new StringBuilder(char)

Eddie Aftandilian eaftan at
Fri Aug 8 20:53:59 UTC 2014

Hi all,

We recently realized that calling new StringBuilder(char) does not do what
you would think it does.  Since there is no char constructor defined, the
char is widened to an int and the StringBuffer is presized to the
character's encoded value.  Thus code like this prints an empty string
rather than the expected "a":
System.out.println(new StringBuilder('a'));

Would it be possible to add a char constructor to StringBuilder to prevent
this problem? I understand this would change the behavior of any code that
is currently doing this, but it's hard to imagine anyone doing this
intentionally.  Of the ~20 instances we found in Google's codebase, all
were bugs.  What is your policy on making changes like this where (a) it
will cause a change in behavior, but (b) the currently behavior is clearly

If you're willing to take the change, I'd be happy to send a patch.


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