refact: use new instanceof syntax

Author: bjansen

src/main/java/org/antlr/intellij/plugin/preview/HierarchyViewer.java

@@ -112,8 +112,7 @@ public void selectNodeAtOffset(int offset) {
 	private DefaultMutableTreeNode getNodeAtOffset(DefaultMutableTreeNode node, int offset) {
 		Tree tree = (Tree) node.getUserObject();
 
-		if ( tree instanceof ParserRuleContext ) {
-			ParserRuleContext ctx = (ParserRuleContext) tree;
+		if ( tree instanceof ParserRuleContext ctx ) {
 			if ( inBounds(ctx, offset) ) {
 				for ( int i = 0; i<node.getChildCount(); i++ ) {
 					DefaultMutableTreeNode child = (DefaultMutableTreeNode) node.getChildAt(i);
@@ -127,9 +126,7 @@ private DefaultMutableTreeNode getNodeAtOffset(DefaultMutableTreeNode node, int
 				return node;
 			}
 		}
-		else if ( tree instanceof TerminalNode ) {
-			TerminalNode terminal = (TerminalNode) tree;
-
+		else if ( tree instanceof TerminalNode terminal ) {
 			if ( terminal.getSymbol().getStartIndex()<=offset && terminal.getSymbol().getStopIndex()>=offset ) {
 				return node;
 			}