> The simplest optimization would be to create the 'sb' buffer
> at least as big as the 'input' string. After all, even if
> there were no actual substitutions, the 'sb' would be as big,
> and this would avoid StringBuffer doing a lot of
> reallocations, especially if 'input' is more than the 16
> characters, the default capacity of a StringBuffer. This
> could be accomplished with just something like:
Smart, and doesn't require much effort. Does this save a lot of time?
> A more sophisticated optimization would require two loops.
> The first would look very much like the existing loop, but no
> 'sb' StringBuffer would be created until one of the special
> characters was found. The "gamble" is that the string
> contains no characters to be escaped, no extra objects would
> be created. It would look something like:
>
> public static String escapeXml(String input) {
> StringBuffer sb = null;
> int length = input.length();
> int currentPos;
> for (int currentPos = 0; currentPos < length; currentPos++) {
> char c = input.charAt(currentPos);
> if (c == '&') {
> sb = new StringBuffer(length+4);
> sb.append(input.substring(0,currentPos)); //
> copy over the string up until we found this char
> sb.append("&");
> break;
> }
> else if (c == '<') {
>
> sb = new StringBuffer(length+3);
> sb.append(input.substring(0,currentPos)); //
> copy over the string up until we found this char
> sb.append("<");
>
> break;
> }
> else if (c == '>') {
>
> sb = new StringBuffer(length+3);
> sb.append(input.substring(0,currentPos)); //
> copy over the string up until we found this char
> sb.append(">");
>
> break;
> }
> else if (c == '"') {
>
> sb = new StringBuffer(length+5);
> sb.append(input.substring(0,currentPos)); //
> copy over the string up until we found this char
> sb.append(""");
>
> break;
> }
> else if (c == '\'') {
>
> sb = new StringBuffer(length+5);
> sb.append(input.substring(0,currentPos)); //
> copy over the string up until we found this char
> sb.append("'");
>
> break;
> }
>
> }
>
> // If we didn't create a new buffer, then the input
> string didn't need any escaping so we win big time
> // and we can just return the same string they gave
> us (no object creation, no copying).
> if ( sb == null )
> return input;
>
> // Oh well, we did have some escaping to do, so let's
> check the rest to see if there are any more to do.
> for ( ++currentPos; currentPos < length; ++currentPos) {
> char c = input.charAt(currentPos);
> if (c == '&')
> sb.append("&");
> else if (c == '<')
> sb.append("<");
> else if (c == '>')
> sb.append(">");
> else if (c == '"')
> sb.append(""");
> else if (c == '\'')
> sb.append("'");
> else
> sb.append(c);
> }
> return sb.toString();
> }
Try it simpler:
public static String escapeXml(String input) {
StringBuffer sb = null;
int length = input.length();
int currentPos;
//Check if there are any special characters to escape
for (currentPos = 0; currentPos < length; currentPos++) {
char c = input.charAt(currentPos);
if (c == '&' || c == '<' || c == '>' || c == '"' || c ==
'\'') {
sb = new StringBuffer(length);
sb.append(input.substring(0,currentPos)); // copy over
the string up until we found this char
break;
}
}
// If we didn't create a new buffer, then the input string
didn't need any escaping so we win big time
// and we can just return the same string they gave us (no
object creation, no copying).
if ( sb == null )
return input;
// Oh well, we did have some escaping to do, so let's check the
rest to see if there are any more to do.
for (; currentPos < length;++currentPos) {
char c = input.charAt(currentPos);
if (c == '&')
sb.append("&");
else if (c == '<')
sb.append("<");
else if (c == '>')
sb.append(">");
else if (c == '"')
sb.append(""");
else if (c == '\'')
sb.append("'");
else
sb.append(c);
}
return sb.toString();
}
Martin
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