Once you have instantiated an OSLC client, you can use the GetCollection class to request the content of a DOORS Next Collection.
OslcClient client = OslcClients.jazzForm(new UsernamePasswordCredentials("myUser", "myPassword")).create();
URI collectionUri = URI.create("https://myServer:9443/rm/myCollection");
DngCollection collection = new GetCollection(client, collectionUri).get();
System.out.println("Title: " + collection.getTitle());
System.out.println("Identifier: " + collection.getIdentifier());
System.out.println("Uses: ");
for (URI requirementUri : collection.getUses()) {
System.out.println("- " + requirementUri);
}

Creating an OSLC client
Querying OSLC Resources
Using OSLC Configurations
Adding a Requirement in a Collection