adt in ( time thusa doubly linked list is an efficient implementation of the list adt node list implementation in java portions of the java class nodepositionlistwhich implements the node list adt using doubly linked listare shown in code fragments code fragment shows nodeposition list' instance variablesits constructorand methodcheckpositionwhich performs safety checks and "unwrapsa positioncasting it back to dnode code fragment shows additional accessor and update methods code fragment shows additional update methods code fragment portions of the nodepositionlist class implementing the node list adt with doubly linked list (continues in code fragments and