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Sort Array object by date of its field

I have an Object MyTimes and in that object there are fields name ,start_date and configuration.
I have an array of this object, MyTimes [] mytimes
I am trying to sort the array by the start time but am struggling how to go about it.
The start_time field is a string, so this needs converting to a datetime.
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
for(int i=0; i<mytimes.length; i++) {
Date date = formatter.parse(mytimes[i].getStartTime());
}
I'd then put the date into an array list perhaps and then sort by datetime? But then I wouldnt know which start_time corresponds with which mytimes object...
What is the most efficient way of doing this?

Under the right circumstances this is a one-liner:
Arrays.sort(myTimes, Comparator.comparing(MyTimes::getStartDate));
Let’s see it in action:
MyTimes[] myTimes = {
new MyTimes("Polly", "2019-03-06T17:00:00Z"),
new MyTimes("Margaret", "2019-03-08T09:00:00Z"),
new MyTimes("Jane", "2019-03-01T06:00:00Z")
};
Arrays.sort(myTimes, Comparator.comparing(MyTimes::getStartDate));
Arrays.stream(myTimes).forEach(System.out::println);
Output:
Jane 2019-03-01T06:00:00Z
Polly 2019-03-06T17:00:00Z
Margaret 2019-03-08T09:00:00Z
I am assuming that getStartDate returns an Instant or another type the natural order of which agrees with the chronological order you want. For example:
public class MyTimes {
private String name;
private Instant startDate;
// Constructor, getters, toString, etc.
}
If you are receiving your start dates as strings somehow, you may write a convenient constructor that accepts a string for start date. I am already using such a constructor in the above snippet. One possibility is having two constructors:
public MyTimes(String name, Instant startDate) {
this.name = name;
this.startDate = startDate;
}
public MyTimes(String name, String startDate) {
this(name, Instant.parse(startDate));
}
The Instant class is part of java.time, the modern Java date and time API.
I am exploiting the fact that your strings are in the ISO 8601 format for an instant, the format that Instant.parse accepts and parses.
Avoid SimpleDateFormat and Date
I recommend you don’t use SimpleDateFormat and Date. Those classes are poorly designed and long outdated, the former in particular notoriously troublesome. There is also an error in your format pattern string for parsing: Z (pronounced “Zulu”) means UTC, and of you don’t parse it as such, you will get incorrect times (on most JVMs). Instant.parse efficiently avoids any problems here.
Don’t store date-tine as a string
It looks like you are are storing start time in a String field in your object? That would be poor modelling. Use a proper date-time type. Strings are for interfaces. Date-time classes like Instant offer much more functionality, for example define sort order.

You have two main approaches:
Make your class implement Comparable
Use a custom Comparator
Then, you can choose the field to compare from, and transform it.
IE (implementing comparable):
class Example implements Comparable<Example> {
private String stringDate;
public int compareTo(Example e) {
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
Date date1 = formatter.parse(this.stringDate);
Date date2 = formatter.parse(e.stringDate);
return date1.getTime() - date2.getTime();
}
}
And then using Arrays.sort would use your custom comparison.

Let your class implement Comparable and implement compareTo using modern formatting and date classes. Note that LocalDateTime also implements Comparable so once the string has been parsed you let LocalDateTime do the comparison
public class MyTimes implements Comparable<MyTimes> {
private final DateTimeFormatter dtf = DateTimeFormatter.ISO_INSTANT;
//other code
public int compareTo(MyTimes o) {
LocalDateTime thisDate = LocalDateTime.from(dtf.parse(this.getStartTime()));
LocalDateTime otherDate = LocalDateTime.from(dtf.parse(o.getStartTime()));
return thisDate.compareTo(otherDate);
}
}
You can also create a separate class as a comparator if this comparison is special and what you not always want to use
public class MyTimesComparator implements Comparator<MyTimes> {
#Override
public int compare(MyTimes arg0, MyTimes arg1) {
DateTimeFormatter dtf = DateTimeFormatter.ISO_INSTANT;
LocalDateTime thisDate = LocalDateTime.from(dtf.parse(this.getStartTime()));
LocalDateTime otherDate = LocalDateTime.from(dtf.parse(o.getStartTime()));
return thisDate.compareTo(otherDate);
}
}
and then use it like
someList.sort(new MyTimesComparator());
or use an inline function (I am using Instant here)
someList.sort( (m1, m2) -> {
DateTimeFormatter dtf = DateTimeFormatter.ISO_INSTANT;
Instant instant1 = Instant.from(dtf.parse(m1.getStartTime));
Instant instant2 = Instant.from(dtf.parse(m2.getStartTime));
return intant1.compareTo(instant2);
});
I noticed now that you have an array and not a list so you need to convert to a list or use Arrays.sort instead.

convert object into date

I get an ArrayList of Object[] from a database and I want to convert the java.sql.Date stored in an object into a java.util.Date (in order to use it in jfreechart):
my code is as follows:
fills up the Array of object with data from MySQL
ArrayList<Object[]> mydata=new ArrayList<>();
mydata=sqlGetter.getMdbObjectList(sqlString, null);
for(Object[] myobject : mydata){
if (myobject[1].getClass()==java.sql.Date.class){
java.util.Date mydate=null;
mydate = Date ( myobject[1]);
}
}
Netbeans return an error: "Java incompatible types: Object cannot be converted to Date"
While I understand the idea, I would have expected to be able to cast the object into a Date after having checked that it is indeed of the right class.
I'm starting java, so please any helps on the obvious mistake that I must be doing would be useful.

You are missing a cast. Additionally, you'd be better off using the instanceof operator:
for(Object[] myobject : mydata){
// Note that java.sql.Date extends java.util.Date
if (myobject[1] instanceof java.util.Date) {
java.util.Date mydate = (java.util.Date) myobject[1];
}
}

you just need to explicit cast the object to Date
ex: (Date) obj;

How to Increment date type value like Calendar Type

I am newbie to java, I want to add a Date type in table's column using native query.
But I have to increment my time by x minutes and then add.
In java :
we have calendar.add() method but I have to insert in Database as Date type
Here's the sample code :
Calendar now = Calendar.getInstance();
now.add(Calendar.MINUTE, 60*48);
But in DB I have to insert Date type as :
here:
Date currentTime = new java.sql.Date(new java.util.Date().getTime());
ResultSet resultset = obdnumberbo.getlist(userCallDetail.getaPartyMsisdn(),userCallDetail.getbPartyMsisdn(),currentTime,Jobname);
I want to do something with currenTime and increment it like add() method in Calendar class.
Also there is no way to cast calendar type object into date type.
Can anyone suggest a way?
Can any one suggest how to do this?

Comparing Converting ISO8601-compliant date with Java date?

As per this question, I have found how to parse the Solr date, but I am still unable to compare it with Java date.
DateTimeFormatter parser2 = ISODateTimeFormat.dateTimeNoMillis();
String jtdate = "2010-01-01T12:00:00+01:00";
System.out.println(parser2.parseDateTime(jtdate));
Currently I have got date in this format : 2013-07-28T13:48:02Z and I need to apply compareTo() operator on this date with current date from Java.

Assuming you do not care about the time, consider using DateTimeComparator.getDateOnlyInstance(), which is a Comparator that ignores the time fields when making the comparison, e.g.:
final DateTime a = parser2.parseDateTime(jtdate);
final Date b = new Date();
DateTimeComparator comparator = DateTimeComparator.getDateOnlyInstance();
comparator.compare(a, b);
Or,
comparator.compare(a, DateTime.now());

Compare string date to current long time

A search API is returning date in String format,I want to compare that date with current date and do something. I created a date object and parsed it but still getting error when I do the compare.
Calendar currentDate = Calendar.getInstance();
long dateNow = currentDate.getTimeInMillis();
String eventDate = meta.getString("startDate"); //This is the string API returns
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd kk:mm:ss.SSS");
Date date = formatter.parse(eventDate);
long modifiedDate= date.getTime();
if (dateNow.compareTo(modifiedDate)>0) {
//Do Something
}
Error I get is :
Cannot invoke compareTo(long) on the primitive type long
Thanks.

When comparing primitive longs just use a vanilla comparison operator:
dateNow > modifiedDate
This is not recommended, but if you want to use compareTo, first convert to Long:
Long.valueOf(dateNow).compareTo(Long.valueOf(modifiedDate)) > 0

compareTo method is part of wrapper classes, long is primitive datatype - you cannot call method on primitive datatype. Either change long to Long or compare long directly like dateNow > modifiedDate

long is a primitive type, which means it is not an object and doesn't have basic methods like compareTo, etc. You can perform mathematical operations to compare them though:
if (dateNow - modifiedDate > 0) /* dateNow is later than modifiedDate */
Another solution is using Long (capital L) which is an object. Then you can use compareTo, etc.

compareTo is a method. It is not defined for the primitive type long. It is defined for the Date class.
Date dateNow = currentDate.getTime(); // instead of getTimeInMillis()
...
if (dateNow.compareTo(date)) { // this will now work
If they're both Date objects, you can do dateNow.before(date) which makes much more sense semantically.
Alternatively, you can use the > and < operators and do dateNow < modifiedDate if you leave dateNow as a long.