How about [`System.currentTimeMillis()`][1]?

From the JavaDoc:

**Returns:** *the difference, measured in milliseconds, between the current time and midnight, January 1, 1970 UTC*

**Java 8** introduces the [`java.time`][2] framework, particularly the [`Instant`][3] class which &quot;*...models a ... point on the time-line...*&quot;:

    long now = Instant.now().toEpochMilli();

**Returns:** *the number of milliseconds since the epoch of 1970-01-01T00:00:00Z* -- i.e. pretty much the same as above :-)

Cheers,


  [1]: http://docs.oracle.com/javase/6/docs/api/java/lang/System.html#currentTimeMillis%28%29
  [2]: https://docs.oracle.com/javase/8/docs/api/java/time/package-summary.html
  [3]: https://docs.oracle.com/javase/8/docs/api/java/time/Instant.html

# java.time

Using the [`java.time`][1] framework built into Java 8 and later.

    import java.time.Instant;

    Instant.now().toEpochMilli(); //Long = 1450879900184
    Instant.now().getEpochSecond(); //Long = 1450879900

This works in UTC because `Instant.now()` is really call to `Clock.systemUTC().instant()`

https://docs.oracle.com/javase/8/docs/api/java/time/Instant.html

  [1]: http://docs.oracle.com/javase/8/docs/api/java/time/package-summary.html

You can also try 

      Calendar calendar = Calendar.getInstance();
      System.out.println(calendar.getTimeInMillis());

getTimeInMillis() - the current time as UTC milliseconds from the epoch

I have been doing some research on this but I am still VERY confused to say the least.

Can anyone give me a concrete example of when to use `Task` and when to use `Platform.runLater(Runnable);`? What exactly is the difference? Is there a golden rule to when to use any of these?

Also correct me if I&#39;m wrong but aren&#39;t these two &quot;Objects&quot; a way of creating another thread inside the main thread in a GUI (used for updating the GUI)?

Platform.runLater and Task in JavaFX

I see some code samples with constructs like this:

    type point struct {
      x, y int
    }

    func newPoint() *point {
      return &amp;point{10, 20}
    }

I have C++ background and it seems like error for me. What are the semantic of such construct? Is new point allocated on the stack or heap?





Return pointer to local struct

I need to get the number of milliseconds from 1970-01-01 UTC until now UTC in Java.

I would also like to be able to get the number of milliseconds from 1970-01-01 UTC to any other UTC date time.

How do I get milliseconds from epoch (1970-01-01) in Java?

<p>I need to get the number of milliseconds from 1970-01-01 UTC until now UTC in Java.</p>
<p>I would also like to be able to get the number of milliseconds from 1970-01-01 UTC to any other UTC date time.</p>


I&#39;m learning Swing class now and everything about it. I&#39;ve got this toy program I&#39;ve been putting together that prompts for a name and then presents a JOptionPane with the message &quot;You&#39;ve entered (Your Name)&quot;.
The submit button I use can only be clicked on, but I&#39;d like to get it to work with the Enter button too. I&#39;ve tried adding a KeyListener, as is recommended in the Java book I&#39;m using (Eventful Java, Bruce Danyluk and Murtagh).

![NamePrompt][1]
![enter image description here][2]


This is my code:

    import java.awt.BorderLayout;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    
    import javax.swing.JButton;
    import javax.swing.JFrame;
    import javax.swing.JLabel;
    import javax.swing.JPanel;
    import javax.swing.JTextField;
    
    
    public class NamePrompt extends JFrame{
    	
    	
    	private static final long serialVersionUID = 1L;
    	
    	String name;
    	
    	public NamePrompt(){
    		
    		setLayout(new BorderLayout());
    		
    		JLabel enterYourName = new JLabel(&quot;Enter Your Name Here:&quot;);
    		JTextField textBoxToEnterName = new JTextField(21);
    		JPanel panelTop = new JPanel();
    		panelTop.add(enterYourName);
    		panelTop.add(textBoxToEnterName);
    		
    		JButton submit = new JButton(&quot;Submit&quot;);
    		submit.addActionListener(new SubmitButton(textBoxToEnterName));
    		submit.addKeyListener(new SubmitButton(textBoxToEnterName));
    		JPanel panelBottom = new JPanel();
    		panelBottom.add(submit);
    		
    		//Add panelTop to JFrame
    		add(panelTop, BorderLayout.NORTH);
    		add(panelBottom, BorderLayout.SOUTH);
    		
    		//JFrame set-up
    		setTitle(&quot;Name Prompt Program&quot;);
    		setDefaultCloseOperation(EXIT_ON_CLOSE);
    		pack();
    		setLocationRelativeTo(null);
    	
    		
    	}
    
    
    	
    	public static void main(String[] args) {
    		NamePrompt promptForName = new NamePrompt();
    		promptForName.setVisible(true);	
    	}
    	
    
    }


And this is the actionListener, keyListener class:

    import java.awt.Component;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.awt.event.KeyEvent;
    import java.awt.event.KeyListener;
    
    import javax.swing.JFrame;
    import javax.swing.JOptionPane;
    import javax.swing.JTextField;
    
    
    public class SubmitButton implements ActionListener, KeyListener {
    
    	JTextField nameInput;
    	
    	
    	public SubmitButton(JTextField textfield){
    		nameInput = textfield;
    	}
    
    	@Override
    	public void actionPerformed(ActionEvent submitClicked) {
    		
    		Component frame = new JFrame();
    		JOptionPane.showMessageDialog(frame , &quot;You&#39;ve Submitted the name &quot; + nameInput.getText());
    	}
    
    	@Override
    	public void keyPressed(KeyEvent e) {
    		if (e.getKeyCode()==KeyEvent.VK_ENTER){
    			System.out.println(&quot;Hello&quot;);
    		}
    		Component frame = new JFrame();
    		JOptionPane.showMessageDialog(frame , &quot;You&#39;ve Submitted the name &quot; + nameInput.getText());
    		
    	}
    
    	@Override
    	public void keyReleased(KeyEvent arg0) {
    		// TODO Auto-generated method stub
    		
    	}
    
    	@Override
    	public void keyTyped(KeyEvent arg0) {
    		
    	}
    }


  [1]: http://i.stack.imgur.com/XNRkS.jpg
  [2]: http://i.stack.imgur.com/wnBkE.jpg

Allowing the &quot;Enter&quot; key to press the submit button, as opposed to only using MouseClick

An interviewer asked me:

*What is `Observer` and `Observable` and when should we use them?*

I wasn&#39;t aware of these terms, so when I got back home and started Googling about `Observer` and `Observable`, I found some points from different resources:

&gt; 1) [`Observable`](https://docs.oracle.com/javase/8/docs/api/java/util/Observable.html) is a class and [`Observer`](https://docs.oracle.com/javase/8/docs/api/java/util/Observer.html) is an interface.
&gt; 
&gt; 2) The `Observable` class maintains a list of `Observer`s.
&gt; 
&gt; 3) When an `Observable` object is updated, it invokes the `update()` method of each of its `Observer`s to notify that, it is changed.

I found this example:

    import java.util.Observable;
    import java.util.Observer;
    
    class MessageBoard extends Observable
    {
        public void changeMessage(String message) 
        {
            setChanged();
            notifyObservers(message);
        }
    }
    
    class Student implements Observer 
    {
        @Override
        public void update(Observable o, Object arg) 
        {
            System.out.println(&quot;Message board changed: &quot; + arg);
        }
    }
    
    public class MessageBoardTest 
    {
        public static void main(String[] args) 
        {
            MessageBoard board = new MessageBoard();
            Student bob = new Student();
            Student joe = new Student();
            board.addObserver(bob);
            board.addObserver(joe);
            board.changeMessage(&quot;More Homework!&quot;);
        }
    }


But I don&#39;t understand why we need `Observer` and `Observable`? What are the `setChanged()` and `notifyObservers(message)` methods for?



When should we use Observer and Observable?

Is it possible to count the number of members using JsonPath?

Using [spring mvc test][1] I&#39;m testing a controller that generates 

    {&quot;foo&quot;: &quot;oof&quot;, &quot;bar&quot;: &quot;rab&quot;}

with

    standaloneSetup(new FooController(fooService)).build()
				.perform(get(&quot;/something&quot;).accept(MediaType.APPLICATION_JSON)).andExpect(status().isOk())
				.andExpect(jsonPath(&quot;$.foo&quot;).value(&quot;oof&quot;))
				.andExpect(jsonPath(&quot;$.bar&quot;).value(&quot;rab&quot;));

I&#39;d like to make sure that no other members are present in the generated json. Hopefully by counting them using jsonPath. Is it possible? Alternate solutions are welcome too.


  [1]: https://github.com/SpringSource/spring-test-mvc

count members with jsonpath?

I have an object called `Person`.

it has several attributes in it;

    int id;
    String name;

i set a person object like `Person p = new Person(1,&quot;Joe&quot;);`.

1.) I need to check if the object is not null; Is the following expression correct;


    if (person == null){
    }

    Or


    if(person.equals(null))

2.) I need to know if the ID contains an Int.


    if(person.getId()==null){} 

But, java doesn&#39;t allow it. How can i do this check ?




How to check if an int is a null

I&#39;m creating a Jersey client for a GET service that has a List as query parameter. According to the [documentation](http://jersey.java.net/nonav/documentation/latest/user-guide.html#d4e247), it&#39;s possible to have a List as a query parameter (this information is also at [@QueryParam](http://jsr311.java.net/nonav/releases/1.1/javax/ws/rs/QueryParam.html) javadoc), check it out: 

&gt; In general the Java type of the method parameter may:
&gt;
&gt; 1. Be a primitive type;
&gt; 2. Have a constructor that accepts a single String argument;
&gt; 3. Have a static method named valueOf or fromString that accepts a single String argument (see, for example, Integer.valueOf(String) and java.util.UUID.fromString(String)); or
&gt; 4. Be List&lt;T&gt;, Set&lt;T&gt; or SortedSet&lt;T&gt;, where T satisfies 2 or 3 above. The resulting collection is read-only.
&gt;
&gt; Sometimes parameters may contain more than one value for the same name. If this is the case then types in 4) may be used to obtain all values.

However, I can&#39;t figure out how to add a List query parameter using Jersey client. 

I understand alternative solutions are: 

 1. Use POST instead of GET; 
 2. Transform the List into a JSON string and pass it to the service. 

The first one is not good, because the proper HTTP verb for the service is GET. It is a data retrieval operation. 

The second will be my option if you can&#39;t help me out. :)

I&#39;m also developing the service, so I may change it as needed. 

Thanks!

**Update**

Client code (using json)

    Client client = Client.create();
    
    WebResource webResource = client.resource(uri.toString());
    
    SearchWrapper sw = new SearchWrapper(termo, pagina, ordenacao, hits, SEARCH_VIEW, navegadores);
    
    MultivaluedMap&lt;String, String&gt; params = new MultivaluedMapImpl();
    params.add(&quot;user&quot;, user.toUpperCase()); 
    params.add(&quot;searchWrapperAsJSON&quot;, (new Gson()).toJson(sw));

    ClientResponse clientResponse = webResource .path(&quot;/listar&quot;)
                                                .queryParams(params)
                                                .header(HttpHeaders.AUTHORIZATION, AuthenticationHelper.getBasicAuthHeader())
                                                .get(ClientResponse.class);

    SearchResultWrapper busca = clientResponse.getEntity(new GenericType&lt;SearchResultWrapper&gt;() {});


Jersey client: How to add a list as query parameter

I&#39;m trying to get a difference between two dates in seconds. The logic would be like this :

 - set an initial date which would be now;
 - set a final date which would be the initial date plus some amount of seconds in future ( let&#39;s say 15 for instance )
 - get the difference between those two ( the amount of seconds )

The reason why I&#39;m doing it it with dates it&#39;s because the final date / time depends on some other variables and it&#39;s never the same ( it depends on how fast a user does something ) and I also store the initial date for other things.

I&#39;ve been trying something like this : 

    var _initial = new Date(),
		_initial = _initial.setDate(_initial.getDate()),
		_final = new Date(_initial);
		_final = _final.setDate(_final.getDate() + 15 / 1000 * 60);

    var dif = Math.round((_final - _initial) / (1000 * 60));

The thing is that I never get the right difference. I tried dividing by `24 * 60` which would leave me with the seconds, but I never get it right. So what is it wrong with my logic ? I might be making some stupid mistake as it&#39;s quite late, but it bothers me that I cannot get it to work :)

Get time difference between two dates in seconds

I&#39;m trying to calculate a person&#39;s age using [Moment.js](http://momentjs.com/), but I&#39;m finding that the otherwise useful [fromNow](http://momentjs.com/docs/#/displaying/fromnow/) method rounds up the years. For instance, if today is 12/27/2012 and the person&#39;s birth date is 02/26/1978, `moment(&quot;02/26/1978&quot;, &quot;MM/DD/YYYY&quot;).fromNow()` returns &#39;35 years ago&#39;. How can I make Moment.js ignore the number of months, and simply return the number of years (i.e. 34) since the date?

Moment.js - how do I get the number of years since a date, not rounded up?

I have to store UTC dateTime in DB.&lt;BR&gt;
I have converted the dateTime given in specific timezone to UTC. for that I followed the below code.&lt;BR&gt;
My input dateTime is &quot;20121225 10:00:00 Z&quot; timezone is &quot;Asia/Calcutta&quot; &lt;BR&gt;
My Server/DB(oracle) is running in the same timezone(IST) &quot;Asia/Calcutta&quot; &lt;BR&gt;


**Get the Date object in this specific Timezone**

            String date = &quot;20121225 10:00:00 Z&quot;;
            String timeZoneId = &quot;Asia/Calcutta&quot;;
            TimeZone timeZone = TimeZone.getTimeZone(timeZoneId);

			DateFormat dateFormatLocal = new SimpleDateFormat(&quot;yyyyMMdd HH:mm:ss z&quot;);
                        //This date object is given time and given timezone
			java.util.Date parsedDate = dateFormatLocal.parse(date + &quot; &quot;  
							 + timeZone.getDisplayName(false, TimeZone.SHORT));

			if (timeZone.inDaylightTime(parsedDate)) {
				// We need to re-parse because we don&#39;t know if the date
				// is DST until it is parsed...
				parsedDate = dateFormatLocal.parse(date + &quot; &quot;
						+ timeZone.getDisplayName(true, TimeZone.SHORT));
			}
            
           //assigning to the java.sql.TimeStamp instace variable
            obj.setTsSchedStartTime(new java.sql.Timestamp(parsedDate.getTime()));

**Store into DB**

            if (tsSchedStartTime != null) {
                stmt.setTimestamp(11, tsSchedStartTime);
            } else {
                stmt.setNull(11, java.sql.Types.DATE);
            }
**OUTPUT**

DB (oracle) has stored the same given `dateTime: &quot;20121225 10:00:00` not in UTC.

I have confirmed from the below sql.

         select to_char(sched_start_time, &#39;yyyy/mm/dd hh24:mi:ss&#39;) from myTable

My DB server also running on the same timezone &quot;Asia/Calcutta&quot;

It gives me the below appearances 

1. `Date.getTime()` is not in UTC 
2. Or Timestamp is has timezone impact while storing into DB
What am I doing wrong here?

**One more question:**

Will `timeStamp.toString()` print in local timezone like `java.util.date` does? Not UTC?

Is java.sql.Timestamp timezone specific?

I have a table which contains a datetime column.  I wish to return all records of a given day regardless of the time.  Or in other words, if my table only contained the following 4 records, then only the 2nd and 3rd would be returned if I limit to 2012-12-25.

    2012-12-24 00:00:00
    2012-12-25 00:00:00
    2012-12-25 06:00:00
    2012-12-26 05:00:00

MySQL SELECT WHERE datetime matches day (and not necessarily time)

I have a query like this that nicely generates a series of dates between 2 given dates:

    select date &#39;2004-03-07&#39; + j - i as AllDate 
    from generate_series(0, extract(doy from date &#39;2004-03-07&#39;)::int - 1) as i,
         generate_series(0, extract(doy from date &#39;2004-08-16&#39;)::int - 1) as j

It generates 162 dates between `2004-03-07` and `2004-08-16` and this what I want. The problem with this code is that it wouldn&#39;t give the right answer when the two dates are from different years, for example when I try `2007-02-01` and `2008-04-01`.

Is there a better solution?


Content Type	Original Author	Original Content on Stackoverflow
Question	PaulG	View Question on Stackoverflow
Solution 1 - Java	Anders R. Bystrup	View Answer on Stackoverflow
Solution 2 - Java	Przemek	View Answer on Stackoverflow
Solution 3 - Java	Alexander Pavlov	View Answer on Stackoverflow
Solution 4 - Java	Hari Rao	View Answer on Stackoverflow

How do I get milliseconds from epoch (1970-01-01) in Java?

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

java.time

Solution 3 - Java

Solution 4 - Java

Return pointer to local struct

Platform.runLater and Task in JavaFX

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