Adding maven wrapper to Dubbo project

.mvn/wrapper/maven-wrapper.properties

@@ -0,0 +1 @@
+distributionUrl=https://repo1.maven.org/maven2/org/apache/maven/apache-maven/3.5.0/apache-maven-3.5.0-bin.zip

.travis.yml

@@ -7,7 +7,7 @@ jdk:
     - openjdk7
 
 script:
-    - travis_wait 30 mvn clean package
+    - travis_wait 30 ./mvnw clean package
 
 after_success:
   - bash <(curl -s https://codecov.io/bash)

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

@@ -97,30 +97,37 @@ public final boolean weakCompareAndSet(int expect, int update) {
         return indexUpdater.weakCompareAndSet(this, expect, update);
     }
 
+    @Override
     public byte byteValue() {
         return (byte) get();
     }
 
+    @Override
     public short shortValue() {
         return (short) get();
     }
 
+    @Override
     public int intValue() {
         return get();
     }
 
+    @Override
     public long longValue() {
         return (long) get();
     }
 
+    @Override
     public float floatValue() {
         return (float) get();
     }
 
+    @Override
     public double doubleValue() {
         return (double) get();
     }
 
+    @Override
     public String toString() {
         return Integer.toString(get());
     }