diff --git a/src/main/java/io/iron/ironworker/client/APIException.java b/src/main/java/io/iron/ironworker/client/APIException.java
index 215c7dc..6c56b04 100644
--- a/src/main/java/io/iron/ironworker/client/APIException.java
+++ b/src/main/java/io/iron/ironworker/client/APIException.java
@@ -1,8 +1,8 @@
 package io.iron.ironworker.client;
 
 public class APIException extends Exception {
-    private String message;
-    private Exception innerException;
+    private final String message;
+    private final Exception innerException;
     
     public APIException(String message, Exception innerException) {
         this.message = message;
diff --git a/src/main/java/io/iron/ironworker/client/Client.java b/src/main/java/io/iron/ironworker/client/Client.java
index b2b5eef..3fb782f 100644
--- a/src/main/java/io/iron/ironworker/client/Client.java
+++ b/src/main/java/io/iron/ironworker/client/Client.java
@@ -17,8 +17,8 @@
 import java.util.Map;
 
 public class Client {
-    private APIClient api;
-    private Gson gson;
+    private final APIClient api;
+    private final Gson gson;
 
     public Client(String token, String projectId) {
         api = new APIClient(token, projectId);
diff --git a/src/main/java/io/iron/ironworker/client/builders/PaginationOptionsObject.java b/src/main/java/io/iron/ironworker/client/builders/PaginationOptionsObject.java
index c8465ff..a51091e 100644
--- a/src/main/java/io/iron/ironworker/client/builders/PaginationOptionsObject.java
+++ b/src/main/java/io/iron/ironworker/client/builders/PaginationOptionsObject.java
@@ -4,7 +4,7 @@
 import java.util.Map;
 
 public class PaginationOptionsObject {
-    private Map<String, Object> options;
+    private final Map<String, Object> options;
 
     public PaginationOptionsObject() {
         options = new HashMap<String, Object>();
diff --git a/src/main/java/io/iron/ironworker/client/builders/ParamsObject.java b/src/main/java/io/iron/ironworker/client/builders/ParamsObject.java
index a8fc067..697d5eb 100644
--- a/src/main/java/io/iron/ironworker/client/builders/ParamsObject.java
+++ b/src/main/java/io/iron/ironworker/client/builders/ParamsObject.java
@@ -4,7 +4,7 @@
 import java.util.Map;
 
 public class ParamsObject {
-    private Map<String, Object> params;
+    private final Map<String, Object> params;
 
     public ParamsObject() {
         params = new HashMap<String, Object>();
diff --git a/src/main/java/io/iron/ironworker/client/builders/ScheduleOptionsObject.java b/src/main/java/io/iron/ironworker/client/builders/ScheduleOptionsObject.java
index b5d45cd..0a1e879 100644
--- a/src/main/java/io/iron/ironworker/client/builders/ScheduleOptionsObject.java
+++ b/src/main/java/io/iron/ironworker/client/builders/ScheduleOptionsObject.java
@@ -5,7 +5,7 @@
 import java.util.Map;
 
 public class ScheduleOptionsObject {
-    private Map<String, Object> options;
+    private final Map<String, Object> options;
 
     public ScheduleOptionsObject() {
         options = new HashMap<String, Object>();
diff --git a/src/main/java/io/iron/ironworker/client/builders/TaskOptionsObject.java b/src/main/java/io/iron/ironworker/client/builders/TaskOptionsObject.java
index 37ad514..a0ac3e3 100644
--- a/src/main/java/io/iron/ironworker/client/builders/TaskOptionsObject.java
+++ b/src/main/java/io/iron/ironworker/client/builders/TaskOptionsObject.java
@@ -4,7 +4,7 @@
 import java.util.Map;
 
 public class TaskOptionsObject {
-    private Map<String, Object> options;
+    private final Map<String, Object> options;
 
     public TaskOptionsObject() {
         options = new HashMap<String, Object>();
diff --git a/src/main/java/io/iron/ironworker/client/builders/TaskProgressOptionsObject.java b/src/main/java/io/iron/ironworker/client/builders/TaskProgressOptionsObject.java
index c7c4315..dbfe215 100644
--- a/src/main/java/io/iron/ironworker/client/builders/TaskProgressOptionsObject.java
+++ b/src/main/java/io/iron/ironworker/client/builders/TaskProgressOptionsObject.java
@@ -4,7 +4,7 @@
 import java.util.Map;
 
 public class TaskProgressOptionsObject {
-    private Map<String, Object> options;
+    private final Map<String, Object> options;
 
     public TaskProgressOptionsObject() {
         options = new HashMap<String, Object>();
diff --git a/src/main/java/io/iron/ironworker/client/codes/BaseCode.java b/src/main/java/io/iron/ironworker/client/codes/BaseCode.java
index f3906ac..89cecc0 100644
--- a/src/main/java/io/iron/ironworker/client/codes/BaseCode.java
+++ b/src/main/java/io/iron/ironworker/client/codes/BaseCode.java
@@ -1,10 +1,10 @@
 package io.iron.ironworker.client.codes;
 
 public class BaseCode {
-    private String name;
-    private String file;
-    private String runtime;
-    private String runner;
+    private final String name;
+    private final String file;
+    private final String runtime;
+    private final String runner;
     private String stack;
 
     public BaseCode(String name, String file, String runtime, String runner) {
diff --git a/src/main/java/io/iron/ironworker/client/encryptors/PayloadEncryptor.java b/src/main/java/io/iron/ironworker/client/encryptors/PayloadEncryptor.java
index a772047..67ecedb 100644
--- a/src/main/java/io/iron/ironworker/client/encryptors/PayloadEncryptor.java
+++ b/src/main/java/io/iron/ironworker/client/encryptors/PayloadEncryptor.java
@@ -25,9 +25,9 @@ public class PayloadEncryptor {
     private static final int GCM_NONCE_LENGTH = 12; // in bytes
     private static final int GCM_TAG_LENGTH = 16; // in bytes (overhead)
 
-    private PublicKey rsaPublicKey;
-    private Key aesKey;
-    private SecureRandom secureRandom;
+    private final PublicKey rsaPublicKey;
+    private final Key aesKey;
+    private final SecureRandom secureRandom;
 
     public PayloadEncryptor(String encryptionKeyFile) throws GeneralSecurityException, IOException {
         Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());