为什么布尔包装器类实现Serializable接口和Comparable接口?有什么用? [英] Why Boolean wrapper class implements Serializable interface and Comparable interface ? What is the use of it?
问题描述
为什么布尔和字符包装类正在实现Serializable接口和Comparable接口?它有什么用?
Why Boolean and Character wrapper classes are implementing Serializable interface and Comparable interface ? What is the use of it?
推荐答案
The Comparable interface was added to the Boolean class in Java 5, to address bug JDK-4329937, and at least one other. One of the issues cited was sorting boolean columns in a JTable.
最初，不少于 Joshua Bloch :
当前的设计与语言本身是一致的:尝试对两个布尔值进行比较会导致编译时错误:
The current design is consistent with the language itself: it is a compile-time error to attempt to compare two booleans for order:
if (true < false) // ERROR: WON'T COMPILE
foo();
包装器类(布尔)仅反映包装的基元的行为....
The wrapper class (Boolean) merely mirrors the behavior of the wrapped primitive. ...
我们愿意牺牲这种设计纯度".在实用主义的祭坛上，但我不相信确实需要比较布尔值.要对布尔值列表进行排序非常罕见.更常见的是要基于此字段对包含布尔字段的对象列表进行排序，但是这样做需要使用Comparator.无论如何，如果您正在编写比较器，即使布尔本身不实现Comparable，也可以基于Boolean字段进行排序很简单.
We would be willing to sacrifice this "design purity" on the altar of pragmatism, but I'm not convinced that there is a real need for comparing Booleans. It is extraordinarily rare to want to sort a list of Booleans. More common is to want to sort a list of objects containing a Boolean field based on this field, but doing this requires the use of a Comparator. If you're writing a Comparator anyway, it's straightforward to sort based on the Boolean field even though Boolean does not, itself, implement Comparable.
但是几年后，该实用程序得到了认可:
But several years later, the utility was acknowledged:
多年来，很明显，如果我们提供此功能，它将使人们的生活更加轻松.
Over the years it has become apparent that it would make life easier for people if we provided this functionality.
自从实施了此增强功能以来，它就变得更加有用.例如，在 Java 8 中，
Since this enhancement was implemented, it's become even more useful. For example, in Java 8, the Comparator class introduced new methods comparing() and thenComparing, that can build a comparator based on fields. And it can be reasonable and useful to include a boolean field as part of sort criteria.
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