StringBuffer capacity

[Vicken Karaoghlanian]

class Test {

public static void main(String args[]) {
StringBuffer ss = new StringBuffer("1234567890123456"); // line 1
StringBuffer s = new StringBuffer("12345");  // line 2
s.append(ss);  // line 3
System.out.println(s.capacity());  // line 4
}
}

1) on line 2, a string buffer (s) of capacity 16 + 5 = 21 is created.
2) on line 3, we appended ss to s making 16 + 5 = 21, which fits perfectly in s, making the output on line 4 equals to 21.
my question is: if we add another character to ss

StringBuffer ss = new StringBuffer("12345678901234567");

the output (capcity) of s becomes 44 !!! isn't suppose that the capacity increases by one, hence becoming 22??

[Miki Muzsi]

when using append() for a StringBuffer, the ensureCapacity() method is implicitly called. See JLS1 - StringBuffer
Miki