在 ArrayList() 中找到最常见的 String [英] Find the most common String in ArrayList()

问题描述

有没有办法在ArrayList中找到最常见的String?

ArrayListlist = new ArrayList<>();list.add("测试");list.add("测试");list.add("你好");list.add("测试");

应该从这个列表中找到单词test"["test","test","hello","test"]

解决方案

不要重新发明轮子，使用 Collections 类的 frequency 方法:

public static int frequency(Collectionc, Object o)

<块引用>

返回指定集合中元素的个数等于指定的对象.更正式地，返回元素数 e在集合中使得 (o == null ? e == null : o.equals(e)).

如果您需要计算所有元素的出现次数，请使用 Map 并巧妙地循环:)或者将您的列表放入一个集合中，并使用上面的 frequency 方法在集合的每个元素上循环.HTH

编辑/Java 8:如果您喜欢使用 lambda 表达式的功能更强大的 Java 8 单行解决方案，请尝试:

Map出现次数 =list.stream().collect(Collectors.groupingBy(w -> w, Collectors.counting()));

Is there a way to find the most common String in an ArrayList?

ArrayList<String> list = new ArrayList<>();
list.add("test");
list.add("test");
list.add("hello");
list.add("test");

Should find the word "test" from this list ["test","test","hello","test"]

解决方案

Don't reinvent the wheel and use the frequency method of the Collections class:

public static int frequency(Collection<?> c, Object o)

Returns the number of elements in the specified collection equal to the specified object. More formally, returns the number of elements e in the collection such that (o == null ? e == null : o.equals(e)).

If you need to count the occurrences for all elements, use a Map and loop cleverly :) Or put your list in a Set and loop on each element of the set with the frequency method above. HTH

EDIT / Java 8: If you fancy a more functional, Java 8 one-liner solution with lambdas, try:

Map<String, Long> occurrences = 
  list.stream().collect(Collectors.groupingBy(w -> w, Collectors.counting()));

这篇关于在 ArrayList() 中找到最常见的 String的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！