固定数组？/ StringBuilder？/字符串？如果要追加84个字符串，这是创建字符串的最佳方法

问题描述

我事先知道，将有84个字符串要用逗号分隔符追加，然后创建一个字符串，

I know in advance that, there would be 84 strings going to be appended by comma separator, to create one string then,

哪种方法最好是固定的数组，字符串还是字符串生成器？

Which way is be better a fixed Array, Strings or String Builder?

推荐答案

如果用最佳表示内存和/或运行时效率最高，那么您最好使用预先分配的 StringBuilder 。 （在JDK中研究了 String.join 的实现，它使用了 StringJoiner ，后者使用了 StringBuilder ，其默认初始容量为[16个字符]，并且不尝试避免重新分配和复制。）

If by "best" you mean "most memory and/or runtime efficient" then you're probably best off with a StringBuilder you pre-allocate. (Having looked at the implementation of String.join in the JDK, it uses StringJoiner, which uses a StringBuilder with the default initial capacity [16 chars] with no attempt to avoid reallocation and copying.)

您总结了一下84个字符串的长度，添加逗号数，创建具有该长度的 StringBuilder ，全部添加，然后调用 toString 就可以了。例如：

You'd sum up the lengths of your 84 strings, add in the number of commas, create a StringBuilder with that length, add them all, and call toString on it. E.g.:

int length = 0;
for (int i = 0; i < strings.length; ++i) {
    length += strings[i].length();
}
length += strings.length - 1; // For the commas
StringBuilder sb = new StringBuilder(length);
sb.append(strings[0]);
for (int i = 1; i < strings.length; ++i) {
    sb.append(',');
    sb.append(strings[i]);
}
String result = sb.toString();

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