番石榴乔伊纳没有前缀和后缀的能力 [英] Guava Joiner doesn't have ability to prefix and suffix

问题描述

例如

  String str [] = {a，b，c}; 
 Joiner.on（，）。prefix（'）。suffix（'）。join（str）; 
  

---

预期输出为：

 'a'，'b'，'c'
  

我们有其他的选择吗？由于番石榴不这样做（或我不知道）。使用java 8有更好的选择吗？

解决方案

您可以使用Guava的 List＃transform 进行转换 a - > 'a'，然后在转换的列表上使用 Joiner 。 transform 只适用于 Iterable 对象，但不适用于数组。代码仍然很简洁：

  List< String> strList = Lists.newArraylist（str）; // where str is your String [] 
 Joiner.on（'，'）。join（Lists.transform（str，surroundWithSingleQuotes））; 
  

其中转换如下：

 函数< String，String> surroundWithSingleQuotes = new Function< String，String>（）{
 public String apply（String string）{
 return'+ string +'; 
} 
}; 
  

有人可能会说这是一种啰嗦的做法，但我很佩服灵活性由 transform 范例提供。

编辑（因为现在有Java 8）

在Java 8中，所有这些都可以使用

  strList.stream（）。map（s  - >'+ s +'）.collect（Collectors.joining（，））; 
  

I have requirement in Joiner to have the ability to prefix and suffix elements.

For example

String str[] = {"a", "b", "c"};
Joiner.on(",").prefix("'").suffix("'").join(str);

---

Expected output would be:

'a','b','c'

Do we have any alternative for this? As Guava doesn't do it (or I'm not aware of). With java 8 is there a better alternative?

解决方案

You can use Guava's List#transform to make the transformation a --> 'a' and then use Joiner on the transformed list. transform only works on Iterable objects, though, not on arrays. The code will still be succinct enough:

List<String> strList = Lists.newArraylist(str); // where str is your String[]
Joiner.on(',').join(Lists.transform(str, surroundWithSingleQuotes));

where the transformation is as follows:

Function<String, String> surroundWithSingleQuotes = new Function<String, String>() {
    public String apply(String string) {
        return "'" + string + "'";
    }
};

One might say this is a long-winded way of doing this, but I admire the amount of flexibility provided by the transform paradigm.

Edit (because now there's Java 8)

In Java 8, all this can be done in a single line using the Stream interface, as follows:

strList.stream().map(s -> "'" + s + "'").collect(Collectors.joining(","));

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