如何计算数组列表中单词的重复次数? [英] How to Count Repetition of Words in Array List?

问题描述

我有这些代码用于在 Array-List 中搜索出现，但我的问题是如何获得结果在整数类型的这个for循环的外面，因为我需要在外面，可能有另一种方法可以找到不使用 for 循环的情况你能帮帮我吗?谢谢...

I've these code for searching occurrence in Array-List but my problem is how I can get result out side of this for loop in integer type cause I need in out side , may be there is another way for finding occurrence with out using for loop can you help me ? thank you...

List<String> list = new ArrayList<String>();
list.add("aaa");
list.add("bbb");
list.add("aaa");

Set<String> unique = new HashSet<String>(list);
for (String key : unique) {
 int accurNO = Collections.frequency(list, key);
    System.out.println(key + ": " accurNO);
}

推荐答案

Set unique = new HashSet(list);

Set unique = new HashSet(list);

和

Collections.frequency(list, key);

Collections.frequency(list, key);

开销太大.

这是我要怎么做

List<String> list = new ArrayList<String>();
list.add("aaa");
list.add("bbb");
list.add("aaa");

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


for (String word : list) {
    Integer count = countMap.get(word);
    if(count == null) {
        count = 0;
    }
    countMap.put(word, (count.intValue()+1));
}

System.out.println(countMap.toString());

输出

{aaa=2, bbb=1}

EDIT 一一输出:遍历地图的条目集

EDIT output one by one: iterate over the set of entries of the map

for(Entry<String, Integer> entry : countMap.entrySet()) {
    System.out.println("frequency of '" + entry.getKey() + "' is "
          + entry.getValue());
}

输出

frequency of 'aaa' is 2
frequency of 'bbb' is 1

EDIT 2 无需循环

String word = null;
Integer frequency = null;

word = "aaa";
frequency = countMap.get(word);
System.out.println("frequency of '" + word + "' is " +
    (frequency == null ? 0 : frequency.intValue()));

word = "bbb";
frequency = countMap.get(word);
System.out.println("frequency of '" + word + "' is " + 
    (frequency == null ? 0 : frequency.intValue()));

word = "foo";
frequency = countMap.get(word);
System.out.println("frequency of '" + word + "' is " + 
    (frequency == null ? 0 : frequency.intValue()));

输出

frequency of 'aaa' is 2
frequency of 'bbb' is 1
frequency of 'foo' is 0

请注意，您将始终拥有一个集合，并且您需要以某种方式提取特定单词的计数.

Note that you will always have a collection and you need extract the count from it for a particular word one way or another.

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