比较两个列表并从中删除重复项 [英] Comparing two lists and removing duplicates from one

问题描述

我有一个名为 FormObject 的对象，它包含两个 ArrayList - oldBooks 和 newBooks - 两者都包含 Book 对象.

I have an object called FormObject that contains two ArrayLists - oldBooks and newBooks - both of which contain Book objects.

oldBooks 允许包含重复的 Book 对象newBooks 不允许在其内部包含重复的 Book 对象，并且不能在 oldBooks 列表中包含任何重复的 Book 对象.

oldBooks is allowed to contain duplicate Book objects newBooks is not allowed to contain duplicate Book objects within itself and cannot include any duplicates of Book objects in the oldBooks list.

重复 Book 的定义很复杂，我无法覆盖 equals 方法，因为该定义在 Book 对象的所有用途中并不通用.

The definition of a duplicate Book is complex and I can't override the equals method as the definition is not universal across all uses of the Book object.

我计划在 FormObject 类上有一个名为 removeDuplicateNewBooks 的方法，它将执行上述功能.

I plan to have a method on the FormObject class called removeDuplicateNewBooks which will perform the above functionality.

您将如何实施?我的第一个想法是使用 HashSets 来消除重复项，但无法覆盖 Book 对象上的 equals 意味着它不起作用.

How would you go about implementing this? My first thought was to use HashSets to eliminate the duplicates but not being able to override equals on the Book object means it won't work.

推荐答案

您可以使用 TreeSet 与自定义 Comparator:

• 使用 Comparator 构建 TreeSet，实现您想要的自定义逻辑
• 使用 set.addAll(bookList)

• construct the TreeSet with a Comparator implementing the custom logic you want
• use set.addAll(bookList)

现在 Set 只包含独特的书籍.

Now the Set contains only unique books.

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