JAVA

java stream add to existing list

List<String> source = ...;
List<Integer> target = ...;

source.stream()
      .map(String::length)
      .forEachOrdered(target::add);

java 8 stream add to list

List<String> destList = Arrays.asList("foo");
List<String> newList = Arrays.asList("0", "1", "2", "3", "4", "5");

destList = Stream.concat(destList.stream(), newList.stream()).parallel()
            .collect(Collectors.toList());
System.out.println(destList);

//output: [foo, 0, 1, 2, 3, 4, 5]