/** Demo of alternate methods for sanitizing a string */
public class SanitaryString
{
    /* Uses no data structure */
    private static String bonehead(String suspect)
    {
        StringBuffer result = new StringBuffer();
	// Examine each character in the suspect string
        for (int i=0; i<suspect.length(); i++)
        {
    	    char current = suspect.charAt(i);
                // Is the character allowed?
    	    if (current >= 'a' && current <= 'z' ||
    	        current >= 'A' && current <= 'Z' ||
    		current >= '0' && current <= '9' ||
    		current == '.' || current == '_')
    	    {
    		 result.append(current);
    	    }
    	}
        return result.toString();
    }

    /* Uses a linear search: indexOf() */
    private static String sanitize(String suspect)
    {
       // allow alphanumerics or period or underline
       final String kAllowedCharacters = "abcdefghijklmnopqrstuvwxyz"
        + "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "0123456789" + "._";

        StringBuffer result = new StringBuffer();
        // Examine each character in the suspect string
        for (int i=0; i<suspect.length(); i++)
        {
            char current = suspect.charAt(i);
            // Is the character allowed?
            if (kAllowedCharacters.indexOf(current) >= 0)
            {
                result.append(current);
            }
        }
        return result.toString();
    }

    // Uses a lookup table (for ASCII characters)
    private static String lookup(String suspect)
    {
       // allow alphanumerics or period or underline
       final boolean[] kAllowedCharacters = 
       {
           false,false,false,false,false,false,false,false,false,false,
           false,false,false,false,false,false,false,false,false,false,
           false,false,false,false,false,false,false,false,false,false,
           false,false,false,false,false,false,false,false,false,false,
         //                                      .           0     1
           false,false,false,false,false,false,true, false,true, true, 
         //  2     3     4     5     6     7     8     9
           true, true, true, true, true, true, true, true, false,false,
         //                                A     B     C     D     E
           false,false,false,false,false,true, true, true, true, true, 
         //  F     G     H     I     J     K     L     M     N     O
           true, true, true, true, true, true, true, true, true, true, 
         //  P     Q     R     S     T     U     V     W     X     Y
           true, true ,true ,true ,true ,true ,true ,true, true, true, 
         //  Z                             _           a     b     c
           true, false,false,false,false,true, false,true, true, true, 
         //  d     e     f     g     h     i     j     k     l     m
           true, true, true, true, true, true, true, true, true, true, 
         //  n     o     p     q     r     s     t     u     v     w 
           true, true, true, true, true, true, true, true, true, true, 
         //  x     y     z                                
           true, true, true, false,false,false,false,false
        };

        StringBuffer result = new StringBuffer();
        // Examine each character in the suspect string
        for (int i=0; i<suspect.length(); i++)
        {
            // The character becomes the lookup table index
            int current = (int) suspect.charAt(i);
            // Is the character allowed?
            if (kAllowedCharacters[current])
            {
                result.append(suspect.charAt(i));
            }
        }
        return result.toString();
    }

    public static void main(String args[])
    {
	System.out.println(SanitaryString.bonehead("AHZ$aez@[^{!*+-&/:01239_."));
	System.out.println(SanitaryString.sanitize("AHZ$aez@[^{!*+-&/:01239_."));
	System.out.println(SanitaryString.lookup("AHZ$aez@[^{!*+-&/:01239_."));
    }
}