将整数列表转换为逗号分隔的字符串? [英] Convert list of integer into comma separated string?

问题描述

我试图将整数列表转换为用逗号分隔的整数组成的字符串.

I was trying to convert list of Integers into String of comma separated integers.

Collectors.joining(CharSequence delimiter)-返回一个收集器，该收集器以相遇顺序连接由指定分隔符分隔的输入元素.

List<Integer> i = new ArrayList<>();    //  i.add(null);
for (int j = 1; j < 6; j++) {
    i.add(j);
}
System.out.println(i.stream().collect(Collectors.joining(","))); // Line 8

第8行出现错误.

Java 8中的流有没有办法做到这一点?

Is there any way to do this by streams in Java 8?

更新:

如果我用"1"，"2"，"3"，"4"，"5" 创建一个字符串列表.可以.

If i create a list of string with "1", "2", "3","4","5". it works.

推荐答案

是.但是，对于 Stream< Integer> ，没有 Collectors.joining ；您需要一个 Stream< String> ，因此您应先 map 进行收集.像

Yes. However, there is no Collectors.joining for a Stream<Integer>; you need a Stream<String> so you should map before collecting. Something like,

System.out.println(i.stream().map(String::valueOf)
        .collect(Collectors.joining(",")));

哪个输出

1,2,3,4,5

此外，您可以通过多种方式生成 Stream< Integer> .

Also, you could generate Stream<Integer> in a number of ways.

System.out.println(
        IntStream.range(1, 6).boxed().map(String::valueOf)
               .collect(Collectors.joining(","))
);

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