A Java class to do some very basic analysis of a list of data scientist job postings.

JobAnalysis.java

package com.swgoof.datascience.job;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;

/**
 * This file is used to count the number of times a word appears in a file.
 * The class reads a file of data scientist job descriptions, 
 * each separated by '--'
 * It also keeps track of whether a word occurs in each job description.
 */
public class JobAnalysis {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws FileNotFoundException, IOException {
        BufferedReader in = new BufferedReader(new FileReader("datasciencejobs.txt"));
        int numOfJobs = 16;
        int jobCounter = 0;
        Map<String, WordObj> words = new HashMap<String, WordObj>(150);
        String line = in.readLine();
        do {
            if (line.startsWith("--")) {
                jobCounter++;
            }
            line = line.toLowerCase();
            // replace all dots with nothing
            line = line.replaceAll("\\.", "");
            // replace all special chars with space
            line = line.replaceAll("[^A-Za-z0-9]", " ");
            //System.out.println(line);
            StringTokenizer sp = new StringTokenizer(line);
            while (sp.hasMoreTokens()) {
                String word = sp.nextToken();
                //System.out.println("word:: " + word);
                WordObj tmp = words.get(word);
                if (tmp != null) {
                    //System.out.println("found: " + word);
                    // inc counter
                    tmp.increment(jobCounter);
                    words.put(word, tmp);
                } else {
                    WordObj wordObj = new WordObj(numOfJobs);
                    wordObj.flagJob(jobCounter);
                    words.put(word, wordObj);
                }
            }
            line = in.readLine();
        } while (line != null);
        in.close();

        //Map<String, Integer> sortedWords = sortForMap(words);
        List<Map.Entry<String, WordObj>> sortedWords = sortForListForWordObj(words);
        for (Map.Entry<String, WordObj> entry : sortedWords) {
            System.out.printf("'%s' %s \n", entry.getKey(), entry.getValue());
        }
        System.out.println("total words: " + sortedWords.size());
    }
    
    /**
     * This method will return a sorted List of WordObjs.
     * 
     * @param unsortMap
     * @return 
     */
    private static List<Map.Entry<String, WordObj>> sortForListForWordObj(Map<String, WordObj> unsortMap) {

        List<Map.Entry<String, WordObj>> sortedList = new ArrayList(unsortMap.entrySet());

        //sort list based on comparator
        Collections.sort(sortedList, new Comparator() {

            @Override
            public int compare(Object o1, Object o2) {
                return ((Comparable) ((WordObj)((Map.Entry) (o1)).getValue()).getNum()).compareTo(((WordObj)((Map.Entry) (o2)).getValue()).getNum());
            }
        });

        return sortedList;
    }
}

/**
 * A class to keep track of how many times a word occurs and which
 * job posts it appears in.
 */
class WordObj {

    /** number of times the word occurs */
    private Integer num;
    private Boolean[] inJobs;  // a true means the word is in that job

    public WordObj(int numOfJobs) {
        this.num = 1;
        this.inJobs = new Boolean[numOfJobs];
    }

    public void increment(int jobNum) {
        this.flagJob(jobNum);
        num++;
    }
    
    public void flagJob(int jobNum) { 
        if (jobNum >= 0 && jobNum < inJobs.length) {
            this.inJobs[jobNum] = Boolean.TRUE;
        }
    }

    @Override
    public String toString() {
        int counter = 0;
        for (Boolean b : inJobs) {
            if (b != null && b) {
                counter++;
            }
        }
        return String.format(" occured %d times and in %d job descriptions" , getNum(), counter);
    }

    /**
     * @return the num
     */
    public Integer getNum() {
        return num;
    }
}