String.toCharArray（）的运行时间是多少？ [英] What is the run time of String.toCharArray()?

问题描述

在 String.toCharArray（）中的运行时间是什么？源代码是

What's the run time of String.toCharArray() in java? The source code is

 public char[] toCharArray() {
    // Cannot use Arrays.copyOf because of class initialization order issues
    char result[] = new char[value.length];
    System.arraycopy(value, 0, result, 0, value.length);
    return result;
}

System.arrayCopy ？有运行时间O（n）？源代码并没有真正说明它是如何实现的。它是否通过每个元素并复制它？谢谢。

Does System.arrayCopy? have run time of O(n)? The source code doesn't really say much about how it's implemented. Does it go through every element and copies it? Thanks.

推荐答案

System.arraycopy（）快速。也就是说，它仍然需要查看（和复制）数组的每个元素，所以其渐近复杂性在数组的长度是线性的，即 O（n） 。

System.arraycopy() is typically an intrinsic and is very fast. That said, it still has to look at (and copy) every element of the array, so its asymptotic complexity is linear in the length of the array, i.e. O(n).

因此 toCharArray（）的复杂度为 O（n），其中 n 是字符串的长度。

Thus the complexity of toCharArray() is O(n), where n is the length of the string.

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