Is there an elegant way to remove nulls while transforming a Collection using Guava?

problem ：

I have a question about simplifying some Collection handling code, when using Google Collections ( update : Guava ). I have a question about using Google Collections Simplify when Collection Dealing with code problems （ to update ： Guava ）.

I've got a bunch of "Computer" objects, and I want to end up with a Collection of their "resource id"s. I have a bunch “ Computer ” object , I want to finally get them “ resources ID” Set .This is done like so: This is done ：

Collection<Computer> matchingComputers = findComputers();Collection<String> resourceIds =     Lists.newArrayList(Iterables.transform(matchingComputers, new Function<Computer, String>() {    public String apply(Computer from) {        return from.getResourceId();    }}));

Now, getResourceId() may return null (and changing that is not an option right now), yet in this case I'd like to omit nulls from the resulting String collection. Now? , getResourceId() May return to null（ And changing it now is not an option ）, But in this case , I think from the result String Omit from set null.

Here's one way to filter nulls out: This is a way to filter null values ：

Collections2.filter(resourceIds, new Predicate<String>() {    @Override    public boolean apply(String input) {        return input != null;    }});

You could put all that together like this: You can put all these together like this ：

Collection<String> resourceIds = Collections2.filter(Lists.newArrayList(Iterables.transform(matchingComputers, new Function<Computer, String>() {    public String apply(Computer from) {        return from.getResourceId();    }})), new Predicate<String>() {    @Override    public boolean apply(String input) {        return input != null;    }});

But this is hardly elegant, let alone readable, for such a simple task! But this is not elegant for such a simple task , Not to mention readable ！In fact, plain old Java code (with no fancy Predicate or Function stuff at all) would arguably be much cleaner: in fact , Ordinary old Java Code （ There is no fancy Predicate or Function thing ） It can be said that it will be cleaner ：

Collection<String> resourceIds = Lists.newArrayList();for (Computer computer : matchingComputers) {    String resourceId = computer.getResourceId();    if (resourceId != null) {        resourceIds.add(resourceId);    }}

Using the above is certainly also an option, but out of curiosity (and desire to learn more of Google Collections), can you do the exact same thing in some shorter or more elegant way using Google Collections ? Of course, using the above is also an option , But out of curiosity （ And hope to learn more Google Collections）, You can use Google Collections Do exactly the same thing in a shorter or more elegant way Do you ？

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Solution ：

Reference resources ： https://stackoom.com/en/question/7Ywf