问题

我有一系列的对象：

List<Obj> objList = [obj1, obj2]

obj1.val = "val1";
obj2.val = "val2";

我想要使用“.”作为分隔符，将这些对象的字符串参数连接起来。我尝试使用流进行连接：

objList.stream().collect(Collectors.joining("."));

但我无法弄清楚如何仅连接对象的参数。

在这种情况下，结果应为“val1.val2”。

英文:

I have list of objects:

List&lt;Obj&gt; objList = [obj1, obj2]

obj1.val = &quot;val1&quot;
obj2.val = &quot;val2&quot;

And I want to concat String parameters from that objects with "." separator.
I tried to concatenate them with stream :

objList.stream().collect(Collectors.joining(&quot;.&quot;));

But I can't figure it out how to concat only parameters from objects.

In this case the result should be "val1.val2"

答案1

得分: 0

你在这里缺少了 map 操作符。你需要在收集之前的流处理流程中添加 map 操作符。下面是示例代码：

objList.stream().map(Obj::val).collect(Collectors.joining("."));

英文:

You are missing the map operator here. You have to add map operator to the stream processing pipeline before collecting it. Here's how it looks.

objList.stream().map(Obj::val).collect(Collectors.joining(&quot;.&quot;));

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