Code refinement for JDK-picked classes (#1014)

sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/statistic/base/LongAdder.java

@@ -46,6 +46,7 @@ public class LongAdder extends Striped64 implements Serializable {
     /**
      * Version of plus for use in retryUpdate
      */
+    @Override
     final long fn(long v, long x) { return v + x; }
 
     /**
@@ -153,6 +154,7 @@ public class LongAdder extends Striped64 implements Serializable {
      *
      * @return the String representation of the {@link #sum}
      */
+    @Override
     public String toString() {
         return Long.toString(sum());
     }
@@ -162,6 +164,7 @@ public class LongAdder extends Striped64 implements Serializable {
      *
      * @return the sum
      */
+    @Override
     public long longValue() {
         return sum();
     }
@@ -170,6 +173,7 @@ public class LongAdder extends Striped64 implements Serializable {
      * Returns the {@link #sum} as an {@code int} after a narrowing
      * primitive conversion.
      */
+    @Override
     public int intValue() {
         return (int)sum();
     }
@@ -178,6 +182,7 @@ public class LongAdder extends Striped64 implements Serializable {
      * Returns the {@link #sum} as a {@code float}
      * after a widening primitive conversion.
      */
+    @Override
     public float floatValue() {
         return (float)sum();
     }
@@ -186,6 +191,7 @@ public class LongAdder extends Striped64 implements Serializable {
      * Returns the {@link #sum} as a {@code double} after a widening
      * primitive conversion.
      */
+    @Override
     public double doubleValue() {
         return (double)sum();
     }

sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/statistic/base/Striped64.java

@@ -136,6 +136,7 @@ abstract class Striped64 extends Number {
      * The corresponding ThreadLocal class
      */
     static final class ThreadHashCode extends ThreadLocal<HashCode> {
+        @Override
         public HashCode initialValue() { return new HashCode(); }
     }
 
@@ -330,6 +331,7 @@ abstract class Striped64 extends Number {
                 return java.security.AccessController.doPrivileged
                     (new java.security
                         .PrivilegedExceptionAction<sun.misc.Unsafe>() {
+                        @Override
                         public sun.misc.Unsafe run() throws Exception {
                             java.lang.reflect.Field f = sun.misc
                                 .Unsafe.class.getDeclaredField("theUnsafe");