有趣的统计英文字母频率的例子

统计的是英文版"悲惨世界"，代码如下，使用ascii值做数组下标直接赋值：

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.text.DecimalFormat;

public class EnglishAlphaBetaStatics {
	public static final String EN_FOLDER = "C:/resources/Books/English/Les Miserables.txt";
	private static final int ASCII_START = 33; // ASCII from 33; ignore the
												// space
	private static final int ASCII_LENGTH = 94;

	private int[] result = new int[ASCII_LENGTH];
	private int total = 0;

	/**
	 * Handle one English fiction
	 * 
	 * @param file
	 * @throws IOException
	 */
	public void handleOneFile(File file) throws IOException {
		if (file == null)
			throw new NullPointerException();

		BufferedReader in = new BufferedReader(new FileReader(file));
		String line;

		while ((line = in.readLine()) != null) {
			for (int i = 0; i < line.length(); i++) {
				char c = line.charAt(i);

				if (c >= ASCII_START && c < ASCII_START + ASCII_LENGTH) {
					result[c - ASCII_START] += 1;
					total++;
				} else {

				}
			}
		}
		in.close();
	}

	/**
	 * Print the statics result
	 */
	public void printResult() {
		// For sorting
		int[] abc = new int[ASCII_LENGTH];
		for (int i = 0; i < abc.length; i++) {
			abc[i] = ASCII_START + i;
		}

		// Sorting
		for (int i = 0; i < result.length; i++) {
			for (int j = 0; j < result.length - 1 - i; j++) {
				if (result[j] < result[j + 1]) {
					int tmp = result[j];
					result[j] = result[j + 1];
					result[j + 1] = tmp;
					// swap the characters
					tmp = abc[j];
					abc[j] = abc[j + 1];
					abc[j + 1] = tmp;
				}
			}
		}

		// Format
		DecimalFormat df = new DecimalFormat("#.######");

		System.out.println("Total characters: " + total);
		System.out.println("Char\tNumber\t%");
		System.out.println("-----------------------------------");
		for (int i = 0; i < result.length; i++) {
			char c = (char) abc[i];
			double rate = result[i] * 100.0 / total;
			System.out.println(c + "\t" + result[i] + "\t" + df.format(rate)
					+ "%");
		}
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) throws IOException {
		EnglishAlphaBetaStatics eab = new EnglishAlphaBetaStatics();
		eab.handleOneFile(new File(EN_FOLDER));
		eab.printResult();
	}
}

我以为会多慢呢，没想到瞬间完成，统计结果如下：

Total characters: 2800496
Char	Number	%
-----------------------------------
e	345891	12.351062%
t	235280	8.401369%
a	211330	7.546163%
o	190799	6.813043%
h	180302	6.438217%
n	176170	6.290671%
i	174552	6.232896%
s	166855	5.958052%
r	152896	5.459604%
d	113123	4.039392%
l	102527	3.66103%
u	70975	2.534372%
c	66061	2.358904%
m	59036	2.108055%
w	56513	2.017964%
f	56476	2.016643%
,	51714	1.846601%
g	48633	1.736585%
p	41978	1.498949%
y	39999	1.428283%
b	36215	1.293164%
.	32322	1.154153%
v	25400	0.906982%
k	14724	0.525764%
"	14616	0.521908%
T	12625	0.450813%
-	10222	0.365007%
I	9530	0.340297%
A	6890	0.246028%
H	6553	0.233994%
M	6435	0.229781%
;	6204	0.221532%
E	4313	0.154008%
S	4292	0.153259%
C	4262	0.152187%
x	3882	0.138618%
'	3852	0.137547%
!	3690	0.131762%
O	3593	0.128299%
j	3495	0.124799%
B	3476	0.124121%
W	3316	0.118408%
?	3094	0.11048%
R	3057	0.109159%
P	3047	0.108802%
F	2811	0.100375%
N	2751	0.098233%
:	2553	0.091162%
J	2536	0.090555%
q	2535	0.09052%
G	2401	0.085735%
L	2296	0.081985%
V	2021	0.072166%
z	1960	0.069988%
D	1735	0.061953%
Y	1147	0.040957%
U	768	0.027424%
1	687	0.024531%
K	600	0.021425%
8	422	0.015069%
*	303	0.01082%
X	262	0.009355%
2	243	0.008677%
3	237	0.008463%
`	227	0.008106%
5	203	0.007249%
[	197	0.007034%
]	197	0.007034%
0	195	0.006963%
4	155	0.005535%
7	142	0.005071%
6	133	0.004749%
Q	121	0.004321%
9	113	0.004035%
(	95	0.003392%
)	95	0.003392%
Z	58	0.002071%
_	40	0.001428%
|	36	0.001285%
{	2	0.000071%
}	2	0.000071%
+	1	0.000036%
/	1	0.000036%
#	0	0%
$	0	0%
%	0	0%
&	0	0%
<	0	0%
=	0	0%
>	0	0%
@	0	0%
\	0	0%
^	0	0%
~	0	0%