Closing over immutable variable and accumulate values across multiple iterations as a lambda expression - Java 8

Question

WebTarget in Jersey client is implemented as a immutable object, and any operations to change the state returns a new WebTarget. To add query params to it, which is coming in as

Answer 1

If you want functional approach you need foldLeft(right) or reduce.

foldLeft is implemented in some libraries, for example Functionaljava and streamEx.

Functionaljava:

 B foldLeft(final F> bff, final B z)

WebTarget wt = wtCollection.foldLeft(x -> (y -> x.queryParam(...)), new WebTarget());

StreamEx:

 U foldLeft(U seed, BiFunction accumulator) 

UPD stream-reduce

queryMap.entrySet().stream()
    .reduce(new WebTarget(), (x, y) -> { 
        x.queryParam(y.getKey(), y.getValue()); 
    });