Replace instances of StringBuffer with StringBuilder

core/src/processing/data/JSONArray.java

@@ -1224,7 +1224,7 @@ public class JSONArray {
    */
   public String join(String separator) {
     int len = this.size();
-    StringBuffer sb = new StringBuffer();
+    StringBuilder sb = new StringBuilder();
 
     for (int i = 0; i < len; i += 1) {
       if (i > 0) {