protected static boolean isWhiteSpace(char ch) 
{
        // most of the characters are non-control characters.
        // so check that first to quickly return false for most of the cases.
        if( ch >0x20 )   return false;
        // other than we have to do four comparisons.
        return ch == 0x9 || ch == 0xA || ch == 0xD || ch == 0x20;
}

returns true if the specified char is a white space character.

 public String marshal(String s) 
{
        return s;
}

No-op. Just return the same string given as the parameter.

 public String unmarshal(String text) 
{
        if(text==null)  return null;        // be defensive
        int len = text.length();
        // most of the texts are already in the collapsed form.
        // so look for the first whitespace in the hope that we will
        // never see it.
        int s=0;
        while(s< len) {
            if(isWhiteSpace(text.charAt(s)))
                break;
            s++;
        }
        if(s==len)
            // the input happens to be already collapsed.
            return text;
        // we now know that the input contains spaces.
        // let's sit down and do the collapsing normally.
        StringBuffer result = new StringBuffer(len /*allocate enough size to avoid re-allocation*/ );
        if(s!=0) {
            for( int i=0; i< s; i++ )
                result.append(text.charAt(i));
            result.append(' ');
        }
        boolean inStripMode = true;
        for (int i = s+1; i <  len; i++) {
            char ch = text.charAt(i);
            boolean b = isWhiteSpace(ch);
            if (inStripMode && b)
                continue; // skip this character
            inStripMode = b;
            if (inStripMode)
                result.append(' ');
            else
                result.append(ch);
        }
        // remove trailing whitespaces
        len = result.length();
        if (len  > 0 && result.charAt(len - 1) == ' ')
            result.setLength(len - 1);
        // whitespaces are already collapsed,
        // so all we have to do is to remove the last one character
        // if it's a whitespace.
        return result.toString();
}

Removes leading and trailing whitespaces of the string given as the parameter, then truncate any sequnce of tab, CR, LF, and SP by a single whitespace character ' '.