从 Java 中的 ArrayList 获取唯一值
我有一个 ArrayList 有许多记录，一列包含气体名称，如 CO2 CH4 SO2 等.现在我只想检索不同的气体名称(唯一)而不从 数组列表.怎么办?
I have an ArrayList with a number of records and one column contains gas names as CO2 CH4 SO2, etc. Now I want to retrieve different gas names(unique) only without repeatation from the ArrayList. How can it be done?
推荐答案
你应该使用 设置.Set 是 Collection 不包含重复项.
You should use a Set. A Set is a Collection that contains no duplicates.
如果您有 列表 包含重复项，您可以像这样获取唯一条目:
If you have a List that contains duplicates, you can get the unique entries like this:
List<String> gasList = // create list with duplicates...
Set<String> uniqueGas = new HashSet<String>(gasList);
System.out.println("Unique gas count: " + uniqueGas.size());
注意:此 HashSet 构造函数通过调用元素的 equals() 方法来识别重复项.
NOTE: This HashSet constructor identifies duplicates by invoking the elements' equals() methods.
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