diff --git a/EXAMPLES.md b/EXAMPLES.md
index 8a849303..995e4c1d 100644
--- a/EXAMPLES.md
+++ b/EXAMPLES.md
@@ -127,4 +127,4 @@ RSAKeyProvider keyProvider = new RSAKeyProvider() {
 
 Algorithm algorithm = Algorithm.RSA256(keyProvider);
 //Use the Algorithm to create and verify JWTs.
-```
\ No newline at end of file
+```
diff --git a/LICENSE b/LICENSE
index 4a7a13ad..bcd1854c 100644
--- a/LICENSE
+++ b/LICENSE
@@ -18,4 +18,4 @@ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
\ No newline at end of file
+SOFTWARE.
diff --git a/lib/src/main/java/com/auth0/jwt/JWTCreator.java b/lib/src/main/java/com/auth0/jwt/JWTCreator.java
index a99f0fa0..7ed83940 100644
--- a/lib/src/main/java/com/auth0/jwt/JWTCreator.java
+++ b/lib/src/main/java/com/auth0/jwt/JWTCreator.java
@@ -7,6 +7,7 @@
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.MapperFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.json.JsonMapper;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 
 import java.nio.charset.StandardCharsets;
@@ -31,12 +32,14 @@ public final class JWTCreator {
     private static final SimpleModule module;
 
     static {
-        mapper = new ObjectMapper();
         module = new SimpleModule();
         module.addSerializer(PayloadClaimsHolder.class, new PayloadSerializer());
         module.addSerializer(HeaderClaimsHolder.class, new HeaderSerializer());
-        mapper.registerModule(module);
-        mapper.configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true);
+
+        mapper = JsonMapper.builder()
+                .configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true)
+                .build()
+                .registerModule(module);
     }
 
     private JWTCreator(Algorithm algorithm, Map<String, Object> headerClaims, Map<String, Object> payloadClaims)
@@ -489,7 +492,7 @@ private static boolean validateClaim(Map<?, ?> map) {
                     return false;
                 }
 
-                if (entry.getKey() == null || !(entry.getKey() instanceof String)) {
+                if (!(entry.getKey() instanceof String)) {
                     return false;
                 }
             }
diff --git a/lib/src/main/java/com/auth0/jwt/algorithms/RSAAlgorithm.java b/lib/src/main/java/com/auth0/jwt/algorithms/RSAAlgorithm.java
index 0c7a5b57..ca892e60 100644
--- a/lib/src/main/java/com/auth0/jwt/algorithms/RSAAlgorithm.java
+++ b/lib/src/main/java/com/auth0/jwt/algorithms/RSAAlgorithm.java
@@ -5,7 +5,6 @@
 import com.auth0.jwt.interfaces.DecodedJWT;
 import com.auth0.jwt.interfaces.RSAKeyProvider;
 
-import java.nio.charset.StandardCharsets;
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
 import java.security.SignatureException;
diff --git a/lib/src/main/java/com/auth0/jwt/impl/BasicHeader.java b/lib/src/main/java/com/auth0/jwt/impl/BasicHeader.java
index 3746dcd2..8031d8c0 100644
--- a/lib/src/main/java/com/auth0/jwt/impl/BasicHeader.java
+++ b/lib/src/main/java/com/auth0/jwt/impl/BasicHeader.java
@@ -37,7 +37,7 @@ class BasicHeader implements Header, Serializable {
         this.type = type;
         this.contentType = contentType;
         this.keyId = keyId;
-        this.tree = Collections.unmodifiableMap(tree == null ? new HashMap<String, JsonNode>() : tree);
+        this.tree = Collections.unmodifiableMap(tree == null ? new HashMap<>() : tree);
         this.objectReader = objectReader;
     }
 
diff --git a/lib/src/test/java/com/auth0/jwt/ConcurrentVerifyTest.java b/lib/src/test/java/com/auth0/jwt/ConcurrentVerifyTest.java
index a06df7b7..32ede1de 100644
--- a/lib/src/test/java/com/auth0/jwt/ConcurrentVerifyTest.java
+++ b/lib/src/test/java/com/auth0/jwt/ConcurrentVerifyTest.java
@@ -10,14 +10,11 @@
 import org.junit.rules.ExpectedException;
 
 import java.security.interfaces.ECKey;
-import java.security.interfaces.ECPrivateKey;
-import java.security.interfaces.ECPublicKey;
 import java.security.interfaces.RSAKey;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.*;
 
-import static com.auth0.jwt.PemUtils.readPrivateKeyFromFile;
 import static com.auth0.jwt.PemUtils.readPublicKeyFromFile;
 
 //@Ignore("Skipping concurrency tests")
diff --git a/lib/src/test/java/com/auth0/jwt/JWTCreatorTest.java b/lib/src/test/java/com/auth0/jwt/JWTCreatorTest.java
index 020e5e37..8fc83b44 100644
--- a/lib/src/test/java/com/auth0/jwt/JWTCreatorTest.java
+++ b/lib/src/test/java/com/auth0/jwt/JWTCreatorTest.java
@@ -16,9 +16,7 @@
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.*;
-import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
-import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
diff --git a/lib/src/test/java/com/auth0/jwt/algorithms/HMACAlgorithmTest.java b/lib/src/test/java/com/auth0/jwt/algorithms/HMACAlgorithmTest.java
index 4a0269cc..9b6ac0c0 100644
--- a/lib/src/test/java/com/auth0/jwt/algorithms/HMACAlgorithmTest.java
+++ b/lib/src/test/java/com/auth0/jwt/algorithms/HMACAlgorithmTest.java
@@ -13,7 +13,6 @@
 import java.nio.charset.StandardCharsets;
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
-import java.util.Arrays;
 
 import static com.auth0.jwt.algorithms.CryptoTestHelper.asJWT;
 import static com.auth0.jwt.algorithms.CryptoTestHelper.assertSignaturePresent;
diff --git a/settings.gradle b/settings.gradle
index a4cda2d7..8d5f112c 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -8,4 +8,4 @@ pluginManagement {
 }
 
 include ':java-jwt'
-project(':java-jwt').projectDir = new File(rootProject.projectDir, '/lib')
\ No newline at end of file
+project(':java-jwt').projectDir = new File(rootProject.projectDir, '/lib')