import java.util.ArrayList; import java.util.Collections; import java.util.TreeMap; import java.util.Comparator; /** * This program will read words from an input file, and count the * number of occurrences of each word. The word data is written to * an output file twice, once with the words in alphabetical order * and once with the words ordered by number of occurrences. The * user specifies the input file and the output file. * * The program demonstrates several parts of Java's framework for * generic programming: TreeMap, List sorting, Comparators, etc. */ public class WordCount { /** * Represents the data we need about a word: the word and * the number of times it has been encountered. */ private static class WordData { String word; int count; WordData(String w) { // Constructor for creating a WordData object when // we encounter a new word. word = w; count = 1; // The initial value of count is 1. } } // end class WordData /** * A comparator for comparing objects of type WordData according to * their counts. This is used for sorting the list of words by frequency. */ private static class CountCompare implements Comparator { public int compare(WordData data1, WordData data2) { return data2.count - data1.count; // The return value is positive if data2.count > data1.count. // I.E., data1 comes after data2 in the ordering if there // were more occurrences of data2.word than of data1.word. // The words are sorted according to decreasing counts. } } // end class CountCompare public static void main(String[] args) { System.out.println("\n\n This program will ask you to select an input file"); System.out.println("It make a list of all the words that occur in the file"); System.out.println("along with the number of time that each word occurs."); System.out.println("This list will be output twice, first in alphabetical,"); System.out.println("then in order of frequency of occurrence with the most"); System.out.println("common word at the top and the least common at the end."); System.out.println(" After reading the input file, the program asks you to"); System.out.println("select an output file. If you select a file, the list of"); System.out.println("words will be written to that file; if you cancel, the list"); System.out.println("be written to standard output. All words are converted to"); System.out.println("lower case.\n\n"); System.out.print("Press return to begin."); TextIO.getln(); // Wait for user to press return. try { if (TextIO.readUserSelectedFile() == false) { System.out.println("No input file selected. Exiting."); System.exit(1); } // Create a TreeMap to hold the data. Read the file and record // data in the map about the words that are found in the file. TreeMap words = new TreeMap(); String word = readNextWord(); while (word != null) { word = word.toLowerCase(); // convert word to lower case WordData data = words.get(word); if (data == null) words.put( word, new WordData(word) ); else data.count++; word = readNextWord(); } System.out.println("Number of different words found in file: " + words.size()); System.out.println(); if (words.size() == 0) { System.out.println("No words found in file."); System.out.println("Exiting without saving data."); System.exit(0); } // Copy the word data into an array list, and sort the list // into order of decreasing frequency. ArrayList wordsByFrequency = new ArrayList( words.values() ); Collections.sort( wordsByFrequency, new CountCompare() ); // Output the data from the map and from the list. TextIO.writeUserSelectedFile(); // If user cancels, output automatically // goes to standard output. TextIO.putln(words.size() + " words found in file:\n"); TextIO.putln("List of words in alphabetical order" + " (with counts in parentheses):\n"); for ( WordData data : words.values() ) TextIO.putln(" " + data.word + " (" + data.count + ")"); TextIO.putln("\n\nList of words by frequency of occurence:\n"); for ( WordData data : wordsByFrequency ) TextIO.putln(" " + data.word + " (" + data.count + ")"); System.out.println("\n\nDone.\n\n"); } catch (Exception e) { System.out.println("Sorry, an error has occurred."); System.out.println("Error Message: " + e.getMessage()); e.printStackTrace(); } System.exit(0); // Might be necessary, because of use of file dialogs. } /** * Read the next word from TextIO, if there is one. First, skip past * any non-letters in the input. If an end-of-file is encountered before * a word is found, return null. Otherwise, read and return the word. * A word is defined as a sequence of letters. Also, a word can include * an apostrophe if the apostrophe is surrounded by letters on each side. * @return the next word from TextIO, or null if an end-of-file is encountered */ private static String readNextWord() { char ch = TextIO.peek(); // Look at next character in input. while (ch != TextIO.EOF && ! Character.isLetter(ch)) { TextIO.getAnyChar(); // Read the character. ch = TextIO.peek(); // Look at the next character. } if (ch == TextIO.EOF) // Encountered end-of-file return null; // At this point, we know that the next character, so read a word. String word = ""; // This will be the word that is read. while (true) { word += TextIO.getAnyChar(); // Append the letter onto word. ch = TextIO.peek(); // Look at next character. if ( ch == '\'' ) { // The next character is an apostrophe. Read it, and // if the following character is a letter, add both the // apostrophe and the letter onto the word and continue // reading the word. If the character after the apostrophe // is not a letter, the word is done, so break out of the loop. TextIO.getAnyChar(); // Read the apostrophe. ch = TextIO.peek(); // Look at char that follows apostrophe. if (Character.isLetter(ch)) { word += "\'" + TextIO.getAnyChar(); ch = TextIO.peek(); // Look at next char. } else break; } if ( ! Character.isLetter(ch) ) { // If the next character is not a letter, the word is // finished, so bread out of the loop. break; } // If we haven't broken out of the loop, next char is a letter. } return word; // Return the word that has been read. } } // end class WordCount