diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/Authorization.java b/acme4j-client/src/main/java/org/shredzone/acme4j/Authorization.java
index f26ca01b..98c59820 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/Authorization.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/Authorization.java
@@ -118,7 +118,7 @@ public class Authorization extends AcmeResource {
     @SuppressWarnings("unchecked")
     public <T extends Challenge> T findChallenge(String type) {
         Collection<Challenge> result = findCombination(type);
-        return (result != null ? (T) result.iterator().next() : null);
+        return result != null ? (T) result.iterator().next() : null;
     }
 
     /**
@@ -217,6 +217,7 @@ public class Authorization extends AcmeResource {
                 update();
             } catch (AcmeRetryAfterException ex) {
                 // ignore... The object was still updated.
+                LOG.debug("Retry-After", ex);
             } catch (AcmeException ex) {
                 throw new AcmeProtocolException("Could not load lazily", ex);
             }
@@ -233,47 +234,47 @@ public class Authorization extends AcmeResource {
     protected void unmarshalAuthorization(Map<String, Object> json) {
         this.status = Status.parse((String) json.get("status"), Status.PENDING);
 
-        String expires = (String) json.get("expires");
-        if (expires != null) {
-            this.expires = TimestampParser.parse(expires);
+        String jsonExpires = (String) json.get("expires");
+        if (jsonExpires != null) {
+            expires = TimestampParser.parse(jsonExpires);
         }
 
-        Map<String, Object> identifier = (Map<String, Object>) json.get("identifier");
-        if (identifier != null) {
-            String type = (String) identifier.get("type");
+        Map<String, Object> jsonIdentifier = (Map<String, Object>) json.get("identifier");
+        if (jsonIdentifier != null) {
+            String type = (String) jsonIdentifier.get("type");
             if (type != null && !"dns".equals(type)) {
                 throw new AcmeProtocolException("Unknown authorization type: " + type);
             }
-            this.domain = (String) identifier.get("value");
+            domain = (String) jsonIdentifier.get("value");
         }
 
-        Collection<Map<String, Object>> challenges =
+        Collection<Map<String, Object>> jsonChallenges =
                         (Collection<Map<String, Object>>) json.get("challenges");
         List<Challenge> cr = new ArrayList<>();
-        for (Map<String, Object> c : challenges) {
+        for (Map<String, Object> c : jsonChallenges) {
             Challenge ch = getSession().createChallenge(c);
             if (ch != null) {
                 cr.add(ch);
             }
         }
-        this.challenges = cr;
+        challenges = cr;
 
-        Collection<List<Number>> combinations =
+        Collection<List<Number>> jsonCombinations =
                         (Collection<List<Number>>) json.get("combinations");
-        if (combinations != null) {
-            List<List<Challenge>> cmb = new ArrayList<>(combinations.size());
-            for (List<Number> c : combinations) {
+        if (jsonCombinations != null) {
+            List<List<Challenge>> cmb = new ArrayList<>(jsonCombinations.size());
+            for (List<Number> c : jsonCombinations) {
                 List<Challenge> clist = new ArrayList<>(c.size());
                 for (Number n : c) {
                     clist.add(cr.get(n.intValue()));
                 }
                 cmb.add(clist);
             }
-            this.combinations = cmb;
+            combinations = cmb;
         } else {
             List<List<Challenge>> cmb = new ArrayList<>(1);
             cmb.add(cr);
-            this.combinations = cmb;
+            combinations = cmb;
         }
 
         loaded = true;
diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/Metadata.java b/acme4j-client/src/main/java/org/shredzone/acme4j/Metadata.java
index 3354d09d..7882d255 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/Metadata.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/Metadata.java
@@ -79,7 +79,7 @@ public class Metadata {
      */
     public String get(String key) {
         Object value = meta.get(key);
-        return (value != null ? value.toString() : null);
+        return value != null ? value.toString() : null;
     }
 
     /**
@@ -95,7 +95,7 @@ public class Metadata {
     public URI getUri(String key) {
         Object uri = meta.get(key);
         try {
-            return (uri != null ? new URI(uri.toString()) : null);
+            return uri != null ? new URI(uri.toString()) : null;
         } catch (URISyntaxException ex) {
             throw new AcmeProtocolException("Bad URI: " + uri, ex);
         }
diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/Registration.java b/acme4j-client/src/main/java/org/shredzone/acme4j/Registration.java
index 4d8314a2..0541b41a 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/Registration.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/Registration.java
@@ -335,6 +335,7 @@ public class Registration extends AcmeResource {
                 update();
             } catch (AcmeRetryAfterException ex) {
                 // ignore... The object was still updated.
+                LOG.debug("Retry-After", ex);
             } catch (AcmeException ex) {
                 throw new AcmeProtocolException("Could not load lazily", ex);
             }
diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/Status.java b/acme4j-client/src/main/java/org/shredzone/acme4j/Status.java
index 47936725..f0e8f8de 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/Status.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/Status.java
@@ -29,11 +29,13 @@ public enum Status {
      *         no match
      */
     public static Status parse(String str) {
-        try {
-            return valueOf(str.toUpperCase());
-        } catch (IllegalArgumentException ex) {
-            return Status.UNKNOWN;
+        String check = str.toUpperCase();
+        for (Status s : values()) {
+            if (s.name().equals(check)) {
+                return s;
+            }
         }
+        return Status.UNKNOWN;
     }
 
     /**
@@ -47,7 +49,7 @@ public enum Status {
      *         no match, or {@code def} if the str was {@code null}
      */
     public static Status parse(String str, Status def) {
-        return (str != null ? parse(str) : def);
+        return str != null ? parse(str) : def;
     }
 
 }
diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/connector/DefaultConnection.java b/acme4j-client/src/main/java/org/shredzone/acme4j/connector/DefaultConnection.java
index d7f5f3b8..336c51a9 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/connector/DefaultConnection.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/connector/DefaultConnection.java
@@ -198,7 +198,8 @@ public class DefaultConnection implements Connection {
 
         String response = "";
         try {
-            InputStream in = (conn.getResponseCode() < 400 ? conn.getInputStream() : conn.getErrorStream());
+            InputStream in =
+                    conn.getResponseCode() < 400 ? conn.getInputStream() : conn.getErrorStream();
             if (in != null) {
                 response = readStream(in);
                 result = JsonUtil.parseJson(response);
@@ -311,7 +312,7 @@ public class DefaultConnection implements Connection {
             }
         }
 
-        return (!result.isEmpty() ? result : null);
+        return !result.isEmpty() ? result : null;
     }
 
     @Override
@@ -334,7 +335,7 @@ public class DefaultConnection implements Connection {
 
             // HTTP-date
             long date = conn.getHeaderFieldDate("Retry-After", 0L);
-            return (date != 0 ? new Date(date) : null);
+            return date != 0 ? new Date(date) : null;
         } catch (Exception ex) {
             throw new AcmeProtocolException("Bad retry-after header value: " + header, ex);
         }
@@ -410,12 +411,13 @@ public class DefaultConnection implements Connection {
      * Log all HTTP headers in debug mode.
      */
     private void logHeaders() {
-        if (LOG.isDebugEnabled()) {
-            Map<String, List<String>> headers = conn.getHeaderFields();
-            for (String key : headers.keySet()) {
-                for (String value : headers.get(key)) {
-                    LOG.debug("HEADER {}: {}", key, value);
-                }
+        if (!LOG.isDebugEnabled()) {
+            return;
+        }
+
+        for (Map.Entry<String, List<String>> entry : conn.getHeaderFields().entrySet()) {
+            for (String value : entry.getValue()) {
+                LOG.debug("HEADER {}: {}", entry.getKey(), value);
             }
         }
     }
diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/connector/HttpConnector.java b/acme4j-client/src/main/java/org/shredzone/acme4j/connector/HttpConnector.java
index 78073734..433b6efb 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/connector/HttpConnector.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/connector/HttpConnector.java
@@ -14,10 +14,13 @@
 package org.shredzone.acme4j.connector;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.net.HttpURLConnection;
 import java.net.URI;
 import java.util.Properties;
 
+import org.slf4j.LoggerFactory;
+
 /**
  * A generic HTTP connector. It connects to the given URI with a 10 seconds connection and
  * read timeout.
@@ -32,16 +35,17 @@ public class HttpConnector {
 
     static {
         StringBuilder agent = new StringBuilder("acme4j");
-        try {
+
+        try (InputStream in = HttpConnector.class.getResourceAsStream("/org/shredzone/acme4j/version.properties")) {
             Properties prop = new Properties();
-            prop.load(HttpConnector.class.getResourceAsStream("/org/shredzone/acme4j/version.properties"));
+            prop.load(in);
             agent.append('/').append(prop.getProperty("version"));
         } catch (IOException ex) {
             // Ignore, just don't use a version
+            LoggerFactory.getLogger(HttpConnector.class).warn("Could not read library version", ex);
         }
 
         agent.append(" Java/").append(System.getProperty("java.version"));
-
         USER_AGENT = agent.toString();
     }
 
diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/exception/AcmeRateLimitExceededException.java b/acme4j-client/src/main/java/org/shredzone/acme4j/exception/AcmeRateLimitExceededException.java
index 19102d45..24b4a185 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/exception/AcmeRateLimitExceededException.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/exception/AcmeRateLimitExceededException.java
@@ -44,7 +44,8 @@ public class AcmeRateLimitExceededException extends AcmeServerException {
     public AcmeRateLimitExceededException(String type, String detail, Date retryAfter, Collection<URI> documents) {
         super(type, detail);
         this.retryAfter = retryAfter;
-        this.documents = (documents != null ? Collections.unmodifiableCollection(documents) : null);
+        this.documents =
+                documents != null ? Collections.unmodifiableCollection(documents) : null;
     }
 
     /**
@@ -52,7 +53,7 @@ public class AcmeRateLimitExceededException extends AcmeServerException {
      * moment is not known.
      */
     public Date getRetryAfter() {
-        return (retryAfter != null ? new Date(retryAfter.getTime()) : null);
+        return retryAfter != null ? new Date(retryAfter.getTime()) : null;
     }
 
     /**
diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/exception/AcmeRetryAfterException.java b/acme4j-client/src/main/java/org/shredzone/acme4j/exception/AcmeRetryAfterException.java
index e9669fca..c8d7c904 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/exception/AcmeRetryAfterException.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/exception/AcmeRetryAfterException.java
@@ -33,7 +33,7 @@ public class AcmeRetryAfterException extends AcmeException {
      * Returns the retry-after date returned by the server.
      */
     public Date getRetryAfter() {
-        return (retryAfter != null ? new Date(retryAfter.getTime()) : null);
+        return retryAfter != null ? new Date(retryAfter.getTime()) : null;
     }
 
 }
diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/util/TimestampParser.java b/acme4j-client/src/main/java/org/shredzone/acme4j/util/TimestampParser.java
index 375f6ace..285d54cb 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/util/TimestampParser.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/util/TimestampParser.java
@@ -25,7 +25,7 @@ import java.util.regex.Pattern;
  *
  * @see <a href="https://www.ietf.org/rfc/rfc3339.txt">RFC 3339</a>
  */
-public class TimestampParser {
+public final class TimestampParser {
 
     private static final Pattern DATE_PATTERN = Pattern.compile(
                   "^(\\d{4})-(\\d{2})-(\\d{2})T"
@@ -36,6 +36,10 @@ public class TimestampParser {
     private static final Pattern TZ_PATTERN = Pattern.compile(
                   "([+-])(\\d{2}):?(\\d{2})$");
 
+    private TimestampParser() {
+        // Utility class without constructor
+    }
+
     /**
      * Parses a RFC 3339 formatted date.
      *
@@ -58,15 +62,14 @@ public class TimestampParser {
         int minute = Integer.parseInt(m.group(5));
         int second = Integer.parseInt(m.group(6));
 
-        String msStr = m.group(7);
-        if (msStr == null) {
-            msStr = "000";
-        } else {
-            while (msStr.length() < 3) {
-                msStr += '0';
-            }
+        StringBuilder msStr = new StringBuilder();
+        if (m.group(7) != null) {
+            msStr.append(m.group(7));
         }
-        int ms = Integer.parseInt(msStr);
+        while (msStr.length() < 3) {
+            msStr.append('0');
+        }
+        int ms = Integer.parseInt(msStr.toString());
 
         String tz = m.group(8);
         if ("Z".equalsIgnoreCase(tz)) {