Java HashMap example

 
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
 
public class HashMapEx {
 
    public static void main(String[] args) {
        // Creating new HashMap objects
        // keys are String, values are Integer
        HashMap<String, Integer> wordcount = new HashMap<String, Integer>();
 
        try {
            // Opening file
            // change "/Users/anyexample/input.txt" to path to your test file 
            BufferedReader in = new BufferedReader(new FileReader(
                    "/Users/andrian/input.txt"));
            // string buffer for file reading  
            String str;
 
            // reading line by line from file   
            while ((str = in.readLine()) != null) {
                str = str.toLowerCase(); // convert to lower case
 
                // starting index, we'll use this to copy words from string
                int idx1 = -1;
                // process each characters 
                for (int i = 0; i < str.length(); i++) {
                    // trigger condition if current character is not letter
                    // or it is the end of line 
                    if ((!Character.isLetter(str.charAt(i))) || (i + 1 == str.length())) {
                        // do nothing if previous character was also non-letter
                        if (i - idx1 > 1) {
                            // copy word from input string buffer to new variable 
                            // from previous non-letter symbol 
                            // to current symbol which is also non-letter
 
                            // if this is a letter(than it is last character in the line 
                            // and we should copy it to word)  
                            if (Character.isLetter(str.charAt(i)))
                                i++;
 
                            // copying... 
                            String word = str.substring(idx1 + 1, i);
 
                            // Check if word is in HashMap
                            if (wordcount.containsKey(word)) {
                                // get number of occurrences for this word
                                // increment it 
                                // and put back again 
                                wordcount.put(word, wordcount.get(word) + 1);
                            } else {
                                // this is first time we see this word, set value '1'
                                wordcount.put(word, 1);
                            }
                        }
 
                        // remember current position as last non-letter symbol                        
                        idx1 = i;
                    }
                }
            }
            // Close buffered reader
            in.close();
        } catch (Exception e) {
            // If something unexpected happened 
            // print exception information and quit 
            e.printStackTrace();
            System.exit(1);
        }
 
        // This code sorts outputs HashMap sorting it by values
 
        // First we're getting values array 
        ArrayList<Integer> values = new ArrayList<Integer>();
        values.addAll(wordcount.values());
        // and sorting it (in reverse order)
        Collections.sort(values, Collections.reverseOrder());
 
        int last_i = -1;
        // Now, for each value 
        for (Integer i : values) {
            if (last_i == i) // without dublicates 
                continue;
            last_i = i;
            // we print all hash keys 
            for (String s : wordcount.keySet()) {
                if (wordcount.get(s) == i) // which have this value 
                    System.out.println(s + ":" + i);
            }
            // pretty inefficient, but works 
        }
    }
}