minor clean up

Author: Stephane Landelle

api/src/main/java/org/asynchttpclient/cookie/Cookie.java

@@ -148,7 +148,7 @@ public boolean isHttpOnly() {
     public String toString() {
         StringBuilder buf = new StringBuilder();
         buf.append(name);
-        buf.append("=");
+        buf.append('=');
         buf.append(rawValue);
         if (domain != null) {
             buf.append("; domain=");
@@ -165,7 +165,7 @@ public String toString() {
         if (maxAge >= 0) {
             buf.append("; maxAge=");
             buf.append(maxAge);
-            buf.append("s");
+            buf.append('s');
         }
         if (secure) {
             buf.append("; secure");

api/src/main/java/org/asynchttpclient/resumable/PropertiesBasedResumableProcessor.java

@@ -88,7 +88,7 @@ public void save(Map<String, Long> map) {
     }
 
     private static String append(Map.Entry<String, Long> e) {
-        return new StringBuilder(e.getKey()).append("=").append(e.getValue()).append("\n").toString();
+        return new StringBuilder(e.getKey()).append('=').append(e.getValue()).append('\n').toString();
     }
 
     /**