public static void main(String[] args)throws Exception{     String jsonStr1="{\"access_token\":\"OezXcEiiBSKSxW0eoylIeIVb08lFhyeFsq6cUJJNo8XYLoJjqYARJOZUrnqhfvnyMKOSjz5SHPHGUmt6f09_762MWQ0HLnZtffDPyD2A6TgCqWlZAEsHLhIaaQVYx1lywxOWQTrr7rX13i_w1INGnw\",\"expires_in\":7200,\"openid\":\"owYTUs68SXYX83wBvm_uN4Ya****\",\"scope\":\"snsapi_base\"}";        String jsonStr2="{\"access_token\":\"OezXcEiiBSKSxW0eoylIeIVb08lFhyeFsq6cUJJNo8XYLoJjqYARJOZUrnqhfvnyMKOSjz5SHPHGUmt6f09_762MWQ0HLnZtffDPyD2A6TgCqWlZAEsHLhIaaQVYx1lywxOWQTrr7rX13i_w1INGnw\",\"expires_in\":7200,\"refresh_token\":\"OezXcEiiBSKSxW0eoylIeIVb08lFhyeFsq6cUJJNo8XYLoJjqYARJOZUrnqhfvnyuq9ojibRxolf9ElS7PSM0Kz1OTNlJ8ZKJl2BfbPi0LA-nQ9uNVUE8ujLFsdCeP79_L9FmIYcmHLXWXnl-fUsVg\",\"openid\":\"owYTUs68SXYX83wBvm_uN4Y****\",\"scope\":\"snsapi_base\"}";        JSONObject json1=JSONObject.fromObject(jsonStr1);    JSONObject json2=JSONObject.fromObject(jsonStr2);    String refresh_token_1=null;    String refresh_token_2=null;    if(json1.containsKey("refresh_token")){        refresh_token_1=json1.getString("refresh_token");    }    if(json2.containsKey("refresh_token")){        refresh_token_2=json2.getString("refresh_token");    }        System.out.println(refresh_token_1);    System.out.println(refresh_token_2);}

运行结果:nullOezXcEiiBSKSxW0eoylIeIVb08lFhyeFsq6cUJJNo8XYLoJjqYARJOZUrnqhfvnyuq9ojibRxolf9ElS7PSM0Kz1OTNlJ8ZKJl2BfbPi0LA-nQ9uNVUE8ujLFsdCeP79_L9FmIYcmHLXWXnl-fUsVg