[求助]帮看看这个程序...

[ShingU]

这个程序是用来统计输入的字符串中每个字母出现的次数,编译能通过,但是运行的时候就出错了,是下标越界,但是不是很清楚哪里的问题...

import java.io.*;

public class CalculateFrequency
{
public static void main(String[] args) throws Exception
{
int[] frequencyTable = new int[26];

for (int i=0;i<26;i++)
{
frequencyTable[i] = 0;
}

DataInputStream in = new DataInputStream(System.in);

try
{
char inputChar = in.readChar();

while (inputChar != '.')
{
frequencyTable[inputChar-'a'] = frequencyTable[inputChar-'a'] + 1;
inputChar = in.readChar();
}

in.close();
}

catch (IOException e)
{
System.out.println("输入字符有误");
}

for (int i=0;i<26;i++)
{
if (frequencyTable[i] != 0)
{
char c = (char)(97 + i);
System.out.println("字母"+c+"出现次数: "+frequencyTable[i]);
}
}
}
}

[wweijie]

我想问题应该在这里吧
frequencyTable[inputChar-'a'] = frequencyTable[inputChar-'a'] + 1;
你定义的frequencyTable是一个0到25的数组，如果输入的不是'a'-'z'，比如大写'A'或者回车空格之类，inputChar-'a'不就越界了吗？

[fivehun]

我试着输出了一下
System.out.println(inputChar);
得到的不是输入的字符，而是一些汉字，当然越界了，是不是不能使用DataInputStream来读字符呢？

[fivehun]

我刚刚查看了jdk，
the next two bytes of this input stream as a Unicode character
看到readChar(),一次读出了两个字符，所以显示成为了汉字吧！

[kingfish]

既然统计字母就用
byte b = in.readByte();
如果b不在 [a-z][A-Z]范围里就continue;

[casemy]

最好对输入进行下判断

[fivehun]

我找出错误了！
应该用byte
import java.io.*;

public class CalculateFrequency
{
public static void main(String[] args) throws Exception
{
int[] frequencyTable = new int[26];

for (int i=0;i<26;i++)
{
frequencyTable[i] = 0;
}

DataInputStream in = new DataInputStream(System.in);

try
{
byte inputChar = in.readByte();

while (inputChar != '.')
{
frequencyTable[inputChar-'a'] = frequencyTable[inputChar-'a'] + 1;
inputChar = in.readByte();
}


in.close();
}

catch (IOException e)
{
System.out.println("输入字符有误");
}

for (int i=0;i<26;i++)
{
if (frequencyTable[i] != 0)
{
char c = (char)(97 + i);
System.out.println("字母"+c+"出现次数: "+frequencyTable[i]);
}

}
}
}

[ShingU]

谢谢各位,我先看看..:)