fix bug of viewing enum obj (#3041)

Author: leizhiyuan

core/src/main/java/com/taobao/arthas/core/view/ObjectView.java

@@ -587,7 +587,7 @@ else if (Date.class.isInstance(obj)) {
                 appendStringBuilder(buf, format("@%s[%s]", className, new SimpleDateFormat("yyyy-MM-dd HH:mm:ss,SSS").format(obj)));
             }
 
-            else if (object instanceof Enum<?>) {
+            else if (obj instanceof Enum<?>) {
                 appendStringBuilder(buf, format("@%s[%s]", className, obj));
             }
 

core/src/test/java/com/taobao/arthas/core/view/ObjectViewTest.java

@@ -189,6 +189,23 @@ public void testThrowable() {
         Assert.assertTrue(objectView.draw().startsWith("java.lang.Exception: test"));
     }
 
+    @Test
+    public void testEnum() {
+        EnumDemo t = EnumDemo.DEMO;
+        ObjectView objectView = new ObjectView(t, 3);
+        Assert.assertEquals("@EnumDemo[DEMO]", objectView.draw());
+    }
+
+    @Test
+    public void testEnumList() {
+        EnumDemo t = EnumDemo.DEMO;
+        ObjectView objectView = new ObjectView(new Object[] {t}, 3);
+        String expected = "@Object[][\n" +
+            "    @EnumDemo[DEMO],\n" +
+            "]";
+        Assert.assertEquals(expected, objectView.draw());
+    }
+
     @Test
     public void testDate() {
         Date d = new Date(1531204354961L - TimeZone.getDefault().getRawOffset()
@@ -303,4 +320,8 @@ public void setJ(String j) {
             this.j = j;
         }
     }
+
+    public enum EnumDemo {
+        DEMO;
+    }
 }