java ArrayList中最常见的n字
我需要找到最频繁的单词n个单词,因此如果n=5,则在ArrayList中查找最频繁的5个单词java ArrayList中最常见的n字,java,sorting,arraylist,Java,Sorting,Arraylist,我需要找到最频繁的单词n个单词,因此如果n=5,则在ArrayList中查找最频繁的5个单词 private ArrayList<String> wordList = new ArrayList<String>(); public ArrayList<String> mostOften(int k) { ArrayList<String> lista = new ArrayList<String>(); Set<
private ArrayList<String> wordList = new ArrayList<String>();
public ArrayList<String> mostOften(int k)
{
ArrayList<String> lista = new ArrayList<String>();
Set<String> unique = new HashSet<String>(wordList);
for (String key : unique)
System.out.println(key + ": " + Collections.frequency(wordList, key));
return lista;
}
该函数需要返回按频率排序的最频繁单词的列表。如果两个单词的频率相同,我需要按字母顺序对它们进行排序。我已经发布了我尝试过的内容,但这只找到了频率,我不知道如何做其余的。有什么帮助吗?您可以编写一个比较器类,该类用列表初始化。然后可以使用列表和比较器调用Collections.sort。 代码可能如下所示:
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
public class FrequencyComparator implements Comparator<String>{
List<String> list;
@Override
public int compare(String o1, String o2) {
if (Collections.frequency(list, o1) > Collections.frequency(list, o2)){
return -1;
}else if (Collections.frequency(list, o1) < Collections.frequency(list, o2)){
return 1;
}else{
return o1.compareTo(o2);
}
}
public FrequencyComparator(List<String> list){
this.list = list;
}
public static void main(String[] args)
{
List<String> list = new ArrayList<String>();
list.add("Hello");
list.add("You");
list.add("Hello");
list.add("You");
list.add("Apple");
list.add("Apple");
list.add("Hello");
Set<String> unique = new HashSet<>(list);
List<String> uniqueList = new ArrayList<>(unique);
Collections.sort(uniqueList, new FrequencyComparator(list));
System.out.println(uniqueList);
//Take the most frequent 2 objects
System.out.println(uniqueList.subList(uniqueList.size() - 2, uniqueList.size());
}
}
下面是一个使用Java 8和streams的解决方案,包括计算词频、排序和限制为k个单词:
差不多好了。我需要将compareTo从现在的相反顺序反转。您可以在方法末尾使用Collections的reverse方法。您可以更改compareTo方法。只需将-1替换为1,将1替换为-1,我建议不要在比较中使用Collections.frequency。这样效率较低,但这仅在列表较长时才起作用Hello!我想问一下,您获取每个单词频率的方式与Java Collections.frequent获取单词的方式有什么区别,因为我试图在大量单词中找到最频繁的单词900000,因此,我使用Collection.frequent获取ArrayList中的每个单词的频率,我的计算机失败了,因为它太难处理。非常感谢。
class Pair {
String text;
int freq;
public Pair(String text, int freq) {
super();
this.text = text;
this.freq = freq;
}
}
public List<Pair> sortFreq(List<String> wordList) {
Set<String> unique = new HashSet<String>(wordList);
List<Pair> list = new ArrayList<Pair>(unique.size());
for (String key : unique) {
int freq = Collections.frequency(wordList, key);
Pair tempPair = new Pair(key, freq);
list.add(tempPair);
}
Collections.sort(list,new Comparator<Pair>() {
@Override
public int compare(Pair o1, Pair o2) {
if(o1.freq == o2.freq){
return o1.text.compareTo(o2.text);
}
return o2.freq - o1.freq;
}
});
return list;
}
public class WordFrequency {
public static void main(String[] args) {
List<String> list = new ArrayList<>();
list.add("Hello");
list.add("Hello");
list.add("aaaa");
list.add("aaaa");
list.add("World");
list.add("abc");
list.add("abc");
list.add("cba");
list.add("abc");
list.add("World");
list.add("abc");
System.out.println(mostOften(list));
}
public static List<Word> mostOften(List<String> words){
Map<String, Word> wordMap = new HashMap<>();
for (String word : words) {
Word currentWord = wordMap.get(word);
if(currentWord == null)
wordMap.put(word, new Word(word, 1));
else
currentWord.frequency++;
}
List<Word> wordList = new ArrayList<>(wordMap.values());
wordList.sort(new Comparator<Word>() {
@Override
public int compare(Word o1, Word o2) {
if(o1.frequency == o2.frequency)
return o1.word.compareToIgnoreCase(o2.word);
/* sort words with high frequency first */
return Integer.compare(o2.frequency, o1.frequency);
}
});
return wordList;
}
}
public class Word{
String word;
int frequency;
public Word(String word, int total) {
this.word = word;
this.frequency = total;
}
public String toString(){
return "[" + word + ", " + frequency + "]";
}
}
List<String> wordList = new ArrayList<String>();
int k = 5;
List<String> mostFrequentWords = wordList.stream().collect(Collectors.collectingAndThen(
Collectors.groupingBy(Function.identity(), Collectors.counting()),
map -> map.entrySet().stream()
.sorted(Comparator.<Entry<String, Long>> comparingLong(Entry::getValue).reversed()
.thenComparing(Entry::getKey))
.map(Entry::getKey)
.limit(k)
.collect(Collectors.toList())));