Java線程不共享靜態數據

Question

我有兩個線程應該共享靜態變量數據（不是常量），它們必須相應地執行。 但是，除了每個線程保持其自己的靜態變量狀態之外，這些線程均無法獲取更新的靜態變量數據。

我將靜態變量放在一個單例中並聲明為volatile，結果仍然相同。

有人可以建議這種方法的問題，以及可以解決該問題的方法。

Thx，Aj

below is the code

following is the singleton class

***************************************************************************
public class ThreadFinder {

    public static String pageName;//HashMap threadInfo = new HashMap(); //new HashMap();

private static ThreadFinder singletonObject;
/** A private Constructor prevents any other class from instantiating. */
private ThreadFinder () {
    }
public static synchronized ThreadFinder getSingletonObject() {
    if (singletonObject == null) {
        singletonObject = new ThreadFinder();
    }
    return singletonObject;
}
public static synchronized void setPageName(String Name) {

    pageName = Name;
    //return;
}
public static synchronized String getPageName() {

    return pageName;
    //return;
}
public Object clone() throws CloneNotSupportedException {
    throw new CloneNotSupportedException();
}
//public static void main(String args[])
//{
    //ThreadFinder.getSingletonObject().setPageName("IDEN");
    //System.out.println("page name--------->"+ThreadFinder.getSingletonObject().getPageName());
    //ThreadFinder.getSingletonObject().setPageName("THER");
    //System.out.println("page name--------->"+ThreadFinder.getSingletonObject().getPageName());
//}
}

********************************************************************************

from page 1 below code executes and sets the singleton page variable value to "A" and first pollertimer thread uses the page value as A.

m_poller.setModbusMaster(this.m_connection.getModbusMaster());
m_poller.addListener(this);
ThreadFinder.getSingletonObject().setPageName("A");  //Setting the page name here
PollerTimer polerTimerThread = new PollerTimer(period,"A");  // this is thread

*********************************************************************************

from page2 below code executes and sets the singleton page variable value to "B" and second pollertimer thread uses the page value as B.

m_poller.setModbusMaster(this.m_connection.getModbusMaster());
m_poller.addListener(this);
ThreadFinder.getSingletonObject().setPageName("B");  //Setting the page name here
PollerTimer polerTimerThread = new PollerTimer(period,"B");  // this is thread

***********************************************************************************

Now when first pollertimer thread queries page value using getPageName() it is getting value A instead of B, though it was updated to B by the second thread.

Answer 1

如果您打算改變其狀態，則聲明對單例揮發物的引用將無濟於事。 您需要使用由volatile變量引用的不可變單例，或者使該單例中的每個var都可變 。 這只是在您也沒有原子性問題的情況下。 第二種方法幾乎與完全沒有單例相同，只是沒有多個static volatile全局變量。