Java syntax with MongoDB

While you can certainly use the form that you suggested:

for (Document document : col.find()) {    // do something}

it introduces a problem when the body of the for loop throws an exception: if this happens the cursor will not be closed. The proper idiom to guard against that is to use MongoCursor (which implements Closeable) explicitly:

try (MongoCursor<Document> cursor = col.find().iterator()) {    while (cursor.hasNext()) {        System.out.println(cursor.next());    }}

The forEach method is just a bit of syntactic sugar to avoid the need for application code to worry about having to close the cursor manually like this.

If you don't want to create a new Block for each iteration, you can refactor your code pull out the anonymous inner class creation, e.g.:

Block<Document> block = new Block<Document>() {    @Override    public void apply(final Document document) {        System.out.println(document);    }};col.find().forEach(block);

Of course that's even clunkier, so if you are able to use Java 8, you can replace the whole thing with a lambda:

col.find().forEach((Block<Document>) document -> {    System.out.println(document);});

or in this case simply:

col.find().forEach((Block<Document>) System.out::println);

The lambda metafactory will ensure that no unnecessary objects are created.

I asked myself the same question and I found pretty easy the following code to handle that situation:

List<Document> restaurants = db.getCollection("restaurants").find().into(new ArrayList<Document>());for (Document restaurant : restaurants) {    System.out.println(restaurant);}