Question

I was looking through the source code of this class and I start from append method that is called by StringBUffer.append();

public AbstractStringBuilder append(String str) {
   if (str == null) str = "null";
       int len = str.length();
   if (len == 0) return this;
   int newCount = count + len;
   if (newCount > value.length)
      expandCapacity(newCount); // newcount is the new volumn of a char array
    str.getChars(0, len, value, count);
    count = newCount;
    return this;
  }

Then I went deeper into enpandCapacity method

void expandCapacity(int minimumCapacity) {
    int newCapacity = (value.length + 1) * 2; //here value is a char array 
    if (newCapacity < 0) { // Why is newCapacity less than 0?
                           // Is that possible? When it will be possible?
        newCapacity = Integer.MAX_VALUE;
    } else if (minimumCapacity > newCapacity) {
        newCapacity = minimumCapacity;
    }
    value = Arrays.copyOf(value, newCapacity);
}

Why is newCapacity less than 0? Is that possible? When it will be possible?

Answer 1

Yes; signed integers can become negative once the max value of the int type (2^31 – 1) is exceeded. If you take a look, they are essentially capping the capacity at Integer.MAX_VALUE. Similar type of question here.