放置 set 内容的最快方法到单个字符串，单词由空格分隔?-尊龙凯时

问题描述

我有几个 set 并希望将它们中的每一个转换为单个 string，其中原始 set 由空格"分隔.一个天真的第一种方法是这样做

i have a few sets and want to transform each of these into a single string where each element of the original set is separated by a whitespace " ". a naive first approach is doing it like this

set set_1;
set set_2;
stringbuilder builder = new stringbuilder();
for (string str : set_1) {
  builder.append(str).append(" ");
}
this.string_1 = builder.tostring();
builder = new stringbuilder();
for (string str : set_2) {
  builder.append(str).append(" ");
}
this.string_2 = builder.tostring();

谁能想到一种更快、更漂亮或更有效的方法来做到这一点?

can anyone think of a faster, prettier or more efficient way to do this?

推荐答案

使用 commons/lang 你可以使用 stringutils.join:

string str_1 = stringutils.join(set_1, " ");

为了简洁，你无法真正击败它.

you can't really beat that for brevity.

更新:

重新阅读这个答案，我现在更喜欢关于番石榴木匠的其他答案.事实上，这些天我并没有靠近 apache commons.

re-reading this answer, i would prefer the other answer regarding guava's joiner now. in fact, these days i don't go near apache commons.

另一个更新:

java 8 引入了方法 string.join()

java 8 introduced the method string.join()

string joined = string.join(",", set);

虽然这不如 guava 版本灵活，但当您的类路径中没有 guava 库时，它会很方便.

while this isn't as flexible as the guava version, it's handy when you don't have the guava library on your classpath.