StringBuilder - 重置或创建新的 [英] StringBuilder - Reset or create a new

问题描述

我有一个条件，StringBuilder保持存储与大平面文件（100的MB）中的模式匹配的行。但是在达到条件后，我将StringBuilder varialble的内容写入文本文件。

I have a condition that a StringBuilder keeps storing lines matching a pattern from a large flat file (100's of MB). However after reaching a condition I write the content of the StringBuilder varialble to a textfile.

现在我想知道是否应该通过重置对象来使用相同的变量 - >

Now I wonder if I should use the same variable by resetting the object ->

stringBuilder.delete(0,stringBuilder.length())

OR

stringBuilder=new StringBuilder();

请注意，就性能和OOM问题而言，您认为哪种方式更好。

Please suggest which would do you think is better as far as both performance and OOM issues are concerned.

推荐答案

我认为 StringBuilder #delete（start，end）仍然很贵请致电：

I think StringBuilder#delete(start, end) is still expensive call, you should do:

stringBuilder.setLength(0);

重置它。

更新：查看 源代码 StringBuilder 似乎 setLength（int）保留旧缓冲区，最好调用： StringBuilder＃trimToSize（） 在上述通话后 尝试减少用于字符序列的存储空间 。

UPDATE: After looking at source code of StringBuilder It seems setLength(int) leaves old buffer intact and it is better to call: StringBuilder#trimToSize() after above call which attempts to reduce storage used for the character sequence.

所以这样的事情会更有效率：

So something like this would be more efficient:

stringBuilder.setLength(0); // set length of buffer to 0
stringBuilder.trimToSize(); // trim the underlying buffer

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