枚举名称是否存在于 Java 中? [英] Are enum names interned in Java?

问题描述

枚举名称是否存在于 Java 中?

Are enum names interned in Java?

即是否保证 enum1.name() == enum2.name() 在同名的情况下?将 enum.name() 与保证被实习的字符串进行比较是否安全.

I.e. is it guaranteed that enum1.name() == enum2.name() in case of the same name? And is it safe to compare enum.name() to a String that is guaranteed to be interned.

推荐答案

虽然没有明确保证这一点，但最终结果必然是对于 enum 常量的比较总是成功的同名:

Although there is no explicit guarantee of this, the end result is bound to be such that the comparison always succeeds for enum constants with identical names:

enum A {enum1};
enum B {enum1};
System.out.println(A.enum1.name() == B.enum1.name()); // Prints "true"

这样做的原因是 Java 编译器以这样一种方式构造 Enum 的子类，它们最终会调用 Enum 唯一受保护的构造函数，并将其名称传递给它enum 值:

The reason for this is that Java compiler constructs subclasses of Enum in such a way that they end up calling Enum's sole protected constructor, passing it the name of enum value:

protected Enum(String name, int ordinal);

名称以字符串文字的形式嵌入到生成的代码中.根据 String 文档，

The name is embedded into the generated code in the form of a string literal. According to String documentation,

所有文字字符串和字符串值常量表达式都被插入.

All literal strings and string-valued constant expressions are interned.

这相当于当 enum 常量的名称相同时表达式成功的隐式保证.但是，我不会依赖这种行为，而是使用 equals(...) 代替，因为任何阅读我的代码的人都会挠头，认为我犯了一个错误.

This amounts to an implicit guarantee of your expression succeeding when names of enum constants are identical. However, I would not rely on this behavior, and use equals(...) instead, because anyone reading my code would be scratching his head, thinking that I made a mistake.

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