From 585963930e4547159189e2dcf5a4c1233999a7eb Mon Sep 17 00:00:00 2001
From: Suzanne Millstein <smillst@cs.washington.edu>
Date: Thu, 16 Dec 2021 10:03:14 -0800
Subject: [PATCH] Fix issue 4987.

---
 .../org/checkerframework/framework/util/CheckerMain.java    | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/framework/src/main/java/org/checkerframework/framework/util/CheckerMain.java b/framework/src/main/java/org/checkerframework/framework/util/CheckerMain.java
index d2f850257bf..883ca5d5431 100644
--- a/framework/src/main/java/org/checkerframework/framework/util/CheckerMain.java
+++ b/framework/src/main/java/org/checkerframework/framework/util/CheckerMain.java
@@ -537,7 +537,11 @@ private List<String> expandWildcards(String pathElement) {
    */
   private List<String> jarFiles(String directory) {
     File dir = new File(directory);
-    return Arrays.asList(dir.list((d, name) -> name.endsWith(".jar") || name.endsWith(".JAR")));
+    String[] jarFiles = dir.list((d, name) -> name.endsWith(".jar") || name.endsWith(".JAR"));
+    if (jarFiles == null) {
+      return Collections.emptyList();
+    }
+    return Arrays.asList(jarFiles);
   }
 
   /** Invoke the compiler with all relevant jars on its classpath and/or bootclasspath. */