Unify context setting code (#231)

Author: zhengyu123

ddprof-lib/src/main/java/com/datadoghq/profiler/JavaProfiler.java

@@ -35,11 +35,9 @@
  */
 public final class JavaProfiler {
     static final Unsafe UNSAFE;
-    static final boolean isJDK8;
     static {
         Unsafe unsafe = null;
         String version = System.getProperty("java.version");
-        isJDK8 = version.startsWith("1.8");
         try {
             Field f = Unsafe.class.getDeclaredField("theUnsafe");
             f.setAccessible(true);
@@ -129,7 +127,7 @@ private void initializeContextStorage() {
         if (this.contextStorage == null) {
             int maxPages = getMaxContextPages0();
             if (maxPages > 0) {
-                if (isJDK8) {
+                if (UNSAFE != null) {
                     contextBaseOffsets = new long[maxPages];
                     // be sure to choose an illegal address as a sentinel value
                     Arrays.fill(contextBaseOffsets, Long.MIN_VALUE);
@@ -238,14 +236,14 @@ public void removeThread() {
      */
     public void setContext(long spanId, long rootSpanId) {
         int tid = TID.get();
-        if (isJDK8) {
-            setContextJDK8(tid, spanId, rootSpanId);
+        if (UNSAFE != null) {
+            setContextUnsafe(tid, spanId, rootSpanId);
         } else {
             setContextByteBuffer(tid, spanId, rootSpanId);
         }
     }
 
-    private void setContextJDK8(int tid, long spanId, long rootSpanId) {
+    private void setContextUnsafe(int tid, long spanId, long rootSpanId) {
         if (contextBaseOffsets == null) {
             return;
         }
@@ -313,14 +311,14 @@ public void clearContext() {
      */
     public void setContextValue(int offset, int value) {
         int tid = TID.get();
-        if (isJDK8) {
-            setContextJDK8(tid, offset, value);
+        if (UNSAFE != null) {
+            setContextUnsafe(tid, offset, value);
         } else {
             setContextByteBuffer(tid, offset, value);
         }
     }
 
-    private void setContextJDK8(int tid, int offset, int value) {
+    private void setContextUnsafe(int tid, int offset, int value) {
         if (contextBaseOffsets == null) {
             return;
         }
@@ -344,14 +342,14 @@ public void setContextByteBuffer(int tid, int offset, int value) {
 
     void copyTags(int[] snapshot) {
         int tid = TID.get();
-        if (isJDK8) {
-            copyTagsJDK8(tid, snapshot);
+        if (UNSAFE != null) {
+            copyTagsUnsafe(tid, snapshot);
         } else {
             copyTagsByteBuffer(tid, snapshot);
         }
     }
 
-    void copyTagsJDK8(int tid, int[] snapshot) {
+    void copyTagsUnsafe(int tid, int[] snapshot) {
         if (contextBaseOffsets == null) {
             return;
         }