跟踪文本文件中字符的频率

Question

So, for my current Data Structures project, I have to read a text file and eventually Huffman encode the characters, and then return the newly encoded file (I'm nowhere near any of this yet).

The first thing I have to do is scan through the file and determine the frequency of each character, and then create an ordered list of all the characters and their frequencies. However, I'm having trouble coming up with a good way of keeping a running total of frequencies and existing characters. I thought a Hashtable might be a good idea, where each key is a character, and the value it maps to is its frequency.

Is there a more efficient way to do this?

Thanks in advance!

Answer 1

Here is my code for find the character frequency using a text file.

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Locale;


public class Frequency2 {

    private static char[] myarry;
    private static int[] count = new int[26];
    private static double[] precntage=new double[26];
    private static double totCount=0;


    public static void main(String[] args) throws FileNotFoundException, IOException {

        String ss = new Frequency().readFile("E:/look.txt");//path of the text file
        //System.out.println(ss);
        ss = ss.toLowerCase(Locale.ENGLISH); // put all text to lowercase

        myarry = ss.toCharArray();  // text put a char array
        //count the characters
        for (int i = 0; i < myarry.length; i++) {
            if (myarry[i] == 'a') {
                count[0] = count[0] + 1;
            } else if (myarry[i] == 'b') {
                count[1] = count[1] + 1;
            } else if (myarry[i] == 'c') {
                count[2] = count[2] + 1;
            } else if (myarry[i] == 'd') {
                count[3] = count[3] + 1;
            } else if (myarry[i] == 'e') {
                count[4] = count[4] + 1;
            } else if (myarry[i] == 'f') {
                count[5] = count[5] + 1;
            } else if (myarry[i] == 'g') {
                count[6] = count[6] + 1;
            } else if (myarry[i] == 'h') {
                count[7] = count[7] + 1;
            } else if (myarry[i] == 'i') {
                count[8] = count[8] + 1;
            } else if (myarry[i] == 'j') {
                count[9] = count[9] + 1;
            } else if (myarry[i] == 'k') {
                count[10] = count[10] + 1;
            } else if (myarry[i] == 'l') {
                count[11] = count[11] + 1;
            } else if (myarry[i] == 'm') {
                count[12] = count[12] + 1;
            } else if (myarry[i] == 'n') {
                count[13] = count[13] + 1;
            } else if (myarry[i] == 'o') {
                count[14] = count[14] + 1;
            } else if (myarry[i] == 'p') {
                count[15] = count[15] + 1;
            } else if (myarry[i] == 'q') {
                count[16] = count[16] + 1;
            } else if (myarry[i] == 'r') {
                count[17] = count[17] + 1;
            } else if (myarry[i] == 's') {
                count[18] = count[18] + 1;
            } else if (myarry[i] == 't') {
                count[19] = count[19] + 1;
            } else if (myarry[i] == 'u') {
                count[20] = count[20] + 1;
            } else if (myarry[i] == 'v') {
                count[21] = count[21] + 1;
            } else if (myarry[i] == 'w') {
                count[22] = count[22] + 1;
            } else if (myarry[i] == 'x') {
                count[23] = count[23] + 1;
            } else if (myarry[i] == 'y') {
                count[24] = count[24] + 1;
            } else if (myarry[i] == 'z') {
                count[25] = count[25] + 1;
            }

        }



        for (int i = 0; i <count.length; i++) {
            totCount+=count[i];
        }

        System.out.println("tot "+ totCount);


       // calculate presentage
        for (int i = 0; i <count.length; i++) {
               precntage[i]=((count[i]/totCount)*100);
               precntage[i]=Math.round(precntage[i]);
        }




        char s1='A';
        System.out.println("Letter\tPrecentage\tFrequency");
        for (int i = 0; i < count.length; i++) {
            String gs=Character.toString(s1++);
            System.out.println(gs+"\t"+precntage[i]+"%"+"\t\t"+count[i]);
        }


    }

    String readFile(String fileName) throws IOException {
        BufferedReader buff = new BufferedReader(new FileReader(fileName));
        try {
            StringBuilder sb = new StringBuilder();
            String l = buff.readLine();

            while (l != null) {
                sb.append(l);
                sb.append("\n");
                l = buff.readLine();
            }
            return sb.toString();
        } finally {
            buff.close();
        }
    }

}

Hope this will help you.