Update code checks both non-null and instance of a class in jdk.hotspot.agent module classes.
The checks and explicit casts could also be replaced with pattern matching for the instanceof operator.
For example:
    The following code:
              Object node = tree.getLastSelectedPathComponent();
              if (node != null && node instanceof SimpleTreeNode) {
                showInspector((SimpleTreeNode)node);
              }
    Can be simplified to:
              Object node = tree.getLastSelectedPathComponent();
              if (node instanceof SimpleTreeNode simpleNode) {
                showInspector(simpleNode);
              }