// Fig. 17.22: StreamOfLines.java
// Counting word occurrences in a text file.
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Map;
import java.util.TreeMap;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

public class StreamOfLines {
   public static void main(String[] args) throws IOException {
      // Regex that matches one or more consecutive whitespace characters
      Pattern pattern = Pattern.compile("\\s+"); 

      // count occurrences of each word in a Stream<String> sorted by word
      Map<String, Long> wordCounts =                             
         Files.lines(Paths.get("Chapter2Paragraph.txt"))         
              .flatMap(line -> pattern.splitAsStream(line))      
              .collect(Collectors.groupingBy(String::toLowerCase,
                 TreeMap::new, Collectors.counting()));          
      
      // display the words grouped by starting letter
      wordCounts.entrySet()                                         
         .stream()                                                  
         .collect(                                                  
            Collectors.groupingBy(entry -> entry.getKey().charAt(0),
               TreeMap::new, Collectors.toList()))                  
         .forEach((letter, wordList) -> {                           
            System.out.printf("%n%C%n", letter);                 
            wordList.stream().forEach(word -> System.out.printf( 
               "%13s: %d%n", word.getKey(), word.getValue()));   
         });                                                     
   }
} 


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