diff --git a/jar-infer/jar-infer-lib/src/main/java/com/uber/nullaway/jarinfer/BytecodeAnnotator.java b/jar-infer/jar-infer-lib/src/main/java/com/uber/nullaway/jarinfer/BytecodeAnnotator.java
index c0ef25eab7..b657593e87 100644
--- a/jar-infer/jar-infer-lib/src/main/java/com/uber/nullaway/jarinfer/BytecodeAnnotator.java
+++ b/jar-infer/jar-infer-lib/src/main/java/com/uber/nullaway/jarinfer/BytecodeAnnotator.java
@@ -278,6 +278,8 @@ public static void annotateBytecodeInJar(
     // Do not use JarInputStream in place of JarFile/JarEntry. JarInputStream misses MANIFEST.MF
     // while iterating over the entries in the stream.
     // Reference: https://bugs.openjdk.java.net/browse/JDK-8215788
+    // Note: we can't just put the code below inside stream().forach(), because it can throw
+    // IOException.
     for (JarEntry jarEntry : inputJar.stream().collect(ImmutableList.toImmutableList())) {
       InputStream is = inputJar.getInputStream(jarEntry);
       copyAndAnnotateJarEntry(
diff --git a/jar-infer/jar-infer-lib/src/test/java/com/uber/nullaway/jarinfer/EntriesComparator.java b/jar-infer/jar-infer-lib/src/test/java/com/uber/nullaway/jarinfer/EntriesComparator.java
index 6660f5f639..267c073b03 100644
--- a/jar-infer/jar-infer-lib/src/test/java/com/uber/nullaway/jarinfer/EntriesComparator.java
+++ b/jar-infer/jar-infer-lib/src/test/java/com/uber/nullaway/jarinfer/EntriesComparator.java
@@ -16,6 +16,7 @@
 package com.uber.nullaway.jarinfer;
 
 import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableSet;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
@@ -43,11 +44,11 @@ public static boolean compareEntriesInJars(String jarFile1, String jarFile2) thr
     Preconditions.checkArgument(jarFile1.endsWith(".jar"), "invalid jar file: " + jarFile1);
     Preconditions.checkArgument(jarFile2.endsWith(".jar"), "invalid jar file: " + jarFile2);
     JarFile jar1 = new JarFile(jarFile1);
-    Set<String> jar1Entries = new HashSet<>();
-    jar1.stream().forEach(entry -> jar1Entries.add(entry.getName()));
     JarFile jar2 = new JarFile(jarFile2);
-    Set<String> jar2Entries = new HashSet<>();
-    jar2.stream().forEach(entry -> jar2Entries.add(entry.getName()));
+    Set<String> jar1Entries =
+        jar1.stream().map(ZipEntry::getName).collect(ImmutableSet.toImmutableSet());
+    Set<String> jar2Entries =
+        jar2.stream().map(ZipEntry::getName).collect(ImmutableSet.toImmutableSet());
     return jar1Entries.equals(jar2Entries);
   }
 
@@ -65,11 +66,11 @@ public static boolean compareEntriesInAars(String aarFile1, String aarFile2) thr
     Preconditions.checkArgument(aarFile1.endsWith(".aar"), "invalid aar file: " + aarFile1);
     Preconditions.checkArgument(aarFile2.endsWith(".aar"), "invalid aar file: " + aarFile2);
     ZipFile zip1 = new ZipFile(aarFile1);
-    Set<String> zip1Entries = new HashSet<>();
-    zip1.stream().forEach(entry -> zip1Entries.add(entry.getName()));
     ZipFile zip2 = new ZipFile(aarFile2);
-    Set<String> zip2Entries = new HashSet<>();
-    zip2.stream().forEach(entry -> zip2Entries.add(entry.getName()));
+    Set<String> zip1Entries =
+        zip1.stream().map(ZipEntry::getName).collect(ImmutableSet.toImmutableSet());
+    Set<String> zip2Entries =
+        zip2.stream().map(ZipEntry::getName).collect(ImmutableSet.toImmutableSet());
     if (!zip1Entries.equals(zip2Entries)) {
       return false;
     }