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），他們必須相應地執行。但是這些線程中沒有一個能夠獲得更新的靜態變量數據，除了每個維護靜態變量的狀態之外。

我已經將靜態變量放在一個單例中，並將其聲明爲volatile，但結果仍然相同。

有人可以提出這種方法的問題，以及可以做些什麼來解決這個問題。

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

聲明你的參考單揮發性是不會幫助，如果你打算髮生變異的狀態。你需要用揮發性變種要麼使用簡稱的不變單，或使在單揮發性每一個人變種。只有在你沒有原子性問題的情況下。第二種方法幾乎與沒有單身人士相同，只是一些static volatile全局變量。