges[i], timeUnit);
         }
 
-        rangeCounters = new AtomicLong[ranges.length + 1];
-        for (int i = 0; i < rangeCounters.length; ++i) {
-            rangeCounters[i] = new AtomicLong();
-        }
+        rangeCounters = new AtomicLongArray(ranges.length + 1);
     }
 
     public void reset() {
-        for (int i = 0; i < rangeCounters.length; i++) {
-            rangeCounters[i].set(0);
+        for (int i = 0; i < rangeCounters.length(); i++) {
+            rangeCounters.set(i, 0);
         }
     }
 
     public void record(long millis) {
-        int index = rangeCounters.length - 1;
+        int index = rangeCounters.length() - 1;
         for (int i = 0; i < ranges.length; ++i) {
             if (millis < ranges[i]) {
                 index = i;
@@ -68,17 +62,17 @@ public class Histogram {
             }
         }
 
-        rangeCounters[index].incrementAndGet();
+        rangeCounters.incrementAndGet(index);
     }
 
     public long get(int index) {
-        return rangeCounters[index].get();
+        return rangeCounters.get(index);
     }
 
     public long[] toArray() {
-        long[] array = new long[rangeCounters.length];
-        for (int i = 0; i < rangeCounters.length; i++) {
-            array[i] = rangeCounters[i].get();
+        long[] array = new long[rangeCounters.length()];
+        for (int i = 0; i < rangeCounters.length(); i++) {
+            array[i] = rangeCounters.get(i);
         }
         return array;
     }
@@ -86,29 +80,29 @@ public class Histogram {
     public long[] getRanges() {
         return ranges;
     }
-    
+
     public long getValue(int index) {
-        return rangeCounters[index].get();
+        return rangeCounters.get(index);
     }
-    
+
     public long getSum() {
         long sum = 0;
-        for (int i = 0; i < rangeCounters.length; ++i) {
-            sum += rangeCounters[i].get();
+        for (int i = 0; i < rangeCounters.length(); ++i) {
+            sum += rangeCounters.get(i);
         }
         return sum;
     }
-    
+
     public String toString() {
-    	StringBuilder buf = new StringBuilder();
-    	buf.append('[');
-    	for (int i = 0; i < rangeCounters.length; ++i) {
-    		if (i != 0) {
-    			buf.append(',');
-    		}
-    		buf.append(rangeCounters[i].get());
-    	}
-    	buf.append(']');
-    	return buf.toString();
+        StringBuilder buf = new StringBuilder();
+        buf.append('[');
+        for (int i = 0; i < rangeCounters.length(); ++i) {
+            if (i != 0) {
+                buf.append(',');
+            }
+            buf.append(rangeCounters.get(i));
+        }
+        buf.append(']');
+        return buf.toString();
     }
 }

src/test/java/com/alibaba/druid/stat/HistogramMemoryTest.java

@@ -0,0 +1,26 @@
+package com.alibaba.druid.stat;
+
+import java.lang.management.ManagementFactory;
+import java.text.NumberFormat;
+
+import com.alibaba.druid.util.Histogram;
+
+import junit.framework.TestCase;
+
+public class HistogramMemoryTest extends TestCase {
+
+    public void test_0() throws Exception {
+        long memoryStart = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed();
+        
+        final int COUNT = 1024 * 1;
+        Object[] items = new Object[COUNT];
+        for (int i = 0; i < COUNT; ++i) {
+            // items[i] = new JdbcSqlStat("");
+            items[i] = Histogram.makeHistogram(20);
+        }
+        
+        long memoryEnd = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed();
+        
+        System.out.println("memory used : " + NumberFormat.getInstance().format(memoryEnd - memoryStart));
+    }
+}