[java] CloseResource false-positive with URLClassLoader in cast expression

[adangel]

That one could be considered a FP, since we don't create the URLClassLoader here. We just cast the method argument, which is a ClassLoader, to a local variable, which is a URLClassLoader and therefore AutoCloseable...

_Originally posted by @adangel in #1955 _

Code example:

pmd/pmd-core/src/main/java/net/sourceforge/pmd/cache/AbstractAnalysisCache.java

Lines 117 to 127 in 5156e89

	public void checkValidity(final RuleSets ruleSets, final ClassLoader auxclassPathClassLoader) {
	boolean cacheIsValid = cacheExists();
	if (cacheIsValid && ruleSets.getChecksum() != rulesetChecksum) {
	LOG.info("Analysis cache invalidated, rulesets changed.");
	cacheIsValid = false;
	}
	final long currentAuxClassPathChecksum;
	if (auxclassPathClassLoader instanceof URLClassLoader) {
	final URLClassLoader urlClassLoader = (URLClassLoader) auxclassPathClassLoader;

The variable "urlClassLoader" is not closed in this method and this is detected by the rule.
However, since the URLClassLoader is not created within this method, it should be ignored.