how to transform Map to List using google collections

Question

I have a map with strings, I want to transform it to a list of strings with \" \" as a key value separator. Is it possible using google collections?

Code example that I

Answer 1

Here you go:

private static final Joiner JOINER = Joiner.on(' ');
public List mapToList(final Map input){
    return Lists.newArrayList(
        Iterables.transform(
            input.entrySet(), new Function, String>(){
                @Override
                public String apply(final Map.Entry input){
                    return JOINER.join(input.getKey(), input.getValue());
                }
            }));
}

Update: optimized code. Using a Joiner constant should be much faster than String.concat()

---

These days, I would of course do this with Java 8 streams. No external lib needed.

public List mapToList(final Map input) {
    return input.entrySet()
                .stream()
                .map(e -> new StringBuilder(
                             e.getKey().length()
                                     + e.getValue().length()
                                     + 1
                     ).append(e.getKey())
                      .append(' ')
                      .append(e.getValue())
                      .toString()
                )
                .collect(Collectors.toList());
}