什么时候执行一个类的静态块?

When is the static block of a class executed?(什么时候执行一个类的静态块?)

问题描述

我有 2 个罐子，我们称它们为 a.jar 和 b.jar.

I have 2 jars, let's call them a.jar and b.jar.

b.jar 依赖于 a.jar.

b.jar depends on a.jar.

在一个.jar 中，我定义了一个类，我们称之为StaticClass.在 StaticClass 中，我定义了一个静态块，调用了一个名为init"的方法:

In a.jar, I defined a class, let's call it StaticClass. In the StaticClass, I defined a static block, calling a method named "init" :

public class StaticClass {
  static {
    init();
  } 

  public void static init () {
    // do some initialization here
  }
}

在 b.jar 中，我有一个 main，所以在 main 中，我希望 init() 方法已被调用，但实际上没有.我怀疑这是因为 jvm 没有加载 StaticClass，谁能告诉我

in b.jar, I have a main, so in the main, I expect that the init() method has been called, but actually not. I suspect that is because the StaticClass has not been loaded by the jvm, could anyone tell me

1. 我的结论正确吗?
2. 什么触发 jvm 加载类?
3. 如何让静态块自动执行?

谢谢

推荐答案

是的，你是对的.静态初始化块在 JVM(具体来说是类加载器)加载 StaticClass(在代码中第一次引用它时发生)时运行.

Yes, you are right. Static initialization blocks are run when the JVM (class loader - to be specific) loads StaticClass (which occurs the first time it is referenced in code).

您可以通过显式调用 StaticClass.init() 来强制调用此方法，这比依赖 JVM 更可取.

You could force this method to be invoked by explicitly calling StaticClass.init() which is preferable to relying on the JVM.

您也可以尝试使用 Class.forName(String) 来强制 JVM 加载该类并调用其静态块.

You could also try using Class.forName(String) to force the JVM to load the class and invoke its static blocks.

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