在不影响arrayList顺序的情况下获取Java中arrayList中重复值的计数

Question

我正在尝试获取 String ArrayList 的重复值计数，我已完成任务但未完成。我能够得到 arrayList 的重复 elements 的 counts，但问题是 arrayList 的 order 当我得到 occurrences 共 elements

这是我的 code:

    Map<String, Integer> counts = new HashMap<String, Integer>();

    for (String str : t.courseName) {
        if (counts.containsKey(str)) {
            counts.put(str, counts.get(str) + 1);
        } else {
            counts.put(str, 1);
        }
    }

    for (Map.Entry<String, Integer> entry : counts.entrySet()) {
        System.out.println(entry.getKey() + " = " + entry.getValue());
    }

此代码可以很好地获取 occurrences，但请注意，此代码会破坏 order。我想要的是 order 也不应该被破坏。

Answer 1

使用 LinkedHashMap 而不是 HashMap 来保留插入顺序

A LinkedHashMap is a combination of hash table and linked list. It has a predictable iteration order (a la linked list), yet the retrieval speed is that of a HashMap. The order of the iteration is determined by the insertion order, so you will get the key/values back in the order that they were added to this Map.

在不影响arrayList顺序的情况下获取Java中arrayList中重复值的计数

Getting the count of duplicate values in arrayList in Java without affecting the order of arrayList

java

arraylist

hashmap

find-occurrences