Question of System.currentTimeMillis();

Question

Hi there,
I got some problem in method "System.currentTimeMillis()" .
The part of my function is:
     long c= System.currentTimeMillis();
     System.out.println("before time="+c);
          some codes here
try{new Thread().sleep(1000);}catch(Exception e){} //sleep for additional 1 second
     long b= System.currentTimeMillis();
     System.out.println("after time="+b);
     c=c-b;
     System.out.println("run time="+c);
the output is:
     before time=1001526336640
     after time= 1001526345985
     run time= -9345
Couple things I could understand:
1. b and c are long. in Java they are 8 bytes. in C++ LIMITS.H, long is 4 bytes "#define ULONG_MAX 0xffffffffUL /* maximum unsigned long value */"
But why time value shows that huge number?
2. It is strange to get small time after running, the currentTimeMillis() return the difference, measured in milliseconds, between the current time and midnight, January 1, 1970 UTC.
It took me whole day but I couldn't get answer yet. Do you have some idea?
Thanks

Answer 1

Im not quite sure what your asking here ?????
One thing I would like to point out is that you have youre vars a bit mixed in the subtraction
long b= System.currentTimeMillis();
System.out.println("after time="+b);
c=c-b;
System.out.println("run time="+c);should be
c= b-c which would equal:9345
aproximately 9 seconds...
the currentTimeMillis() return the difference, >>measured in milliseconds, between the current time >>and midnight, January 1, 1970 UTC, Im not too sure this is correct the way you have it stated....
Its better stated that currentTimeMillis() returns the number of milliseconds that have elapsed, at this current time, since midnight, January 1, 1970 UTC, which is a rather large number..Do the math if youd like.....
A time yesterday will be smaller than a time today...
Unfortunately you will need to state your question a bit better in order to get an adequate answer, Please do so and Im sure youll get some answers...