Hello,
I was unable to get the date/time information consistently.
Exe 1.3:
**********************************************************************
Date d1 = new Date();
for (int i=0; i<10000000; i++) { int j = i;}
Date d2 = new Date();
long elapsed_time = d2.getTime() - d1.getTime();
System.out.println("That took " + elapsed_time
+ " milliseconds");
}
**********************************************************************
I will normally get d2.getTime() - d1.getTime() = 0
But if I ran it again, it will be able to get the time different.
Exe 3.1
********************************************************************************************
import java.io.*;
class SystemDemo {
public static void main(String args[]) throws IOException {
int arr1[] = new int[1050000];
int arr2[] = new int[1050000];
long startTime, endTime;
/* initialize arr1 */
for (int i = 0; i < arr1.length; i++) {
arr1[i] = i + 1;
}
/* copying manually */
startTime = System.currentTimeMillis();
System.out.println("start time: " + startTime + " ms.");
for (int i = 0; i < arr1.length; i++) {
arr2[i] = arr1[i];
}
endTime = System.currentTimeMillis();
System.out.println("end time: " + endTime + " ms.");
System.out.println("Time for manual copy: " + (endTime-startTime) + "
ms.");
/* using the copy utility provided by java */
startTime = System.currentTimeMillis();
System.out.println("start time: " + startTime + " ms.");
System.arraycopy(arr1, 0, arr2, 0, arr1.length);
endTime = System.currentTimeMillis();
System.out.println("end time: " + endTime + " ms.");
System.out.println("Time when using method of array copy: " +
(endTime-startTime) + " ms.");
System.gc(); //force garbage collector to work
//System.setIn(new FileInputStream("temp.txt"));
System.exit(0);
}
}
***********************************************************************************************************
Sometime I get Time for manual copy and array copy = 0ms;
But I can only get the manual copy time = 15ms but array copy time
still 0ms after few run.
If i try to debug the code by inserting a System.out.println
(startTime), I might get the result the other way around.
which is manual copy time = 0ms and array copy time = 15ms.
Pls help... I'm not sure what is causing this strange behavior.
BestRegards,
YH
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