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Java: Something is getting lost when += is applied

This is my code, but its output does make any sense.
long currentTime;
long stateStartTime;
int delta;
float speed;
// I do something
System.out.println();
System.out.println(currentTime);
System.out.println(stateStartTime);
System.out.println(delta);
System.out.println(speed);
System.out.println(delta * speed);
System.out.println(currentTime - (stateStartTime + (delta * speed)));
stateStartTime += delta * speed;
System.out.println(currentTime - stateStartTime);
Output:
1350065634345877
1350065121656832
1
5.0E8
5.0E8
0.0
-24181867
I was expecting the last two rows to be:
12689045
12689045
But surprisingly I got the above result. Why?

Don't drop precision and expect the computer to re-create it.
long currentTime = 1350065634345877L;
long stateStartTime = 1350065121656832L;
long delta = 1L;
double speed = 5.0E8;
And your last two lines (with no other changes) output
1.2689045E7
12689045
To make the penultimate line match the final line, you could use a BigDecimal like
System.out.println(new BigDecimal(currentTime - (stateStartTime + (delta * speed)))
.toPlainString());

Convert Days to hours:minutes:second java

How can I convert 0.230324074074074 to 05:31:40 in Java? I have code in sql but need in java.
(select * from(SELECT TRUNC (
( (X_GSA_LEAVE_SITE - X_GSA_ARRIVE_ONSITE)
* 24
* 60)
/ 60)
|| ':'
|| ( ( (X_GSA_LEAVE_SITE - X_GSA_ARRIVE_ONSITE)
* 24
* 60)
- TRUNC (
( ( X_GSA_LEAVE_SITE
- X_GSA_ARRIVE_ONSITE)
* 24
* 60)
/ 60)
* 60)

It appears that the value 0.230324 is a fraction of a day, and you want to display this as hours:minutes:seconds. There is a fairly straightforward way to do this in Java 8:
double input = 0.230324074074074d;
long seconds = new Double(input*24*60*60).longValue();
System.out.println(LocalTime.MIN.plusSeconds(seconds)
.format(DateTimeFormatter.ISO_LOCAL_TIME));
05:31:39
Demo

You can convert that fraction of day to a LocalTime using:
LocalTime.ofSecondOfDay((long)(0.230324074074074 * 24 * 60 * 60))
This converts the value to seconds and constructs a LocalTime object. Printing the result outputs "05:31:39" (LocalTime.toString outputs time in your desired format). You may need to control rounding in a different way if you expect exactly 05:31:40)

Just for fun here is an old fashioned Calendar version
int seconds = (int) (0.230324074074074 * 24 * 60 * 60);
Calendar cal = Calendar.getInstance();
cal.set(Calendar.HOUR, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.add(Calendar.SECOND, seconds);
String result = String.format("%02d:%02d:%02d",
cal.get(Calendar.HOUR),
cal.get(Calendar.MINUTE),
cal.get(Calendar.SECOND));
System.out.println(result);

long seconds = (long) (0.230324074074074 * 24 * 60 * 60);
String result = String.format("%02d:%02d:%02d", seconds / 3600, (seconds % 3600) / 60, (seconds % 60));
System.out.println(result);

Fixing game loop to 60fps makes animation very jittery

ns is 1000000000 / amountOfTicks;
long now = System.nanoTime();
delta += (now - lastTime) / ns;
lastTime = now;
if (delta >= 1) {
tick(glad);
updates++;
delta--;
fps_counter = 0;
}
if (delta >= fps_counter / FramesPerTick) { // render
fps_counter++;
frames++;
render(glad);
}
if (System.currentTimeMillis() - timer > 1000) {
timer += 1000;
frame.setTitle("Ticks: " + updates + " Fps: " + frames);
updates = 0;
frames = 0;
}
So if i have 20 ticks and 3 FramesPerTick i get 60fps
it checks whenever delta is bigger than 1/3, 2/3 and 3/3, so every tick has 3 frames
Everything is jittery, movement, mouse look.
Animation gets more and more jittery the lower the FPS, i dont understand why.
Also when i take the render(glad) method out of the if, it goes up to 400 fps and runs very smoothly.

Can't get count down timer to have 100th of seconds

I have a count down timer that works fine except for I'm geting numbers that have more then 2 digits for the 100th of seconds. I'm creating 2 calendar objects, bgetting there time alue in milli secons, and subtracting it. code
long milsecs1= calendar1.getTimeInMillis();
long milsecs2 = calendar2.getTimeInMillis();
long diff = milsecs2 - milsecs1;
long dsecs = diff / 1000;
long ddays = diff / (24 * 60 * 60 * 1000);
diff=diff-ddays *(24 * 60 * 60 * 1000);
textDays.setText( Integer.toString( (int)ddays)+":" );
long dhours = diff / (60 * 60 * 1000);
diff=diff-dhours* (60 * 60 * 1000);
textHours.setText( Integer.toString( (int)dhours)+":" );
long dminutes = diff / (60 * 1000);
diff=diff-dminutes* (60 * 1000);
textMinuts.setText( Integer.toString( (int)dminutes)+":" );
/////////////////////////////////////////////////
// THIS IS THE PART THAT IS NOT WORKING, I WANT NUMBERS 0-99, BUT GETTING NUMBERS LIKE 230
long dseconds = diff / (100);
textSeconds.setText( Integer.toString( (int)dseconds)+":" );
diff=diff-dseconds;

Joda time provides a much simpler (and thoroughly proven) solution in its Period class. Something like this should do the trick (untested):
Period period = new Period(calendar1.getTimeInMillis(), calendar2.getTimeInMillis());
int days = period.getDays();
int hours = period.getHours();
... etc.

How to display time amount to user?

I want to convert time amount from milli-sec to a human readable string.
For example:
3,600,000 should be displayed as 1:00:00 (1 hour).
Is there an existing library or class in Java that can do that?

Since 1.5 there is the java.util.concurrent.TimeUnit class, use it like this:
String.format("%d min, %d sec",
TimeUnit.MILLISECONDS.toMinutes(millis),
TimeUnit.MILLISECONDS.toSeconds(millis) -
TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(millis))
);
For Versions below 1.5 You have to use
int seconds = (int) (milliseconds / 1000) % 60 ;
int minutes = (int) ((milliseconds / (1000*60)) % 60);
int hours = (int) ((milliseconds / (1000*60*60)) % 24);