java类的最终字段是否应该是静态的？ [英] Should a java class' final fields always be static?

问题描述

我在网上找不到任何有关此内容的参考资料。但只是想知道一个类中的最终字段是否应始终为 static ，还是只是一个约定。基于我对它们的用途的理解，我觉得这比用语言强加的东西更合乎逻辑。

I could not find any references online about this. But just wanted to know if final fields in a class should always be static or is it just a convention. Based on my understanding of their uses, I feel that it is more of a logical thing to do than something that is imposed by the language.

推荐答案

当然不是。如果它们属于类，则它们必须是静态的，如果它们属于类的实例，则它们不是静态的：

Of course not. They must be static if they belong to the class, and not be static if they belong to the instance of the class:

public class ImmutablePerson {
    private static final int MAX_LAST_NAME_LENGTH = 255; // belongs to the type
    private final String firstName; // belongs to the instance
    private final String lastName; // belongs to the instance

    public ImmutablePerson(String firstName, String lastName) {
        if (lastName.length() > MAX_LAST_NAME_LENGTH) {
            throw new IllegalArgumentException("last name too large");
        }
        this.firstName = firstName;
        this.lastName = lastName;
    }

    // getters omitted for brevity
}

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