Java静态初始化器线程安全吗?

织梦狗教程 Java问题

2022-01-01

Are Java static initializers thread safe?(Java静态初始化器线程安全吗?)

本文介绍了Java静态初始化器线程安全吗?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

I'm using a static code block to initialize some controllers in a registry I have. My question is therefore, can I guarantee that this static code block will only absolutely be called once when the class is first loaded? I understand I cannot guarantee when this code block will be called, I'm guessing its when the Classloader first loads it. I realize I could synchronize on the class in the static code block, but my guess is this is actually what happens anyway?

Simple code example would be;

class FooRegistry {

    static {
        //this code must only ever be called once 
        addController(new FooControllerImpl());
    }

    private static void addController(IFooController controller) { 
        // ...
    }
}

or should I do this;

class FooRegistry {

    static {
        synchronized(FooRegistry.class) {
            addController(new FooControllerImpl());
        }
    }

    private static void addController(IFooController controller) {
        // ...
    }
}

解决方案

Yes, Java static initializers are thread safe (use your first option).

However, if you want to ensure that the code is executed exactly once you need to make sure that the class is only loaded by a single class-loader. Static initialization is performed once per class-loader.

这篇关于Java静态初始化器线程安全吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！

线程