Merge pull request #348, AtomicPositiveInteger less memory used & provides better perf.

Author: fengjiachun

dubbo-common/src/main/java/com/alibaba/dubbo/common/utils/AtomicPositiveInteger.java

@@ -16,163 +16,120 @@
  */
 package com.alibaba.dubbo.common.utils;
 
-import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
 
-/**
- * AtomicPositiveInteger
- */
 public class AtomicPositiveInteger extends Number {
 
     private static final long serialVersionUID = -3038533876489105940L;
 
-    private final AtomicInteger i;
+    private static final AtomicIntegerFieldUpdater<AtomicPositiveInteger> indexUpdater =
+            AtomicIntegerFieldUpdater.newUpdater(AtomicPositiveInteger.class, "index");
+
+    @SuppressWarnings("unused")
+    private volatile int index = 0;
 
     public AtomicPositiveInteger() {
-        i = new AtomicInteger();
     }
 
     public AtomicPositiveInteger(int initialValue) {
-        i = new AtomicInteger(initialValue);
+        indexUpdater.set(this, initialValue);
     }
 
     public final int getAndIncrement() {
-        for (; ; ) {
-            int current = i.get();
-            int next = (current >= Integer.MAX_VALUE ? 0 : current + 1);
-            if (i.compareAndSet(current, next)) {
-                return current;
-            }
-        }
+        return indexUpdater.getAndIncrement(this) & Integer.MAX_VALUE;
     }
 
     public final int getAndDecrement() {
-        for (; ; ) {
-            int current = i.get();
-            int next = (current <= 0 ? Integer.MAX_VALUE : current - 1);
-            if (i.compareAndSet(current, next)) {
-                return current;
-            }
-        }
+        return indexUpdater.getAndDecrement(this) & Integer.MAX_VALUE;
     }
 
     public final int incrementAndGet() {
-        for (; ; ) {
-            int current = i.get();
-            int next = (current >= Integer.MAX_VALUE ? 0 : current + 1);
-            if (i.compareAndSet(current, next)) {
-                return next;
-            }
-        }
+        return indexUpdater.incrementAndGet(this) & Integer.MAX_VALUE;
     }
 
     public final int decrementAndGet() {
-        for (; ; ) {
-            int current = i.get();
-            int next = (current <= 0 ? Integer.MAX_VALUE : current - 1);
-            if (i.compareAndSet(current, next)) {
-                return next;
-            }
-        }
+        return indexUpdater.decrementAndGet(this) & Integer.MAX_VALUE;
     }
 
     public final int get() {
-        return i.get();
+        return indexUpdater.get(this) & Integer.MAX_VALUE;
     }
 
     public final void set(int newValue) {
         if (newValue < 0) {
             throw new IllegalArgumentException("new value " + newValue + " < 0");
         }
-        i.set(newValue);
+        indexUpdater.set(this, newValue);
     }
 
     public final int getAndSet(int newValue) {
         if (newValue < 0) {
             throw new IllegalArgumentException("new value " + newValue + " < 0");
         }
-        return i.getAndSet(newValue);
+        return indexUpdater.getAndSet(this, newValue) & Integer.MAX_VALUE;
     }
 
     public final int getAndAdd(int delta) {
         if (delta < 0) {
             throw new IllegalArgumentException("delta " + delta + " < 0");
         }
-        for (; ; ) {
-            int current = i.get();
-            int next = (current >= Integer.MAX_VALUE - delta + 1 ? delta - 1 : current + delta);
-            if (i.compareAndSet(current, next)) {
-                return current;
-            }
-        }
+        return indexUpdater.getAndAdd(this, delta) & Integer.MAX_VALUE;
     }
 
     public final int addAndGet(int delta) {
         if (delta < 0) {
             throw new IllegalArgumentException("delta " + delta + " < 0");
         }
-        for (; ; ) {
-            int current = i.get();
-            int next = (current >= Integer.MAX_VALUE - delta + 1 ? delta - 1 : current + delta);
-            if (i.compareAndSet(current, next)) {
-                return next;
-            }
-        }
+        return indexUpdater.addAndGet(this, delta) & Integer.MAX_VALUE;
     }
 
     public final boolean compareAndSet(int expect, int update) {
         if (update < 0) {
             throw new IllegalArgumentException("update value " + update + " < 0");
         }
-        return i.compareAndSet(expect, update);
+        return indexUpdater.compareAndSet(this, expect, update);
     }
 
     public final boolean weakCompareAndSet(int expect, int update) {
         if (update < 0) {
             throw new IllegalArgumentException("update value " + update + " < 0");
         }
-        return i.weakCompareAndSet(expect, update);
+        return indexUpdater.weakCompareAndSet(this, expect, update);
     }
 
-    @Override
     public byte byteValue() {
-        return i.byteValue();
+        return (byte) get();
     }
 
-    @Override
     public short shortValue() {
-        return i.shortValue();
+        return (short) get();
     }
 
-    @Override
     public int intValue() {
-        return i.intValue();
+        return get();
     }
 
-    @Override
     public long longValue() {
-        return i.longValue();
+        return (long) get();
     }
 
-    @Override
     public float floatValue() {
-        return i.floatValue();
+        return (float) get();
     }
 
-    @Override
     public double doubleValue() {
-        return i.doubleValue();
+        return (double) get();
     }
 
-    @Override
     public String toString() {
-        return i.toString();
+        return Integer.toString(get());
     }
 
     @Override
     public int hashCode() {
         final int prime = 31;
         int result = 1;
-        result = prime * result + i.hashCode();
+        result = prime * result + get();
         return result;
     }
 
@@ -181,7 +138,6 @@ public boolean equals(Object obj) {
         if (this == obj) return true;
         if (!(obj instanceof AtomicPositiveInteger)) return false;
         AtomicPositiveInteger other = (AtomicPositiveInteger) obj;
-        return i.intValue() == other.i.intValue();
+        return intValue() == other.intValue();
     }
-
-}
+}