java 28 lines · 7 steps

Ranking the most frequent words in Java

A stream pipeline tokenizes text, counts each word, and returns the top entries in a stable, ordered map.

Explained by highlit
Intermediate streams regex grouping sorting word-count
1import java.util.Comparator;
2import java.util.LinkedHashMap;
3import java.util.Map;
4import java.util.regex.Pattern;
5import java.util.stream.Collectors;
6 
7public final class WordFrequencyAnalyzer {
8 
9 private static final Pattern WORD = Pattern.compile("[\\p{L}']+");
10 
11 public Map<String, Long> topWords(String text, int limit) {
12 return WORD.matcher(text.toLowerCase())
13 .results()
14 .map(match -> match.group())
15 .collect(Collectors.groupingBy(word -> word, Collectors.counting()))
16 .entrySet()
17 .stream()
18 .sorted(Map.Entry.<String, Long>comparingByValue()
19 .reversed()
20 .thenComparing(Map.Entry.comparingByKey()))
21 .limit(limit)
22 .collect(Collectors.toMap(
23 Map.Entry::getKey,
24 Map.Entry::getValue,
25 (a, b) -> a,
26 LinkedHashMap::new));
27 }
28}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Compiling a regex once as a static field avoids recompiling the pattern on every call.
  2. 2Collectors.groupingBy paired with Collectors.counting turns a stream of items into a frequency map in one pass.
  3. 3LinkedHashMap as the toMap supplier preserves the sorted iteration order that a plain HashMap would discard.

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