字符串正则化类
public class StringNormalize {
public static String normalize(String in) {
StringBuilder out = new StringBuilder();
String l = in.toLowerCase();
for (int i = 0; i < l.length(); ++i) {
char c = l.charAt(i);
if (c >= 'a' && c <= 'z' || c >= '0' && c <= '9') {
out.append(c);
}
}
return out.toString();
}
}