Java：转换List< String>到一个字符串 [英] Java: convert List<String> to a String

问题描述

JavaScript已 Array.join（）

JavaScript has Array.join()

js>["Bill","Bob","Steve"].join(" and ")
Bill and Bob and Steve

Java有这样的东西吗？我知道我可以用StringBuilder自行解决一些问题：

Does Java have anything like this? I know I can cobble something up myself with StringBuilder:

static public String join(List<String> list, String conjunction)
{
   StringBuilder sb = new StringBuilder();
   boolean first = true;
   for (String item : list)
   {
      if (first)
         first = false;
      else
         sb.append(conjunction);
      sb.append(item);
   }
   return sb.toString();
}

...但如果类似的话已经没有意义了JDK的一部分。

...but there's no point in doing this if something like it is already part of the JDK.

推荐答案

使用Java 8，您可以在没有任何第三方库的情况下执行此操作。

With Java 8 you can do this without any third party library.

如果你想加入一个字符串集合，你可以使用新的 String.join（）方法：

If you want to join a Collection of Strings you can use the new String.join() method:

List<String> list = Arrays.asList("foo", "bar", "baz");
String joined = String.join(" and ", list); // "foo and bar and baz"

如果你有一个其他类型而不是String的Collection，你可以使用Stream API与加入收藏家：

If you have a Collection with another type than String you can use the Stream API with the joining Collector:

List<Person> list = Arrays.asList(
  new Person("John", "Smith"),
  new Person("Anna", "Martinez"),
  new Person("Paul", "Watson ")
);

String joinedFirstNames = list.stream()
  .map(Person::getFirstName)
  .collect(Collectors.joining(", ")); // "John, Anna, Paul"

StringJoiner 类也可能有用。

The StringJoiner class may also be useful.

这篇关于Java：转换List< String>到一个字符串的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！