Google Collections独特谓词 [英] Google Collections Distinct Predicate

问题描述

一个人如何实现与Google Collections Collections2.filter方法一起使用的谓词?

How would one implement a distinct predicate for use with the Google Collections Collections2.filter method?

推荐答案

如果我对您的理解正确，那么我不确定在这里谓词是否是正确的解决方案:

If I understand you correctly, I'm not sure that Predicate is the right solution here:

创建这样的谓词将需要维护某种状态(即:维护已经看到的一组事物).在Javadoc中明确建议不要这样做.

Creating a predicate like that would require maintaining some sort of state (ie: maintaining a Set of things it has seen already). This is explicitly advised against in the javadoc.

获取集合中不同项目的通常方法是将它们全部添加到集合中.即:

The usual way to get the distinct items in a collection would be to just add them all to a set. ie:

Set<T> uniqueItems = Sets.newHashSet(collectionWithPotentialDuplicates);

如果<T>上的equals()和hashCode()方法未按所需方式定义唯一性，则应编写一个对Collection<T>和Function<T, Object>进行操作的实用程序方法，该方法将返回项目类型T的类型，在使用Function

If the equals() and hashCode() methods on <T> don't define uniqueness the way you want, then you should write a utility method that operates on a Collection<T> and a Function<T, Object> which returns the items of type T which are unique after being converted using the Function

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