|
Description
|
java version "1.3.0"
Java (TM) 2 Runtime Environment, Standard Edition (build 1.3.0-C)
Java HotSpot(TM) Client VM (build 1.3.0-C, mixed mode)
Two Problems with activeCount(), i.e. a class methods of java.lang.Thread
-------------------------------------------------------------------------
According to the "JavaTM 2 Platform, Standard Edition, v 1.3 - API
Specification":
- activeCount() returns the current number of ACTIVE threads in this thread's
thread group;
- enumerate() copies into the specified array every ACTIVE thread in this
thread's thread group and its subgroups, and returns the number of threads put
into the array.
Problem 1: activeCount() returns MORE than the number of active threads, i.e.
it returns the TOTAL number of ALL threads, including the threads that have not
been started yet!
Problem 2: sometimes(?), activeCount() even returns a wrong value, i.e. a
number EXCEEDING the total number of all threads!
The following application illustrates these two problems:
class MyClass extends Thread {
static boolean stopThread = false;
static void main(String args[]) {
// part 1:
int t = activeCount();
Thread[] threadList = new Thread[10];
int a = enumerate(threadList);
System.out.println("(1) TOTAL # of threads = " + t
+ ", # of ACTIVE threads = " + a + ",\n thread names =");
for (int i = 0; i < a; i++) {
System.out.println(" " + (i+1) + ": " + threadList[i].getName());
}
// part 2:
MyClass threadDriver = new MyClass();
Thread t1 = new Thread(threadDriver);
Thread t2 = new Thread(threadDriver);
t = activeCount();
a = enumerate(threadList);
System.out.println("(2) TOTAL # of threads = " + t
+ ", # of ACTIVE threads = " + a + ",\n thread names =");
for (int i = 0; i < a; i++) {
System.out.println(" " + (i+1) + ": " + threadList[i].getName());
}
// part 3:
t1.start();
t2.start();
t = activeCount();
a = enumerate(threadList);
System.out.println("(3) TOTAL # of threads = " + t
+ ", # of ACTIVE threads = " + a + ",\n thread names =");
for (int i = 0; i < a; i++) {
System.out.println(" " + (i+1) + ": " + threadList[i].getName());
}
// end:
stopThread = true;
}
public void run() {
while (!stopThread) {
}
}
}
The program has been compiled and executed on Windows NT Version 4.0 and on
Windows 95 OEM Service Release 2, using the Java 2 SDK 1.3 for customer
Windows 95/98/NT.
On both platforms the programs displays:
(1) TOTAL # of threads = 3, # of ACTIVE threads = 3,
thread names =
1: main
2: SymcJIT-LazyCompilation-0
3: SymcJIT-LazyCompilation-PA
(2) TOTAL # of threads = 6, # of ACTIVE threads = 3,
thread names =
1: main
2: SymcJIT-LazyCompilation-0
3: SymcJIT-LazyCompilation-PA
(3) TOTAL # of threads = 6, # of ACTIVE threads = 5,
thread names =
1: main
2: SymcJIT-LazyCompilation-0
3: SymcJIT-LazyCompilation-PA
4: Thread-1
5: Thread-2
Output (1): O.K.
Output (2): activeCount() returns 6 (instead of 3) !!!
Output (3): activeCount() returns 6 (instead of 5) !!!
I encountered the same two problems when using the Java 2 SDK 1.2 for customer
Windows 95/98/NT.
(Review ID: 116515)
======================================================================
Posted Date : 2005-10-24 19:27:38.0
|
