What is a scientific notation and why is double printed in scientific notation in Java?

Question

I use this code:

long elapsedTime = now - lastTime;
delta = ((double) elapsedTime) / 1000000000;
System.out.println(elapsedTime);
System.out.println(delta);

This is my output:

173290
1.7329E-4

This output gives me scientific notation, but I don't know what it is. Can you explain me? And why is double printed in scientific notation?

what is the strange thing which happens? looks normal to me. — Peter Lawrey, May 17 '17 at 13:21
What do you find strange? `1.7329E-4` is `1.7329 x 10 ^-4`, which is `0.00017329` — bradimus, May 17 '17 at 13:22
oooooh. thank you i'm just now familiar with those E stuff. I'm just 13 so i didn't learn about that in school. but even tho i'm not really old i'm good at java trust me — Joza100, May 17 '17 at 13:24
Have a look here: http://stackoverflow.com/questions/16098046/how-to-print-double-value-without-scientific-notation-using-java — Oneiros, May 17 '17 at 13:24
the problem now is... when i try to add 1*delta to my X of the play it stays at the same place — Joza100, May 17 '17 at 13:26
See https://en.wikipedia.org/wiki/Scientific_notation#E-notation — bradimus, May 17 '17 at 13:26
What is `x` and where do you declare it? How do you check that it stays at 0. Maybe you should include the code for x in your question. — matt, May 17 '17 at 13:33
public void tick(double delta) { x += 1*delta; } public void render(Graphics2D g) { g.drawRect((int)x, 0, 50, 50); } — Joza100, May 17 '17 at 13:35
`int` is a integer or whole number. If you have a fractional number then when you cast it to int, the fraction gets rounded off. Eg. `x += delta` gives you 0.00017 then you do `(int)x` you will be left with zero. — matt, May 17 '17 at 13:37
but it should move at time, as well i have to cast to int to use graphiccs2D — Joza100, May 17 '17 at 13:38
i found the problem..... it was moving to slow to be visible i increased to 10*delta and it works now — Joza100, May 17 '17 at 13:41
The displacement is too small. Start with `x = 0;` and `x+=delta;` the first time you call that, x will be less then 1 so `(int)x` will be zero. After you call that *a lot* x will be greater than one and your box will move. Another thing you can do is make a velocity. `double velocity = 1000` then `x+= delta*velocity`. That way you can change the value of velocity and move faster. — matt, May 17 '17 at 13:41

victorantunes · Accepted Answer · 2017-05-17T13:38:40.573

The output you're seeing is scientific notation.

In Java, double is printed as scientific notation if the magnitude is less than 10^-3 or greater than 10^7.

Double#toString() javadocs

For a magnitude m:

If m is greater than or equal to 10^-3 but less than 10^7, then it is represented as the integer part of m, in decimal form with no leading zeroes, followed by '.' ('\u002E'), followed by one or more decimal digits representing the fractional part of m.
If m is less than 10^-3 or greater than or equal to 10^7, then it is represented in so-called "computerized scientific notation." Let n be the unique integer such that 10^n ≤ m < 10^n+1; then let a be the mathematically exact quotient of m and 10^n so that 1 ≤ a < 10. The magnitude is then represented as the integer part of a, as a single decimal digit, followed by '.' ('\u002E'), followed by decimal digits representing the fractional part of a, followed by the letter 'E' ('\u0045'), followed by a representation of n as a decimal integer, as produced by the method Integer.toString(int).

Since your output of 1.7329E-4 has a magnitude of 10^-4, it falls under the second category, per listed above.

thanks, now i get it. i'll sure have to remember it!! :D – Joza100 May 17 '17 at 13:33 — Joza100, May 17 '17 at 13:33

score 1 · Answer 2 · answered May 17 '17 at 13:28

1

You should consider using the java.util.concurrent.TimeUnit. It's easier to read and less error-sensitive.

TimeUnit.NANOSECONDS.toSeconds(timeInSeconds)

answered May 17 '17 at 13:28

Mathias Pahlen

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What is a scientific notation and why is double printed in scientific notation in Java?

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