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Thread: Difference in time with alternative methods

  1. #1
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    Default Difference in time with alternative methods

    Hi all,

    I'm not looking for the answer but rather a point in the right direction would be most welcome.

    I have used two methods to tell the current time from System.currentTimeMillis()

    The first method using the java.util.Date gives me the correct time, but the second method (using long calculation) gives me the time - 1 hour. e.g: util.Date giving 9:30am and the long method giving 8:30am

    I can't figure out why the two times would be different.

    Any and all advice welcome.

    Code below:

    import java.util.Date;
    class Q8
    {
    public static void main (String[]args)
    {
    long currentMillisecond = System.currentTimeMillis();
    Date currentDate = new Date(currentMillisecond);
    System.out.println("The current date is: " + currentDate);

    long seconds = currentMillisecond/1000;
    long currentSecond = seconds%60;

    long minutes = seconds/60;
    long currentMinute = minutes%60;

    long hours = minutes/60;
    long currentHour = hours%24;

    System.out.println("The current time is: " + currentHour + ":" + currentMinute + ":" + currentSecond);
    }
    }


  2. #2
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    Default Re: Difference in time with alternative methods

    First of all System.currentTimeMillis() is based on your chip time, which is NOT the time your clock is.
    Second of all I can pin point it but something in the calculations seems wrong to me.
    Third of all NEVER EVER user numbers in your class names. I know it is not your question, but it is bad conduct.
    Fourth of all I have run this on 3 different chipsets now and I get 3 different outputs, so I suspects it has something to do with number one,
    read about the currentTimeMillis here: System (Java Platform SE 7 )
    Ruby 'cause I can - Java 'cause I want - C# 'cause I have to

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    Default Re: Difference in time with alternative methods

    As tools has pointed out, currentTimeMillis() does not take into account your local clock at all, only the unix epoch time since January 1970. This fact is also true for the Date object internal timing. However, the toString() method for Date does use your local time, but no other part of it does. This is typically a great source for confusion. If you want your local date in milliseconds, I suggest you use:

    Calendar.getInstance(TimeZone.getDefault()).getTimeInMillis();
    Please use [highlight=Java]//code goes here...[/highlight] tags when posting your code

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    Default Re: Difference in time with alternative methods

    Thanks all.

    1: The only reason i set a class with a number is that is what is being asked of me by my lecturer. e.g: questions 1-9, name the programs and classes within as q1 q2 q3 etc.
    2: Why is this bad practice? Far as i can tell, there is no universally agreed naming convention, so i would leave good/bad practice to the decision of the employer surely?
    3: is there any way to force java to take daylight savings into account when using the long calculation method?

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    Default Re: Difference in time with alternative methods

    1. Fair and square
    2. I have always been told it both by Lectures, my employers and the dude from Oracle who taugth my class once
    Ruby 'cause I can - Java 'cause I want - C# 'cause I have to

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    Default Re: Difference in time with alternative methods

    Quote Originally Posted by CruelCoin View Post
    Far as i can tell, there is no universally agreed naming convention
    Yes there is. See Code Conventions for the Java Programming Language

    Quote Originally Posted by CruelCoin View Post
    3: is there any way to force java to take daylight savings into account when using the long calculation method?
    See TimeZone (Java Platform SE 7 )

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    Default Re: Difference in time with alternative methods


    Thanks! i have posted that convention link to my student group.

    Cheers,

    CC.

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