问题描述
我打算对StringBuilders中的最后一个字符进行很多删除.对我来说，使用sb.setLength(sb.length() - 1);的解决方案看起来不错.但是，由于这些删除将处于循环中，因此我需要知道其复杂性.
I'm planning to perform lots of deletes of the last character in StringBuilders. The solution to use sb.setLength(sb.length() - 1); looks good to me. However, since these deletions will be in a loop, I need to know complexity of it.
据我所知，此操作只是减少StringBuilder对象的一些私有属性，并且不对字符本身执行任何复制/克隆/复制操作，因此它的时间为O(1)，应该可以快速运行.
The way I understand it is that this operation simply decrements some private attribute of my StringBuilder object and does not perform any copying/cloning/duplicating of the characters themselves, thus it is O(1) in time and should work fast.
我说得对吗?
推荐答案
来自文档:
newLength参数必须大于或等于0.
The newLength argument must be greater than or equal to 0.
我会说是的.但是从时间复杂度的角度来看，我不会看到它.我们在循环中使用StringBuilder而不是String的原因是因为String是不可变的.因此，当我们尝试更改它时，将始终创建一个新的字符串对象.更改StringBuilder对象的长度时，不会创建新对象.
I would say yes. But I wouldn't see it from the point of view of time complexity. The reason we use StringBuilder instead of String in a loop is because Strings are immutable. Hence a new string object will always be created when we try to change it. When you change the length of a StringBuilder object, no new object is created.
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