java - 为什么 boolean 对象在 Java 中有一个公共(public)构造函数？

Question

Java 中构造函数 new Boolean(boolean value) 的文档说明:

Note: It is rarely appropriate to use this constructor. Unless a new instance is required, the static factory valueOf(boolean) is generally a better choice. It is likely to yield significantly better space and time performance.

如果是这样，为什么这个构造函数是公开的而不被弃用？是否有充分的理由使用此构造函数而不是 Boolean.valueOf()？

Answer 1

valueOf() 仅在 Java 1.4 中添加，因此看起来构造函数的存在是为了向后兼容。

This ticket解释了不弃用构造函数的原因:

Due to the disruption deprecating an API can have, currently an API has to be "actively hazardous" to be deprecated, like Thread.stop. While the use this constructor is certainly ill-advised, it doesn't rise (or sink) to the standard of hazardousness to be deprecated in the JDK. In the future we may add a "denigration" facility to mark API elements that aren't quite so bad that they should be deprecated, but shouldn't be used in most cases. This constructor would be a good candidate for denigration.

我想不出一个现实的场景，使用 Boolean 构造函数会是做一些有用的事情的最佳方式。