WordCount.java Source code

Introduction

Here is the source code for WordCount.java

Source

import java.io.FileInputStream;
import java.nio.CharBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.util.Map;
import java.util.TreeMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class WordCount {
    public static void main(String args[]) throws Exception {
        String filename = "WordCount.java";

        // Map File from filename to byte buffer
        FileInputStream input = new FileInputStream(filename);
        FileChannel channel = input.getChannel();
        int fileLength = (int) channel.size();
        MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, fileLength);

        // Convert to character buffer
        Charset charset = Charset.forName("ISO-8859-1");
        CharsetDecoder decoder = charset.newDecoder();
        CharBuffer charBuffer = decoder.decode(buffer);

        // Create line pattern
        Pattern linePattern = Pattern.compile(".*$", Pattern.MULTILINE);

        // Create word pattern
        Pattern wordBreakPattern = Pattern.compile("[\\p{Punct}\\s}]");

        // Match line pattern to buffer
        Matcher lineMatcher = linePattern.matcher(charBuffer);

        Map map = new TreeMap();
        Integer ONE = new Integer(1);

        // For each line
        while (lineMatcher.find()) {
            // Get line
            CharSequence line = lineMatcher.group();

            // Get array of words on line
            String words[] = wordBreakPattern.split(line);

            // For each word
            for (int i = 0, n = words.length; i < n; i++) {
                if (words[i].length() > 0) {
                    Integer frequency = (Integer) map.get(words[i]);
                    if (frequency == null) {
                        frequency = ONE;
                    } else {
                        int value = frequency.intValue();
                        frequency = new Integer(value + 1);
                    }
                    map.put(words[i], frequency);
                }
            }
        }
        System.out.println(map);
    }
}