Serializing data from two URLs in the same object efficiently

This is a follow-up to: Serializing JSON data coming from two URLs in the same object

I have two URLs (urlA and urlB) and they both give me a JSON response back in the same JSON format. Below is my JSON string which I am getting back by calling from urlA. I have shortened it down by having only three reportRecords for understanding purposes. In general, it might have more than ~500 reportRecords.

```
{
"aggRecords": {
"reportRecords": [
{
"min": 0,
"max": 12,
"avg": 0.3699187,
"count": 246,
"sumSq": 571,
"stddev": 1.4779372,
"median": 0,
"percentileMap": {
"95": 4
},
"metricName": "TransactionDuration",
"dimensions": {
"env": "dev",
"pool": "titan",
"Name": "PostProcessing",
"Type": "PostProcessing"
},
"value": 91
},
{
"min": 0,
"max": 23,
"avg": 2.3991289E-4,
"count": 1463031,
"sumSq": 3071,
"stddev": 0.045814946,
"median": 0,
"percentileMap": {
"95": 0
},
"metricName": "TransactionDuration",
"dimensions": {
"env": "dev",
"pool": "titan",
"Name": "ResourceContext",
"Type": "ResourceContext"
},
"value": 351
},
{
"min": 0,
"max": 1209,
"avg": 1.9203402,
"count": 7344636,
"sumSq": 71832774,
"stddev": 2.4683187,
"median": 2,
"percentileMap": {
"95": 4
},
"metricName": "TransactionDuration",
"dimensions": {
"env": "dev",
"pool": "titan",
"Name": "DataSync",

The main method is doing too much. It would be better to extract its content to a method, with a meaningful name.

I don't really see the point of this:

List hostMetricsList = new ArrayList();
for (String hostName : hostNames) {
    // ...
    HostMetrics hostMetrics = new HostMetrics(hostName, startDate, endDate);
    hostMetricsList.add(hostMetrics);
}
System.out.println(hostMetricsList);

Do you really want to print out the HostMetrics as a list? Printing them one by one is not good enough?

for (String hostName : hostNames) {
    // ...
    HostMetrics hostMetrics = new HostMetrics(hostName, startDate, endDate);
    System.out.println(hostMetrics);
}

I don't know of a rule against cloning and passing around Calendar objects, but it just doesn't seem natural. Instead of this:

Calendar startDate = new GregorianCalendar();
startDate.set(Calendar.MINUTE, 0);
Calendar endDate = (Calendar) startDate.clone();
startDate.set(Calendar.HOUR_OF_DAY, 0);
HostMetrics hostMetrics = new HostMetrics(hostName, startDate, endDate);

I would do like this:

Calendar cal = new GregorianCalendar();
cal.set(Calendar.MINUTE, 0);
Date startDate = cal.getTime();
cal.set(Calendar.HOUR_OF_DAY, 0);
Date endDate = cal.getTime();

HostMetrics hostMetrics = new HostMetrics(hostName, startDate, endDate);

This means of course that you'll have to change the HostMetrics constructor to take Date params instead of Calendar, but I think that's a good thing.

Here, appending the startTime and endTime parameters is duplicated:

String urlA = BASE_URL + hostName + TRANSACTION_METRIC + "&startTime=" + startTime
        + "&endTime=" + endTime;

String urlB = BASE_URL + hostName + EVENT_METRIC + "&startTime=" + startTime
        + "&endTime=" + endTime;

I would extract the duplicated parts to a temp variable:

String extraParams = "&startTime=" + startTime + "&endTime=" + endTime;
String urlA = BASE_URL + hostName + TRANSACTION_METRIC + extraParams;
String urlB = BASE_URL + hostName + EVENT_METRIC + extraParams;

Sometimes you call a hostname variable as hostname, sometimes hostName. One day you might mix them up. I recommend to use hostname everywhere consistently.

StackExchange Code Review Q#61578, answer score: 2