diff --git a/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/model/AwsProxyRequest.java b/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/model/AwsProxyRequest.java
index df9758503..6e9cda4c0 100644
--- a/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/model/AwsProxyRequest.java
+++ b/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/model/AwsProxyRequest.java
@@ -43,17 +43,17 @@ public class AwsProxyRequest {
 
     @JsonIgnore
     public String getQueryString() {
-        String params = "";
+        StringBuilder params = new StringBuilder("");
 
         if (this.getQueryStringParameters() != null && this.getQueryStringParameters().size() > 0) {
             for (String key : this.getQueryStringParameters().keySet()) {
-                String separator = params.equals("") ? "?" : "&";
+                String separator = params.length() == 0 ? "?" : "&";
 
-                params += separator + key + "=" + this.getQueryStringParameters().get(key);
+                params.append(separator + key + "=" + this.getQueryStringParameters().get(key));
             }
         }
 
-        return params;
+        return params.toString();
     }
 
 
diff --git a/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsProxyHttpServletRequest.java b/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsProxyHttpServletRequest.java
index cc3ef769b..9c880eb4a 100644
--- a/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsProxyHttpServletRequest.java
+++ b/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsProxyHttpServletRequest.java
@@ -420,17 +420,17 @@ public void setCharacterEncoding(String s) throws UnsupportedEncodingException {
 
         if (currentContentType.contains(HEADER_VALUE_SEPARATOR)) {
             String[] contentTypeValues = currentContentType.split(HEADER_VALUE_SEPARATOR);
-            String contentType = contentTypeValues[0];
+            StringBuilder contentType = new StringBuilder(contentTypeValues[0]);
 
             for (String contentTypeValue : contentTypeValues) {
                 if (contentTypeValue.trim().startsWith(ENCODING_VALUE_KEY)) {
-                    contentType += HEADER_VALUE_SEPARATOR + " " + ENCODING_VALUE_KEY + HEADER_KEY_VALUE_SEPARATOR + s;
+                    contentType.append(HEADER_VALUE_SEPARATOR + " " + ENCODING_VALUE_KEY + HEADER_KEY_VALUE_SEPARATOR + s);
                 } else {
-                    contentType += HEADER_VALUE_SEPARATOR + " " + contentTypeValue;
+                    contentType.append(HEADER_VALUE_SEPARATOR + " " + contentTypeValue);
                 }
             }
 
-            request.getHeaders().put(HttpHeaders.CONTENT_TYPE, contentType);
+            request.getHeaders().put(HttpHeaders.CONTENT_TYPE, contentType.toString());
         } else {
             request.getHeaders().put(
                     HttpHeaders.CONTENT_TYPE,
diff --git a/aws-serverless-java-container-spring/src/main/java/com/amazonaws/serverless/proxy/spring/LambdaSpringApplicationInitializer.java b/aws-serverless-java-container-spring/src/main/java/com/amazonaws/serverless/proxy/spring/LambdaSpringApplicationInitializer.java
index 82b82c294..50810dea4 100644
--- a/aws-serverless-java-container-spring/src/main/java/com/amazonaws/serverless/proxy/spring/LambdaSpringApplicationInitializer.java
+++ b/aws-serverless-java-container-spring/src/main/java/com/amazonaws/serverless/proxy/spring/LambdaSpringApplicationInitializer.java
@@ -130,7 +130,7 @@ private void notifyStartListeners(ServletContext context) {
      * Default configuration class for the DispatcherServlet. This just mocks the behaviour of a default
      * ServletConfig object with no init parameters
      */
-    private class DefaultDispatcherConfig implements ServletConfig {
+    private static class DefaultDispatcherConfig implements ServletConfig {
         private ServletContext servletContext;
 
         DefaultDispatcherConfig(ServletContext context) {