Update conditions to use Stringbuilder instead of StringJoiner for compatibility with Android.

Author: The-inside-man

core-api/src/main/java/com/optimizely/ab/config/audience/AndCondition.java

@@ -76,11 +76,13 @@ public String getOperandOrId() {
 
     @Override
     public String toJson() {
-        StringJoiner s = new StringJoiner(", ", "[", "]");
-        s.add("\"and\"");
+        StringBuilder s = new StringBuilder();
+        s.append("[\"and\"");
         for (int i = 0; i < conditions.size(); i++) {
-            s.add(conditions.get(i).toJson());
+            s.append(conditions.get(i).toJson());
+            s.append(", ");
         }
+        s.append("]");
         return s.toString();
     }
 

core-api/src/main/java/com/optimizely/ab/config/audience/NotCondition.java

@@ -56,9 +56,10 @@ public String getOperandOrId() {
 
     @Override
     public String toJson() {
-        StringJoiner s = new StringJoiner(", ","[","]");
-        s.add("\"not\"");
-        s.add(condition.toJson());
+        StringBuilder s = new StringBuilder();
+        s.append("[\"not\"");
+        s.append(condition.toJson());
+        s.append("]");
         return s.toString();
     }
 

core-api/src/main/java/com/optimizely/ab/config/audience/OrCondition.java

@@ -74,11 +74,13 @@ public String getOperandOrId() {
 
     @Override
     public String toJson() {
-        StringJoiner s = new StringJoiner(", ", "[", "]");
-        s.add("\"or\"");
+        StringBuilder s = new StringBuilder();
+        s.append("[\"or\"");
         for (int i = 0; i < conditions.size(); i++) {
-            s.add(conditions.get(i).toJson());
+            s.append(conditions.get(i).toJson());
+            s.append(", ");
         }
+        s.append("]");
         return s.toString();
     }