Java:避免在数组列表中插入重复项 [英] Java: Avoid inserting duplicate in arraylist

问题描述

我是 Java 新手.我有一个 ArrayList 并且我想避免在插入时重复.我的 ArrayList 是

I am novice to java. I have an ArrayList and I want to avoid duplicates on insertion. My ArrayList is

ArrayList<kar> karList = new ArrayList<kar>();

我要检查的字段是:

 kar.getinsertkar().

我已经读到我可以使用 HashSet 或 HashMap 但我不知道.

I have read that I can use HashSet or HashMap but I have no clue.

推荐答案

每当您想防止重复时，您都想使用 Set.

Whenever you want to prevent duplicates, you want to use a Set.

在这种情况下，HashSet 很适合您.

In this case, a HashSet would be just fine for you.

HashSet karSet = new HashSet();
karSet.add(foo);
karSet.add(bar);
karSet.add(foo);
System.out.println(karSet.size());
//Output is 2

为了完整起见，我还建议您使用类的通用(参数化)版本，假设是 Java 5 或更高版本.

For completeness, I would also suggest you use the generic (parameterized) version of the class, assuming Java 5 or higher.

HashSet<String> stringSet = new HashSet<String>();
HashSet<Integer> intSet = new HashSet<Integer>();
...etc...

这会给你一些类型安全以及将物品放入和取出你的集合.

This will give you some type safety as well for getting items in and out of your set.

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