diff --git a/src/java/org/apache/poi/poifs/filesystem/POIFSDocument.java b/src/java/org/apache/poi/poifs/filesystem/POIFSDocument.java
index e43029d459..05881561b1 100644
--- a/src/java/org/apache/poi/poifs/filesystem/POIFSDocument.java
+++ b/src/java/org/apache/poi/poifs/filesystem/POIFSDocument.java
@@ -17,7 +17,7 @@
 
 package org.apache.poi.poifs.filesystem;
 
-import static java.util.Collections.emptyList;
+import static java.util.Collections.emptyIterator;
 
 import java.io.BufferedInputStream;
 import java.io.IOException;
@@ -235,7 +235,7 @@ public final class POIFSDocument implements POIFSViewable, Iterable<ByteBuffer>
     *		 store
     */
    public Iterator<Object> getViewableIterator() {
-      return emptyList().iterator();
+      return emptyIterator();
    }
 
    /**
diff --git a/src/java/org/apache/poi/poifs/filesystem/POIFSFileSystem.java b/src/java/org/apache/poi/poifs/filesystem/POIFSFileSystem.java
index 12e408ee63..23d9b3e2b0 100644
--- a/src/java/org/apache/poi/poifs/filesystem/POIFSFileSystem.java
+++ b/src/java/org/apache/poi/poifs/filesystem/POIFSFileSystem.java
@@ -858,7 +858,7 @@ public class POIFSFileSystem extends BlockStore
             return getRoot().getViewableIterator();
         }
 
-        return Collections.emptyList().iterator();
+        return Collections.emptyIterator();
     }
 
     /**
diff --git a/src/java/org/apache/poi/poifs/property/Property.java b/src/java/org/apache/poi/poifs/property/Property.java
index 59727a3584..a994ff133b 100644
--- a/src/java/org/apache/poi/poifs/property/Property.java
+++ b/src/java/org/apache/poi/poifs/property/Property.java
@@ -500,7 +500,7 @@ public abstract class Property implements Child, POIFSViewable {
      */
     public Iterator<Object> getViewableIterator()
     {
-        return Collections.emptyList().iterator();
+        return Collections.emptyIterator();
     }
 
     /**
diff --git a/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentTypeManager.java b/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentTypeManager.java
index 4ca6189955..5b356843c8 100644
--- a/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentTypeManager.java
+++ b/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentTypeManager.java
@@ -286,8 +286,8 @@ public abstract class ContentTypeManager {
             throw new IllegalArgumentException("contentType");
         }
 
-        return (this.defaultContentType.values().contains(contentType) || (this.overrideContentType != null && this.overrideContentType
-                .values().contains(contentType)));
+        return (this.defaultContentType.containsValue(contentType) || 
+                (this.overrideContentType != null && this.overrideContentType.containsValue(contentType)));
     }
 
     /**