you may also need to know how to iterate through all the items in data structurevisiting each one in turn so as to display it or perform some other action on it another important algorithm category is sorting there are many ways to sort dataand we devote "simple sorting,and "advanced sorting,to these algorithms the concept of recursion is important in designing certain algorithms recursion involves method calling itself we'll look at recursion in "recursion (the term method is used in java in other languagesit is called functionprocedureor subroutine some definitions let' look at few of the terms that we'll be using throughout this book database we'll use the term database to refer to all the data that will be dealt with in particular situation we'll assume that each item in database has similar format as an exampleif you create an address book using index cardsthese cards constitute database the term file is sometimes used in this sense record records are the units into which database is divided they provide format for storing information in the index card analogyeach card represents record record includes all the information about some entityin situation in which there are many such entities record might correspond to person in personnel filea car part in an auto supply inventoryor recipe in cookbook file field record is usually divided into several fields field holds particular kind of data on an index card for an address booka person' nameaddressor telephone number is an individual field more sophisticated database programs use records with more fields figure shows such recordwhere each line represents distinct field in java (and other object-oriented languages)records are usually represented by objects of an appropriate class individual variables within an object represent data fields fields within class object are called fields in java (but members in some other languages such as ++