Java-8 – Java 8 – maps to comma separated pairs in parentheses

What is the best method in Java 8?

Map<Integer,Integer>

Like a string:

[k1,v1],[k2,v2],[k3,v3]...

I'm looking at something like this, but I don't know how to "return" or "map" StringBuilder:

map.forEach( (k,v) -> s.append("[").append(k).append(",").append(v).append("]") )
                    .collect(Collectors.joining(","));

In any case, I believe StringBuilder is not suitable for parallel multithreading in the future

Note that I can iterate over the map and create all the structures in the old way, but I want to see how to do it with some new Java 8 features

I think some toString () occasionally returns map values in parentheses, which may be convenient, although it's not a good idea to rely on this

Solution

map.entrySet()

map.entrySet()
   .stream()
   .map(e -> "[" + e.getKey() + "," + e.getValue() + "]")
   .collect(Collectors.joining(","));