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

Space play ←→ step click any line
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.

Related explainers

java 
public final class HttpHeaders {
 
    private final NavigableMap<String, List<String>> values =
            new TreeMap<>(String.CASE_INSENSITIVE_ORDER);

A case-insensitive HTTP headers map in Java

case-insensitivity multimap immutability
Intermediate 7 steps
rust 
use axum::{
    extract::State,
    response::sse::{Event, KeepAlive, Sse},
};

Broadcasting live prices over SSE in Axum

server-sent-events broadcast-channel streams
Advanced 9 steps
java 
public record ServerConfig(
        String host,
        int port,
        Duration timeout,

Loading typed config into a Java record

records factory-methods parsing
Intermediate 7 steps
java 
public final class IbanValidator {
 
    private static final Map<String, Integer> COUNTRY_LENGTHS = Map.ofEntries(
        Map.entry("DE", 22), Map.entry("FR", 27), Map.entry("GB", 22),

Validating IBANs with the mod-97 checksum

validation checksum modular-arithmetic
Intermediate 8 steps
python 
import re
from collections import Counter
from pathlib import Path
 

Ranking the top words in a PDF

text-processing regex counting
Intermediate 6 steps
java 
@Configuration
@EnableWebSecurity
public class OAuth2SecurityConfig {
 

How OIDC login works in Spring Security

oauth2 openid-connect authorization
Intermediate 8 steps

Share this explainer

Here's the card — post it anywhere.

Ranking the most frequent words in Java — share card
Made with highlit — turn any snippet into a walkthrough like this in about a minute.
Explain your code