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Understanding Objects, Classes, and Methods in Object-Oriented Programming

Computer programming has evolved from top-down procedural methodologies to Object-Oriented Programming (OOP), where real-world entities are represented as Abstract Data Types (ADTs). In OOP, a class defines the structure and behavior of an object, encapsulating its properties and methods. For instance, a BankAccount class might include private instance fields like balance and password, along with public methods for creating accounts, depositing, withdrawing, and viewing balances. This encapsulation ensures data privacy and helps manage complexity in programming.

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Understanding Objects, Classes, and Methods in Object-Oriented Programming

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  1. Objects, Classes, & Methods (2.3) • Computer Programming is basically the manipulation of data. How programmers manipulate data has changed from a top-down procedural programming methodology into Object Oriented Programming. • In OOP, we define real world entities as user defined types called Abstract Data Types (ADT). • ADTs are the Objects in OOP representing Real World Entities. • Bank Accounts • Employee Records • Graphical Shapes • Etc… • A Classis the mechanism we use to define an Object (ADT) in Java. • A Class has the capability to encapsulate everything an Object needs to know about itself! • Objects can contain dataand the actions or behaviors to manipulate that data. • data -> Instance Fields • behavior ->Methods ( functions that manipulate data)

  2. Consider developing a BankAccountclass • Data (Instance Fields) -> might include – usually declared private: • balance -> myBalance • myPassword • myInterestRate • Behaviors (Methods) might include – usually declared public: • createAccount( ) • deposit( ) • withdraw( ) • viewBalance( ) • Every class has methods which can be called (invoked) by a class object (variable of a class). • Every Object belongs to a Class! • Class Variables - A class is usually stored as a separate file which is used in another program (Client Code). Class variables must be declared in-order for the Object to manipulate its data. BankAccount acct = new BankAccount( ); acct.deposit(depositAmount); • Manipulating an Objects data indirectly through public methods is referred to as Encapsulation or Data-Hiding. • We make an Objects data private to restrict direct outside access!

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