If CarA is orphan but still in the JVM due to undetermined garbage collector behavior, do you still want Thread2 detects it?
-yuanzidan(原子弹);
2006-3-21(#2856226@0)
No. What I need is, for Thread 2, find out whether CarA is being invoked by another thread.
-sailor(送你一朵西兰花);
2006-3-21(#2856249@0)
is there any way to access JVM's heap or something like that?
-objectspace(New File Sys);
2006-3-21(#2856261@0)
One of CarA's method is being called by another thread not nesessay thread1? how about you make CarA a monitor, in thread2 check holdslock?
-yuanzidan(原子弹);
2006-3-21(#2856332@0)
does Java support such low level object recognization? I dont know Java well, maybe some kind reflection may help. Does Java support this?
-objectspace(New File Sys);
2006-3-21(#2856254@0)
可以搞一个pool池, 或者类似的做法, thread create carA 后,把carA放入一个collection中
-guoluworker(锅炉工);
2006-3-21(#2856267@0)
why not singleton? when count goes down to 0, force GC.
-objectspace(New File Sys);
2006-3-21(#2856333@0)
if you read the code for JDK implementation, System.gc() does not do the garbage collection any more
-blackscraper(橡皮鱼);
2006-3-21{161}(#2856513@0)
JDK with version higher than 1.1 NEVER EVER guarantees the call into System.gc() tiggers the garbage collection. In fact, you can NOT force a garbage collection.
Use pool with weak reference.
-ra_95(凡信的,都将归于荣耀);
2006-3-21(#2856417@0)
support this one
-informix(informix);
2006-3-21(#2856472@0)
Thanks~~~ I believe this is the correct direction.
-sailor(送你一朵西兰花);
2006-3-21(#2856479@0)
if u dont care about life time, and dont want to reuse it, how about use a global counter, add code in ctor, that's it. not OO approach though.
-objectspace(New File Sys);
2006-3-21(#2856496@0)
if you want to know excat how many, use finalize ()
-objectspace(New File Sys);
2006-3-21(#2856506@0)
No wonder you cannot beat a "造假人士" ... lol ... 如果你到我这面食，你肯定不过...随便找个retraining的都比你强太多。找不到工作的，要么象你，要么就是太老实。对了，我就是一个靠假简历改行的，大家认识一下。LOL.....
-ra_95(凡信的,都将归于荣耀);
2006-3-21(#2856515@0)
haha, before u LOL... according to his original requirement, he only wants to know at a certain time, how many Cars are created.
-objectspace(New File Sys);
2006-3-21{128}(#2856531@0)
He event does not care about whether afterwards, the existing car will disappear. what's use for your pool though in this case?
/**
* Factory to generate weak referenced singleton instances. <p/> Sample Usage:
*
* <pre>
* class ClassA {
* //contents here
* }
*
* class UserClass {
* public void classAUser() {
* ClassA classA = (CarA) SingletonFactory.getInstance()
* .getSingletonInstanceOf(ClassA.class);
* }
* }
* </pre>
*
* @see java.lang.ref
* @see java.util.WeakHashmap
*
*/ public class SingletonFactory { private static Log log = LogFactory.getLog(SingletonFactory.class); private static Map map = new WeakHashMap(); private static SingletonFactory instance = new SingletonFactory();
private SingletonFactory() {
//intended
}
/**
* @return instance of SingletonFacotry
*/ public static SingletonFactory getInstance() { return instance;
}
/**
* Synchronzied method to instantiate object or get if exist.
*
* @param clazz Class for which to get instance. The method uses reflection
* to instantiate the class, so clazz should have a default
* constructor accessable by this factory.
* @return Instance generated or got from registry
* @see java.lang.Reflection
*/ public synchronized// TODO could use volatile and/or Semaphore to improve
// performance in JDK5.0+
Object getSingletonInstanceOf(Class clazz) {
if (null == clazz) throw new IllegalArgumentException("need a valid Class");
Object object = map.get(clazz.getName()); if (null == object) { try {
object = clazz.newInstance();
} catch (InstantiationException e) {
log.fatal("cannot instantiate Class " + clazz.getName()); throw new RuntimeException(e);
} catch (IllegalAccessException e) {
log.fatal("illegal access to Class " + clazz.getName()); throw new RuntimeException(e);
}
map.put(clazz.getName(), object);
log.debug("new object of " + clazz.getName() + "created");
} return object;
}
}