Thread: HELP "code needed"

Hello

Can someone please show me code in Java that stores the date and time into a file every minute?
The reason for this is that i am looking to copy every minute from the computer clock in order to see if changes have been made.

I am not sure if I need to use a loop of some sort or whether there is code itself that will do this for me.

Any help will be appreciated

Thanks
Dave

Welcome to Java Programming Forums Dave.

Well lets see what you have as a starter, so we have a place to build off. A loop will be needed to make it run yes Thread.sleep() may also be helpful in timing, or you could use System timing if you wish to be more accurate.

Chris

Thank you very much for the help

i do have a couple of extra issues/ help with this

1. will this coinside with the computer. if not how can i make this happen as this is really important

2. i am also looking at adding a method that will not allow you to change the clock by more than 5 mins at a time. This is why i need the recordings to coincide with the computer clock. Also if it is possible i would like to add a rule that will allow the clock to change when the clocks naturally move forward or back (GMT)

finally i am looking to add a password box in order to end the program and also ideally a password box that needs to be typed when i call for the list of times.

I know this sounds like i am throwing alot out there however i am researching to see if java can be used as a computer clock monitor as part of a computer forensics research.

Once again any help will be appreciated.

Thankyou

Dave

Originally Posted by Dave

i do have a couple of extra issues/ help with this

1. will this coinside with the computer. if not how can i make this happen as this is really important

2. i am also looking at adding a method that will not allow you to change the clock by more than 5 mins at a time. This is why i need the recordings to coincide with the computer clock. Also if it is possible i would like to add a rule that will allow the clock to change when the clocks naturally move forward or back (GMT)

finally i am looking to add a password box in order to end the program and also ideally a password box that needs to be typed when i call for the list of times.

I know this sounds like i am throwing alot out there however i am researching to see if java can be used as a computer clock monitor as part of a computer forensics research.

Once again any help will be appreciated.

Thankyou

Dave

This is a very interresting question. It can probably be pulled of, but it will need some hardcore coding, beyond what java is capable of(if what I understanding from your questions is correct that is.)
Im hoping one the sharp minds will look this over, and either correct me if im wrong, or show some magic.

1. The Calendar gives you the time read of the computer clock, everytime you make a new instance. In other words, change the computer clock, changes the println respectivly.

2. Here is what i understand. You want to "fix" your computer clock, so it cant be modified with more than x on one change. If that is the case, it cant be solved by java, atleast not java alone. Your clock i run in the os.
Java is run in a virtual mashine (jvm), which isolates it from its environment (memory, os etc). Contact in and out of the jvm is tricky at best, impossible at worst. There is a framework(Java Native Interface) specializing in exactly this, but other than knowing how to use it, you also need to have a very good understanding of your os, to manipulate it in a way like this.
In windows you can change pretty much anything if you know how, dont know to much about different linux destros, but im guessing its the same.

3. If by password you mean "cant shut down the program without it" then no, cant be done in java (read 2).

Ye, Java cannot interact with the clock to the level that you wish as stated by Johannes. But he is correct, JNI (Java Native Interface) wil allow you to communicate with C or C++ which can then work nicely with system operations and can do that sort of thing. Again you cannot stop the user from closing the program down as they can get at it from a system level. But once again JNI and C or C++ can be used to deal with this. If you are prepared to learn how to use the JNI and C or C++ if you are not already familiar then you are ok. Ofcourse since you are investigating if Java alone can do it then I have to say no.

Also if you inlist the aid of C or C++ and system functions, you have just lost portability.

Chris,
This reminds me, I have a Mouse/Keyboard hook to finish writing in C++ using JNI D:

Never, never use Thread.Sleep() you will end up totally wrong. It waits more than given time and it can wait lot longer when your processor cycles are sucked by some other process. Look at this as well: Thread (Java 2 Platform SE v1.4.2), int)

In fact I would rather suggest Timer, but never sleep. You should look here: Timer Schedule a task that executes once every second : TimerDevelopment ClassJava

Also I posted 'DateTime is not thread safe' in tips section yesterday, please try to use joda time. I know you are just starting, but these are some good practices.

Will try to post more when I am free. Good luck.

Acumen,
Lucid forums

Actually there are a number of ways to set the system time using Java, I had a discussion about this with a colleague a while back.

1. Write or download a library for this with including native library files such as .dll .so etc. This will be limited to the operating system you have the native libraries for.

2. Use Java runtime to set the time using a call to the operating system command, for instance in Windows XP you could use time

        try {
            Runtime.getRuntime().exec("time 12:00");
        } catch (IOException e) {
            e.printStackTrace();
        }

You would of course have to write some code to check what operating system the program is run to select the correct command.

// Json

Thank you Json

my java skills arnt the greatest. how would i actually do this

Either by using that code snippet I gave you in my previous post or you could try and find a sort of Java time library with natives for it or was your question regarding something else?

// Json

ok 1 last question

with the code supplied by JavaPF I am looking at adding a method or something that will warn the user if there has been a sudden change of 5 minutes or more, this can be done as an error message.

Once again thanks for all the help.

Dave