How to access objects outside of a lambda inside forEach?

I have the following code:

String fields = "";
listofObjects.stream().forEach(l -> fields = fields + l.text);

Which doesn't work, because fields should be final. How can I modify fields using lambdas?

The smallest change to make that work would just be to use a StringBuilder instead - and that would be more efficient:

StringBuilder builder = new StringBuilder();
listofObjects.stream().forEach(l -> builder.append(l.text));
String fields = builder.toString();

As Martin notes, Collectors.joining() provides general string joining capabilities, but you need to map your stream of objects to a stream of strings first. (Easy to do with map, and if you need to do this very often you could always create your own collector to do that.)

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