sets and maps returns none to indicate the key is not contained in the map when used by the other methodsthe value returned can be evaluated to determine both the existence of the key and the location of the corresponding entry if the key is in the map by combining the two searches into single operationwe eliminate the need to first determine if the map contains the key and then searching again for its location given the helper methodthe implementation of the various methods is straightforward implementation of the iterator method is left as an exercise multi-dimensional arrays in we worked with oneand two-dimensional arraysbut arrays can be larger than two dimensions in factarrays can contain any number of dimensions that may be needed for given problem multi-dimensional array stores collection of data in which the individual elements are accessed with multicomponent subscriptsxi, or yi, , figure illustrates the abstract view of twoand three-dimensional array as we saw earliera two-dimensional array is typically viewed as table or grid consisting of rows and columns an individual element is accessed by specifying two indicesone for the row and one for the column the three-dimensional array can be visualized as box of tables where each table is divided into rows and columns individual elements are accessed by specifying the index of the table followed by the row and column indices larger dimensions are used in the solutions for some problemsbut they are more difficult to visualize columns les tab rows rows columns figure sample multi-dimensional arrays(lefta - array viewed as rectangular table and (righta - array viewed as box of tables most high-level programming languages provide convenient way to create and manage multi-dimensional arrays while others require more hands-on approach +and java are two examples of languages that provide multi-dimensional arrays as part of the language pythonof coursedoes not directly support arrays of any dimension but that did not prevent us from defining and implementing abstract data types in the previous for oneand two-dimensional arrays likewisewe can define an abstract data type for creating and using arrays of any dimension