英文字母频率统计

　　读取文件，统计各个字母出现的频率。

源程序：

  1 /**
  2  * Count the frequence of each character by reading a file.
  3  *
  4  * @author LuoPeng
  5  * @time 2015.3.5
  6  *
  7  */
  8 public class CharacterFrequence {
  9
 10     /**
 11      * Count the frequence of each character
 12      * @param filePath the path of the file to be read
 13      * @return the frequence of each character
 14      */
 15     public double[] countFrequence ( String filePath ) {
 16
 17         double [] frequence = null;
 18         int [] counts = null;
 19         long totalCharacter = 0L;
 20         BufferedReader br = null;
 21
 22         try {
 23             // Get the reader
 24             br = new BufferedReader(new InputStreamReader(new FileInputStream(filePath)));
 25             // Read message from the file if the reader is not null
 26             if ( br != null ) {
 27                 // Make and initialize the array
 28                 frequence = new double[26];
 29                 counts = new int[26];
 30
 31                 // Store the message of each line
 32                 String line = br.readLine();
 33                 // Store the length of line
 34                 int tempCount = 0;
 35                 // The loop variable
 36                 int i = 0;
 37                 while ( line != null ) {
 38                     line = line.trim().toLowerCase();
 39                     tempCount = line.length();
 40                     for ( i = 0; i < tempCount; i++ ) {
 41                         switch (line.charAt(i)) {
 42                         case ‘a‘:
 43                             counts[0]++;
 44                             break;
 45                         case ‘b‘:
 46                             counts[1]++;
 47                             break;
 48                         case ‘c‘:
 49                             counts[2]++;
 50                             break;
 51                         case ‘d‘:
 52                             counts[3]++;
 53                             break;
 54                         case ‘e‘:
 55                             counts[4]++;
 56                             break;
 57                         case ‘f‘:
 58                             counts[5]++;
 59                             break;
 60                         case ‘g‘:
 61                             counts[6]++;
 62                             break;
 63                         case ‘h‘:
 64                             counts[7]++;
 65                             break;
 66                         case ‘i‘:
 67                             counts[8]++;
 68                             break;
 69                         case ‘j‘:
 70                             counts[9]++;
 71                             break;
 72                         case ‘k‘:
 73                             counts[10]++;
 74                             break;
 75                         case ‘l‘:
 76                             counts[11]++;
 77                             break;
 78                         case ‘m‘:
 79                             counts[12]++;
 80                             break;
 81                         case ‘n‘:
 82                             counts[13]++;
 83                             break;
 84                         case ‘o‘:
 85                             counts[14]++;
 86                             break;
 87                         case ‘p‘:
 88                             counts[15]++;
 89                             break;
 90                         case ‘q‘:
 91                             counts[16]++;
 92                             break;
 93                         case ‘r‘:
 94                             counts[17]++;
 95                             break;
 96                         case ‘s‘:
 97                             counts[18]++;
 98                             break;
 99                         case ‘t‘:
100                             counts[19]++;
101                             break;
102                         case ‘u‘:
103                             counts[20]++;
104                             break;
105                         case ‘v‘:
106                             counts[21]++;
107                             break;
108                         case ‘w‘:
109                             counts[22]++;
110                             break;
111                         case ‘x‘:
112                             counts[23]++;
113                             break;
114                         case ‘y‘:
115                             counts[24]++;
116                             break;
117                         case ‘z‘:
118                             counts[25]++;
119                             break;
120                             default:
121                                 ;
122                         }
123                     }
124                     line = br.readLine();
125                 }
126
127                 // calculate the number of characters
128                 for ( i = 0; i < counts.length; i++ ) {
129                     totalCharacter += counts[i];
130                 }
131                 // calculate the frequence
132                 for ( i = 0; i < frequence.length; i++ ) {
133                     frequence[i] = 1.0*counts[i]/totalCharacter;
134                 }
135             }
136         } catch (FileNotFoundException e) {
137             e.printStackTrace();
138             System.out.println("Could not find the file...");
139         } catch (IOException e) {
140             e.printStackTrace();
141             System.out.println("Read message error...");
142         } finally {
143             // Close the IO
144             try {
145                 br.close();
146             } catch (IOException e) {
147                 e.printStackTrace();
148                 System.out.println("Close IO exception...");
149             }
150         }
151
152         return frequence;
153
154     }
155 }

统计结果：

　　上述两张图片的结果分别对应两篇文章《The Sorrows of Young Werther》和《Anna Karenina》，纵坐标表示出现的频率，横坐标对应各个字母（1对应a，2对应b，……，26对应z）。