GUAC-1170: Use checked versions of empty list/set/map.

guacamole-ext/src/main/java/org/glyptodon/guacamole/net/auth/credentials/CredentialsInfo.java

@@ -65,7 +65,7 @@ public class CredentialsInfo {
      * CredentialsInfo object which describes empty credentials. No parameters
      * are required.
      */
-    public static final CredentialsInfo EMPTY = new CredentialsInfo(Collections.EMPTY_LIST);
+    public static final CredentialsInfo EMPTY = new CredentialsInfo(Collections.<Parameter>emptyList());
 
     /**
      * CredentialsInfo object which describes standard username/password

guacamole-ext/src/main/java/org/glyptodon/guacamole/net/auth/simple/SimpleConnection.java

@@ -117,7 +117,7 @@ public class SimpleConnection extends AbstractConnection {
 
     @Override
     public List<ConnectionRecord> getHistory() throws GuacamoleException {
-        return Collections.EMPTY_LIST;
+        return Collections.<ConnectionRecord>emptyList();
     }
 
 }

guacamole-ext/src/main/java/org/glyptodon/guacamole/net/auth/simple/SimpleDirectory.java

@@ -45,7 +45,7 @@ public class SimpleDirectory<ObjectType> implements Directory<ObjectType> {
     /**
      * The Map of objects to provide access to.
      */
-    private Map<String, ObjectType> objects = Collections.EMPTY_MAP;
+    private Map<String, ObjectType> objects = Collections.<String, ObjectType>emptyMap();
 
     /**
      * Creates a new empty SimpleDirectory which does not provide access to

guacamole-ext/src/main/java/org/glyptodon/guacamole/net/auth/simple/SimpleObjectPermissionSet.java

@@ -42,7 +42,7 @@ public class SimpleObjectPermissionSet implements ObjectPermissionSet {
     /**
      * The set of all permissions currently granted.
      */
-    private Set<ObjectPermission> permissions = Collections.EMPTY_SET;
+    private Set<ObjectPermission> permissions = Collections.<ObjectPermission>emptySet();
 
     /**
      * Creates a new empty SimpleObjectPermissionSet.

guacamole-ext/src/main/java/org/glyptodon/guacamole/net/auth/simple/SimpleSystemPermissionSet.java

@@ -40,7 +40,7 @@ public class SimpleSystemPermissionSet implements SystemPermissionSet {
     /**
      * The set of all permissions currently granted.
      */
-    private Set<SystemPermission> permissions = Collections.EMPTY_SET;
+    private Set<SystemPermission> permissions = Collections.<SystemPermission>emptySet();
 
     /**
      * Creates a new empty SimpleSystemPermissionSet.

guacamole-ext/src/main/java/org/glyptodon/guacamole/net/auth/simple/SimpleUserContext.java

@@ -126,7 +126,7 @@ public class SimpleUserContext implements UserContext {
         // Add root group that contains only the given configurations
         this.rootGroup = new SimpleConnectionGroup(
             ROOT_IDENTIFIER, ROOT_IDENTIFIER,
-            connectionIdentifiers, Collections.EMPTY_LIST
+            connectionIdentifiers, Collections.<String>emptyList()
         );
 
         // Build new user from credentials