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https://issues.apache.org/jira/browse/LANG-604?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12848141#action_12848141
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Kai Gülzau commented on LANG-604:
---------------------------------
Ok, good point. This way you don't loose performance for trimmed strings.
But the loop doesn't check all chars now:
isBlank(" X ") returns true!
There are two fixes:
a)
...
for (int m = strLen / 2, i = 1; m < strLen; m++, i++) {
...
Here one char (at strLen / 2) is double checked for even length blank strings.
b)
...
int mid = strLen / 2;
for (int i = 1, m = mid; m < strLen; m++, i++) {
if (!Character.isWhitespace(cs.charAt(m)) || ( i < mid &&
!Character.isWhitespace(cs.charAt(i))) ) {
...
Here we loose some minor performance on very large blank strings due
to the extra check in the loop.
I opt for b).
Kai
> Optimize isBlank() for untrimmed strings
> ----------------------------------------
>
> Key: LANG-604
> URL: https://issues.apache.org/jira/browse/LANG-604
> Project: Commons Lang
> Issue Type: Improvement
> Components: lang.*
> Affects Versions: 3.0
> Reporter: Kai Gülzau
> Priority: Minor
>
> Change isBlank() to start iteration in the middle of the String.
> So you get better performance for untrimmed Strings like " dummy ".
> Here is my proposal:
> public static boolean isBlank(CharSequence cs) {
> int strLen;
> if (cs == null || (strLen = cs.length()) == 0) {
> return true;
> }
> int mid = strLen / 2, i = mid;
> for (; i < strLen; i++) {
> if (!Character.isWhitespace(cs.charAt(i))) {
> return false;
> }
> }
> for (i = 0; i < mid; i++) {
> if (!Character.isWhitespace(cs.charAt(i))) {
> return false;
> }
> }
> return true;
> }
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