Apply simplification suggested by @johnjaylward.

src/main/java/org/json/JSONObject.java

@@ -253,13 +253,12 @@ public class JSONObject {
             switch (x.nextClean()) {
             case ';':
             case ',':
-                c = x.nextClean();
+                if (x.nextClean() == '}') {
-                if (c == 0) {
-                    throw x.syntaxError("A JSONObject text must end with '}'");
-                }
-                if (c == '}') {
                     return;
                 }
+                if (x.end()) {
+                    throw x.syntaxError("A JSONObject text must end with '}'");
+                }
                 x.back();
                 break;
             case '}':