java - StringBuilder容量()

Question

我注意到 capacity 方法在没有逻辑的情况下返回 StringBuilder capacity方式...有时它的值等于字符串长度其他时间它更大...

是否有一个等式可以知道它的逻辑是什么？

Answer 1

当您附加到 StringBuilder 时，会发生以下逻辑:

if (newCount > value.length) {
    expandCapacity(newCount);
}

其中 newCount 是所需的字符数，value.length 是缓冲区的当前大小。

expandCapacity 只是增加后备 char[]

的大小

ensureCapacity() 方法是调用 expandCapacity() 的公共(public)方法，它的文档说:

Ensures that the capacity is at least equal to the specified minimum. If the current capacity is less than the argument, then a new internal array is allocated with greater capacity. The new capacity is the larger of:

• The minimumCapacity argument.
• Twice the old capacity, plus 2.

If the minimumCapacity argument is nonpositive, this method takes no action and simply returns.