java - AbstractStringBuilder 类中的 expandCapacity 方法

Question

我正在查看此类的源代码，我从 StringBUffer.append(); 调用的 append 方法开始

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;
  }

然后我深入研究了enpandCapacity方法

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);
}

为什么 newCapacity 小于 0？那可能吗？什么时候可以？

Answer 1

是的；一旦超过 int 类型的最大值 (2^31 - 1)，有符号整数可能会变为负数。如果您看一下，它们实际上是将容量限制在 Integer.MAX_VALUE。同类问题here .