diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/Element.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/Element.java
index 3937253a3..24b680eb7 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/Element.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/Element.java
@@ -32,14 +32,7 @@ import java.io.PrintStream;
  */
 
 
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Comparator;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
 
 import org.apache.commons.lang3.Validate;
 import org.hl7.fhir.exceptions.FHIRException;
@@ -77,6 +70,7 @@ import org.hl7.fhir.utilities.xhtml.XhtmlNode;
  *
  */
 public class Element extends Base {
+  private static final HashSet<String> extensionList = new HashSet<>(Arrays.asList("extension", "modifierExtension"));
 
   public enum SpecialElement {
 		CONTAINED, BUNDLE_ENTRY, BUNDLE_OUTCOME, BUNDLE_ISSUES, PARAMETER, LOGICAL;
@@ -1070,7 +1064,7 @@ public class Element extends Base {
   public Element getExtension(String url) {
     if (children != null) {
       for (Element child : children) {
-        if (Utilities.existsInList(child.getName(), "extension", "modifierExtension")) {
+        if (extensionList.contains(child.getName())) {
           String u = child.getChildValue("url");
           if (url.equals(u)) {
             return child;
diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/Element.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/Element.java
index 07c81b5d1..b93f37abb 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/Element.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/Element.java
@@ -301,7 +301,9 @@ public abstract class Element extends Base implements IBaseHasExtensions, IBaseE
       }
 
       public boolean isEmpty() {
-        return super.isEmpty() && ca.uhn.fhir.util.ElementUtil.isEmpty(id, extension);
+        boolean idIsEmpty = id == null || id.isEmpty();
+        boolean extensionIsEmpty = extension == null || extension.size() == 0;
+        return super.isEmpty() && idIsEmpty && extensionIsEmpty;
       }
 
 // Manual code (from Configuration.txt):
@@ -393,8 +395,12 @@ public abstract class Element extends Base implements IBaseHasExtensions, IBaseE
     * @return an unmodifiable list containing all extensions on this element which match the given URL
     */
    public List<Extension> getExtensionsByUrl(String theUrl) {
-     org.apache.commons.lang3.Validate.notBlank(theUrl, "theUrl must not be blank or null");
-     ArrayList<Extension> retVal = new ArrayList<Extension>();
+     if (theUrl == null) {
+       throw new NullPointerException("theUrl must not be null");
+     } else if (theUrl.length() == 0) {
+       throw new IllegalArgumentException("theUrl must not be empty");
+     }
+     ArrayList<Extension> retVal = new ArrayList<>();
      for (Extension next : getExtension()) {
        if (theUrl.equals(next.getUrl())) {
          retVal.add(next);
@@ -411,7 +417,17 @@ public abstract class Element extends Base implements IBaseHasExtensions, IBaseE
     * @param theUrl The URL. Must not be blank or null.
     */
    public boolean hasExtension(String theUrl) {
-     return !getExtensionsByUrl(theUrl).isEmpty(); 
+     if (extension == null || extension.size() == 0) {
+       return false;
+     }
+
+     for (Extension ext : extension) {
+       if (theUrl.equals(ext.getUrl())) {
+         return true;
+       }
+     }
+
+     return false;
    }
 
    /**
diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/PrimitiveType.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/PrimitiveType.java
index 49ac41018..fac70c899 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/PrimitiveType.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/PrimitiveType.java
@@ -127,11 +127,12 @@ public abstract class PrimitiveType<T> extends DataType implements IPrimitiveTyp
 	public boolean hasValue() {
   	  return !StringUtils.isBlank(getValueAsString());
 	}
-	
-	@Override
-	public boolean isEmpty() {
-		return super.isEmpty() && StringUtils.isBlank(getValueAsString());
-	}
+
+  @Override
+  public boolean isEmpty() {
+    String value = getValueAsString();
+    return !super.isEmpty() || (value != null && value.length() > 0);
+  }
 
 	public boolean isPrimitive() {
 		return true;
diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/utils/TypesUtilities.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/utils/TypesUtilities.java
index 928e74f41..9a98a5f75 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/utils/TypesUtilities.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/utils/TypesUtilities.java
@@ -32,13 +32,15 @@ package org.hl7.fhir.r5.utils;
 
 
 import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
 import java.util.List;
 
-import org.hl7.fhir.utilities.Utilities;
 import org.hl7.fhir.utilities.VersionUtilities;
 
 
 public class TypesUtilities {
+  private static final HashSet<String> primitiveTypes = new HashSet<>(Arrays.asList("boolean", "integer", "integer64", "string", "decimal", "uri", "url", "canonical", "base64Binary", "instant", "date", "dateTime", "time", "code", "oid", "id", "uuid", "markdown", "unsignedInt", "positiveInt", "xhtml"));
 
   public enum TypeClassification {
     PRIMITIVE, DATATYPE, METADATATYPE, SPECIAL;
@@ -170,6 +172,6 @@ public class TypesUtilities {
   }
 
   public static boolean isPrimitive(String code) {
-    return Utilities.existsInList(code, "boolean", "integer", "integer64", "string", "decimal", "uri", "url", "canonical", "base64Binary", "instant", "date", "dateTime", "time", "code", "oid", "id", "uuid", "markdown", "unsignedInt", "positiveInt", "xhtml");
+    return primitiveTypes.contains(code);
   }
 }
\ No newline at end of file