Java中哪些情况需要同步方法访问? [英] What Cases Require Synchronized Method Access in Java?

问题描述

在什么情况下需要同步对实例成员的访问?我知道对类的静态成员的访问总是需要同步 - 因为它们在类的所有对象实例之间共享.

In what cases is it necessary to synchronize access to instance members? I understand that access to static members of a class always needs to be synchronized- because they are shared across all object instances of the class.

我的问题是，如果我不同步实例成员，我什么时候会出错?

My question is when would I be incorrect if I do not synchronize instance members?

例如，如果我的班级是

public class MyClass {
    private int instanceVar = 0;

    public setInstanceVar()
    {
        instanceVar++;
    }

    public getInstanceVar()
    {
        return instanceVar;
    }
}

在什么情况下(使用类MyClass)我需要有方法:public synchronized setInstanceVar() 和公共同步 getInstanceVar() ?

in what cases (of usage of the class MyClass) would I need to have methods: public synchronized setInstanceVar() and public synchronized getInstanceVar() ?

提前感谢您的回答.

推荐答案

这取决于你是否希望你的类是线程安全的.大多数类不应该是线程安全的(为简单起见)，在这种情况下您不需要同步.如果您需要它是线程安全的，您应该同步访问或使变量可变.(它避免了其他线程获取陈旧"数据.)

It depends on whether you want your class to be thread-safe. Most classes shouldn't be thread-safe (for simplicity) in which case you don't need synchronization. If you need it to be thread-safe, you should synchronize access or make the variable volatile. (It avoids other threads getting "stale" data.)

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