判定为英文

char c = 'a';if(c>='a'&&c<='z'||c>='A'&&c<='Z'){    // TODO}

class MyCharacter implements CharSequence {    char target;    public char charAt(int arg0) {        return target;    }    public int length() {        if (target == '\u0000') {            return 0;        }        return 1;    }    public CharSequence subSequence(int arg0, int arg1) {       return null;    }    public MyCharacter(char c) {       this.target = c;    }}Pattern.matches("[a-zA-Z]", new MyCharacter('a'));

根据其ascii 值判断。如果字符的值在65到90之间或者在97到122之间就是字母

：#include

isalnum() 用来判断一个字符是否为英文字母或数字，相当于 isalpha(c) || isdigit(c)，其原型为：

int isalnum(int c);

【参数】c 为需要检测的字符。

【返回值】若参数c 为字母或数字，若 c 为 0 ~ 9  a ~ z  A ~ Z 则返回非 0，否则返回 0。注意，isalnum()为宏定义，非真正函数。

【实例】找出str 字符串中为英文字母或数字的字符。

#include main(){char str[] = "123c@#FDsP[e?";int i;for (i = 0; str[i] != 0;

i++)if(isalnum(str[i]))printf("%c is an alphanumeric character\n", str[i]);}

#include

main(){

char str[] = "123c@#FDsP[e?";

int i;

for (i = 0; str[i] != 0; i++)

if(isalnum(str[i]))

printf("%c is an alphanumeric character\n", str[i]);}

输出结果：1 is an apphabetic character

2 is an apphabetic character

3 is an apphabetic character

c is an apphabetic character

F is an apphabetic character

D is an apphabetic character

s is an apphabetic character

P is an apphabetic character

e is an apphabetic character