Spark 2.9.1 incompattible types error

On compiling Spark 2.9.1 with OpenJDK 11.0.1, I run into an incompatible types error, shown below. I was able to get it to compile by making source code changes in line 147;
for (Enumeration e = node.children(); e.hasMoreElements(); ) {
changed to
for (Enumeration e = (Enumeration)(object) node.children();; ) { line 114;
//Enumeration nodeEnum = root.breadthFirstEnumeration();
changed to
Enumeration nodeEnum = (Enumeration)(object)root.depthFirstEnumeration(); line 136;
//Enumeration nodeEnum = children.elements();
changed to
Enumeration nodeEnum = (Enumeration)(object)children.elements();

This allows it to compile, but causes breaks when trying to use the conference browser tab.

Has anyone encountered this problem, and if so is there a solution?
below is my error log for reference

Yup, there’s a couple of these. Someone already provided a fix in

We’ll need to pick that apart, and apply things that are still relevant.