如何確保使用多個對象的多個線程可以訪問互斥的代碼部分

Question

我有一種方法，一次只能由一個線程訪問。即使線程使用不同的對象，一次只能有一個線程訪問該方法。

我可以在Java中使用什麼來實現這一目標？ 我認爲'synchronized'關鍵字將允許多個線程一次訪問該方法，如果他們使用不同的對象。 我相信與重入鎖相同。

Answer 1

這裏有一些變化。如果我理解了這個問題，我認爲你正在尋找＃5。

// 1. Static method 
public static synchronized void doSomething() { 
    // Mutually exclusive for all calls 
} 

// 2. Static w/ Shared lock 
private static Object STATIC_LOCK = new Object(); 

public static void staticMethod1() { 
    synchronized (STATIC_LOCK) { 
     // Mutually exclusive across staticMethod1() and staticMethod2() 
    } 
} 

public static void staticMethod2() { 
    synchronized (STATIC_LOCK) { 
     // Mutually exclusive across staticMethod1() and staticMethod2() 
    } 
} 

// 3. Instance method 
public synchronized void doSomethingElse() { 
    // Mutually exclusive per instance of class 
} 

// 4. Instance w/ Shared lock 
private Object lock = new Object(); 

public static void method1() { 
    synchronized (lock) { 
     // Mutually exclusive across method1() and method2() for each class instance 
    } 
} 

public static void method2() { 
    synchronized (lock) { 
     // Mutually exclusive across method1() and method2() for each class instance 
    } 
} 

// 5. Instance method synchronization across multiple class instances 
private static Object SHARED_LOCK = new Object(); 

public void commonInstanceMethod() { 
    synchronized (SHARED_LOCK) { 
     // Mutually exclusive across all class instances 
    } 
}