字符串的ArrayList为一个字符串 [英] ArrayList of Strings to one single string

问题描述

我有一个字符串数组列表（数组列表中的每个单独元素只是一个没有空格的单词），我想取每个元素并将每个下一个单词追加到字符串的末尾。

I have an array list of strings (each individual element in the array list is just a word with no white space) and i want to take each element and append each next word to the end of a string.

所以说数组列表有

    element 0 = "hello"
    element 1 = "world,"
    element 2 = "how"
    element 3 = "are"
    element 4 = "you?"

我想创建一个名为句子的字符串，其中包含hello world，你好吗？

I want to make a string called sentence that contains "hello world, how are you?"

推荐答案

从Java 8开始，这已被添加到标准Java API中：

As of Java 8, this has been added to the standard Java API:

String.join（）方法：

String.join() methods:

String joined = String.join("/", "2014", "10", "28" ); // "2014/10/28"

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

StringJoiner ：

StringJoiner is also added:

StringJoiner joiner = new StringJoiner(",");
joiner.add("foo");
joiner.add("bar");
joiner.add("baz");
String joined = joiner.toString(); // "foo,bar,baz"

另外，它是nullsafe，我很欣赏。这样，我的意思是如果 StringJoiner 在列表中遇到 null ，它不会抛出NPE：

Plus, it's nullsafe, which I appreciate. By this, I mean if StringJoiner encounters a null in a List, it won't throw a NPE:

@Test
public void showNullInStringJoiner() {
    StringJoiner joinedErrors = new StringJoiner("|");
    List<String> errorList = Arrays.asList("asdf", "bdfs", null, "das");
    for (String desc : errorList) {
        joinedErrors.add(desc);
    }

    assertEquals("asdf|bdfs|null|das", joinedErrors.toString());
}

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