Update src/main/java/org/spdx/utility/DownloadCache.java

Only construct new `ReentrantLock` if needed.

Co-authored-by: Gary O'Neall <gary@sourceauditor.com>
Signed-off-by: Peter Monks <pmonks@gmail.com>

Author: pmonks

src/main/java/org/spdx/utility/DownloadCache.java

@@ -219,7 +219,7 @@ public InputStream getUrlInputStream(final URL url, final boolean restrictRedire
             if (cacheEnabled) {
                 // Per-URL critical section (to prevent cache stampede)
                 final String normalizedUrl = normalizeURL(url);
-                perUrlLocks.putIfAbsent(normalizedUrl, new ReentrantLock());
+                perUrlLocks.computeIfAbsent(normalizedUrl, k -> new ReentrantLock());
                 final Lock lock = perUrlLocks.get(normalizedUrl);
                 lock.lock();