Convert an loop (while and for) to stream

Question

I have started working with Java 8 and trying to convert some loops and old syntax in my code to lambdas and streams.

So for example, I\'m trying to convert this whi

Answer 1

You can achieve it with a stream nested in a stream created from oldList list. Nested stream plays role of mapping current value from oldList with a mapper defined in map, e.g.

public static void main(String[] args) {
    final List oldList = Arrays.asList("asd-qwe", "zxc", "123");
    final Map map = new HashMap() {{
        put("asd", "zcx");
        put("12", "09");
        put("qq", "aa");
    }};

    List result = oldList.stream()
            .map(line -> map.entrySet()
                    .stream()
                    .filter(entry -> line.startsWith(entry.getKey()))
                    .map(entry -> line.replace(entry.getKey(), entry.getValue()))
                    .collect(Collectors.toList())
            )
            .flatMap(Collection::stream)
            .collect(Collectors.toList());


    System.out.println(result);
}

Following example produces output like:

[zcx-qwe, 093]

Suggested solution can be easily parallelized if needed. Functional approach with no side effects.