GH-373 use default values if they cannot be obtained from heap dump

Author: thurka

visualvm/libs.profiler/lib.profiler.heap/src/org/graalvm/visualvm/lib/jfluid/heap/HprofProxy.java

@@ -147,6 +147,10 @@ private static int[] getStringUTF16ShiftBytes(Heap heap) {
         Integer HI_BYTE_SHIFT = (Integer) utf16Class.getValueOfStaticField("HI_BYTE_SHIFT");      // NOI18N
         Integer LO_BYTE_SHIFT = (Integer) utf16Class.getValueOfStaticField("LO_BYTE_SHIFT");      // NOI18N
 
-        return new int[] {HI_BYTE_SHIFT.intValue(),LO_BYTE_SHIFT.intValue()};
+        if (HI_BYTE_SHIFT != null && LO_BYTE_SHIFT != null) {
+            return new int[] {HI_BYTE_SHIFT.intValue(),LO_BYTE_SHIFT.intValue()};
+        }
+        // use default
+        return new int[] {0,8};
     }
 }

visualvm/libs.profiler/profiler.heapwalker/src/org/graalvm/visualvm/lib/profiler/heapwalk/details/api/StringDecoder.java

@@ -43,10 +43,13 @@ public StringDecoder(Heap heap, byte c, List<String> val) {
         coder = c;
         values = val;
         if (coder == 1) {
-            if (heap != null) {
-                JavaClass utf16Class = heap.getJavaClassByName("java.lang.StringUTF16"); // NOI18N
-                HI_BYTE_SHIFT = (Integer) utf16Class.getValueOfStaticField("HI_BYTE_SHIFT"); // NOI18N
-                LO_BYTE_SHIFT = (Integer) utf16Class.getValueOfStaticField("LO_BYTE_SHIFT"); // NOI18N
+            JavaClass utf16Class = heap.getJavaClassByName("java.lang.StringUTF16"); // NOI18N
+            Integer hiShift = (Integer) utf16Class.getValueOfStaticField("HI_BYTE_SHIFT"); // NOI18N
+            Integer loShift = (Integer) utf16Class.getValueOfStaticField("LO_BYTE_SHIFT"); // NOI18N
+
+            if (hiShift != null && loShift != null) {
+                HI_BYTE_SHIFT = hiShift.intValue();
+                LO_BYTE_SHIFT = loShift.intValue();
             } else {
                 // use default
                 HI_BYTE_SHIFT = 0;