Its not very object oriented: One reason statics might be considered "evil" by some people is they are contrary the object-oriented paradigm. In particular, it violates the principle that data is encapsulated in objects (that can be extended, information hiding, etc). Statics, in the way you are describing using them, are essentially to use them as a global variable to avoid dealing with issues like scope. However, global variables is one of the defining characteristics of procedural or imperative programming paradigm, not a characteristic of "good" object oriented code. This is not to say the procedural paradigm is bad, but I get the impression your supervisor expects you to be writing "good object oriented code" and you're really wanting to write "good procedural code".

在Java中，当您开始使用静态时，有许多并不总是立即明显的陷阱。例如，如果在同一个VM中运行两个程序副本，它们会共享静态变量的值并混淆彼此的状态吗?或者当你扩展类时会发生什么，你能重写静态成员吗?您的虚拟机内存不足，因为您有疯狂的静态数据，并且内存不能为其他需要的实例对象回收?

Object Lifetime: Additionally, statics have a lifetime that matches the entire runtime of the program. This means, even once you're done using your class, the memory from all those static variables cannot be garbage collected. If, for example, instead, you made your variables non-static, and in your main() function you made a single instance of your class, and then asked your class to execute a particular function 10,000 times, once those 10,000 calls were done, and you delete your references to the single instance, all your static variables could be garbage collected and reused.

防止某些重复使用: 此外，静态方法不能用于实现接口，因此静态方法会阻止某些面向对象的特性的可用性。

Other Options: If efficiency is your primary concern, there might be other better ways to solve the speed problem than considering only the advantage of invocation being usually faster than creation. Consider whether the transient or volatile modifiers are needed anywhere. To preserve the ability to be inlined, a method could be marked as final instead of static. Method parameters and other variables can be marked final to permit certain compiler optimiazations based on assumptions about what can change those variables. An instance object could be reused multiple times rather than creating a new instance each time. There may be compliler optimization switches that should be turned on for the app in general. Perhaps, the design should be set up so that the 10,000 runs can be multi-threaded and take advantage of multi-processor cores. If portablity isn't a concern, maybe a native method would get you better speed than your statics do.

If for some reason you do not want multiple copies of an object, the singleton design pattern, has advantages over static objects, such as thread-safety (presuming your singleton is coded well), permitting lazy-initialization, guaranteeing the object has been properly initialized when it is used, sub-classing, advantages in testing and refactoring your code, not to mention, if at some point you change your mind about only wanting one instance of an object it is MUCH easier to remove the code to prevent duplicate instances than it is to refactor all your static variable code to use instance variables. I've had to do that before, its not fun, and you end up having to edit a lot more classes, which increases your risk of introducing new bugs...so much better to set things up "right" the first time, even if it seems like it has its disadvantages. For me, the re-work required should you decide down the road you need multiple copies of something is probably one of most compelling reasons to use statics as infrequently as possible. And thus I would also disagree with your statement that statics reduce inter-dependencies, I think you will end up with code that is more coupled if you have lots of statics that can be directly accessed, rather than an object that "knows how to do something" on itself.

静态变量本身并没有什么问题。只是Java语法有问题。每个Java类实际上定义了两个结构——一个封装静态变量的单例对象和一个实例。在同一个源代码块中定义这两种代码是非常糟糕的，会导致代码难以阅读。Scala做得很好。

一切(可以:)都有它的目的，如果你有一堆线程，需要共享/缓存数据和所有可访问的内存(所以你不分裂成上下文在一个JVM)静态是最好的选择->当然你可以强制只有一个实例，但为什么? 我发现这个帖子里的一些评论是邪恶的，不是静态的;)

我玩过很多静力学，我可以给你一个稍微不同的答案——或者可能是稍微不同的看待它的方式吗?

当我在一个类中使用静态(成员和方法)时，我最终开始注意到我的类实际上是两个分担责任的类——“静态”部分很像单例，而非静态部分(普通类)。据我所知，你可以通过为一个类选择所有静态类，为另一个类选择所有非静态类来完全分离这两个类。

当我在一个类中有一个静态集合，其中包含类的实例和一些静态方法来管理集合时，这种情况经常发生。一旦你思考一下，很明显你的类不是在做“一件事”，它是一个集合，做一些完全不同的事情。

现在，让我们稍微重构一下这个问题:如果你把你的类分成一个类，其中所有的东西都是静态的，而另一个类只是一个“普通类”，然后忘记“普通类”，那么你的问题就变成了纯静态类vs单例，这是在这里详细讨论的(可能还有其他十几个问题)。

静态变量没有好坏之分。它们表示描述整个类而不是特定实例的属性。如果需要为某个类的所有实例设置一个计数器，则静态变量将是保存该值的合适位置。

当您尝试使用静态变量来保存与实例相关的值时，就会出现问题。

我只是对回答中的一些观点进行了总结。如果你发现任何错误，请随时改正。

伸缩性:每个JVM只有一个静态变量实例。假设我们正在开发一个图书馆管理系统，我们决定将book的名称作为一个静态变量，因为每本书只有一个。但是如果系统增长了，我们使用了多个jvm，那么我们就没有办法知道我们在处理哪本书了?

线程安全:在多线程环境中使用实例变量和静态变量都需要控制。但对于实例变量，它不需要保护，除非它在线程之间显式地共享，但对于静态变量，它总是由进程中的所有线程共享。

测试:虽然可测试的设计并不等于好的设计，但我们很少会看到一个好的设计是不可测试的。由于静态变量代表全局状态，因此测试它们非常困难。

关于状态的推理:如果我创建一个类的新实例，那么我们可以推理这个实例的状态，但如果它有静态变量，那么它可以处于任何状态。为什么?因为静态变量可能已经被一些不同的实例修改过，因为静态变量是跨实例共享的。

序列化:序列化也不能很好地与它们一起工作。

创建和销毁:静态变量的创建和销毁是无法控制的。通常它们在程序加载和卸载时被创建和销毁。这意味着它们不利于内存管理，还会在启动时增加初始化时间。

但如果我们真的需要它们呢?

但有时我们可能真的需要它们。如果我们真的觉得需要在应用程序中共享许多静态变量，那么一种选择是使用单例设计模式，它将拥有所有这些变量。或者我们可以创建一些对象，它有这些静态变量，可以被传递。

同样，如果静态变量被标记为final，它就变成了一个常量，赋给它一次的值就不能改变了。这意味着它将把我们从由于其可变性而面临的所有问题中拯救出来。