Question

我认为有人已经问过这个问题但仍然存在。

我有随机字符串值的ArrayList，我需要将这些值放入另一个ArrayList，但只能放在一个索引中。

示例：

我有

{ "hey","how","are","you"}

我需要做到

{"Hey how are you"}

是否有像join或smth这样的命令？因为我尝试将另一个String值添加到同一个索引中，但它只替换了它。

Answer 1

您可以将StringJoiner用于该解决方案。

List<String> mainList = new ArrayList<>();  //The one to contain all Strings from yourList
List<String> yourList = Arrays.asList("Hey", "how", "are", "you");    //The list of Strings

StringJoiner joiner = new StringJoiner(" "); //Space as delimiter, strings will be separated with spaces
for (String s : yourlist) {
    joiner.add(s);
}
mainList.add(joiner.toString());    //Add the new concatenated String to your list, in a single string

Answer 2

Java 8添加了一个StringJoiner类，它完全符合您的要求（以下代码在Java 9中）：

    List<String> list = List.of("hey", "how", "are", "you");
    StringJoiner joiner = new StringJoiner(" ");
    list.forEach(str -> joiner.add(str));
    System.out.println(joiner.toString()); // hey how are you
    // and if you want the final result to be in a list
    // Java 9:
    list = List.of(joiner.toString());
    // anything before Java 9
    list = Arrays.asList(joiner.toString());

另一种（更简单）的方法（自Java 8起）：

String.join(" ", list)

Answer 3

使用StringBuilder加入多个字符串

StringBuilder sb = new StringBuilder();
listA.forEach(item -> sb.append(item));

listB.add(sb.toString());

Answer 4

commons.lang3.StringUtils

StringUtils.join（Object array []，String separator）

https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html

Answer 5

一个解决方案就像：

List<String> result = new ArrayList<>(Arrays.asList(myList.stream().collect(Collectors.joining(" "))));

数组列表。在一个索引中连接String值

5 个答案: