How to write this for loop in Java8 Lambda

Question

Here is my code

String res = "";
    for (int i = 0;i < names.size();i++){
        String name = names.get(i);
        if (!res.equals(""))
                res += ",";
            res += name;
    }

I don't know how to judge wether 'res' equals "" in lambda. Thank you very much if you can help me!

A lambda expression represents an anonymous method (a method without a name) whose signature matches the single method of a functional interface that is being passed to some other method. Where exactly do you think you can place a lambda here? You could however transform the loop into a stream and use some lambda expressions when calling methods in the Stream API. — Seelenvirtuose
– Seelenvirtuose, Commented Mar 23, 2017 at 6:55
Additionally, your code seems to concatenate strings in the list with a joining separator. This can be done with names.stream().collect(Collectors.joining(",")). Without any lambda! — Seelenvirtuose
– Seelenvirtuose, Commented Mar 23, 2017 at 6:57
Being new to Java 8 is no problem. Posting low-quality questions on SO that could have been easily answered by basic learning is, though. — Seelenvirtuose
– Seelenvirtuose, Commented Mar 23, 2017 at 7:07

marc_s · Accepted Answer · 2018-01-16 18:08:03Z

4

I'm not sure a lambda expression is needed here. Did you meant to use the Stream API to refactor your code, as follows?

 String commaSeparatedNames = names.stream()
 .collect(Collectors.joining(", "));

edited Jan 16, 2018 at 18:08

marc_s

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answered Mar 23, 2017 at 6:56

Shmulik Klein

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1 Comment

Seelenvirtuose Over a year ago

Starting an answer with "I'm not sure ..." and "Did you mean ..." usually disqualifies a post as an answer. To get clarification, you should post it as a comment. In fact, the question is indeed unclear.

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