求一篇文章各个英文字母出现的频率

求一篇英文文章中各个字母出现的频率,不区分大小写.
思路:

(1)首先定义一个数组freArray= new int[26],存放每个单词的出现频率.
(2)读取该篇文章到内存中，并形成一个字符数组.
(3)遍历该字符数组
----首先判断被遍历到字符c的ascii值是否大于'A'而且小于'Z'，如果是，则freArray[c-'A']++
----然后判断被遍历到字符c的ascii值是否大于'a'而且小于'z',如果是,则freArray[c-'a']++

(4)然后输出freeArray中各个字母的统计值.

实现代码(Java):

package com.test.test;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class ComputeCharFrequency {

    /**
     * Compute the frequencies of letter occurrence
     * 
     * @param args
     */
    public static void main(String[] args) {
        int[] freArray = new int[26];
        char[] charArray = loadCharArrayFromFileName("c:/article.txt");

        computeFrequency(freArray, charArray);
        for (int i = 0; i < freArray.length; i++) {
            System.out.println(((char) ('a' + i)) + ":" + freArray[i]);

        }
    }

    public static void computeFrequency(int[] freArray, char[] charArray) {
        for (int i = 0; i < charArray.length; i++) {
            if (charArray[i] >= 'A' && charArray[i] <= 'Z') {
                freArray[charArray[i] - 'A']++;

            }
            if (charArray[i] >= 'a' && charArray[i] <= 'z') {
                freArray[charArray[i] - 'a']++;

            }

        }

    }
    /**
     * read a text file's content to a Char Array
     * @param name
     * @return Char Array
     */
    public static char[] loadCharArrayFromFileName(String name) {
        char[] charArray = new char[50000];
        File file = new File(name);
        FileReader fr = null;
        try {
            fr = new FileReader(file);
            fr.read(charArray);
            return charArray;
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            try {
                fr.close();
            } catch (IOException e) {

                e.printStackTrace();
            }

        }
        return null;
    }

}