2.1 Introduction to Object-Oriented Programming

2.1.1 Procedural versus OOP languages Procedural programming involves creating a sequence of instructions OOP uses a collection of interacting objects Functions are logically grouped, making enhancements easy OOP can model human problem-solving

2.1.2 Basic Java terminology Object. contains data and instructions Class. blueprint for an object Attribute. describe the state of objects Data Type. describes what kind of information a certain attribute is Behavior. describe what objects can do Method. a set of instructions Inheritance. Some objects derive attributes and behaviors from other objects Encapsulation. Combining data and methods together

2.2 What are Objects? 2.2.1 Introduction to objects Anything tangible or abstract that is relevent Objects can have attributes and behaviors Attributes describe the object Behaviors describe what the object can do

2.2.2 Classification of objects User Interface objects Objects that the user interacts directly with Operating environment objects Provide services to other components Task Related objects Documents, multimedia, problem domain

2.2.3 Objects - identifying, defining, creating and operating on Identifying – Requires needs assessment Defining – Classification, relationships, operations. The class keyword Creating – The constructor and the new keyword Operating – Using an object’s methods

2.2.7 Encapsulation To hide the details, package together Access modifiers – public, private and protected

2.2.8 Object relationships Association Whole-part Inheritance Objects know about each other Whole-part Existance of an object relies on another Inheritance Attributes & behaviors can be inherited

2.2.9 Inheritance

2.2.10 Object mutability and destruction Some object attributes should be immutable, or unchangable To make an item immutable, use the final keyword The JVM automatically releases memory when objects are no longer required The garbage collector will reclaim memory by objects that are no longer referenced Garage collection is not controllable

2.3.1 Modeling languages and symbols Unified Modeling Language (UML) standardizes symbols & terminology for diagramming objects

2.3.2 Basic Class symbol Rectangle represents a class of objects 3 compartments: Name, attributes , and operations or methods Symbols indicate accessibility

2.4.1 Class definition Defined by using the class keyword Public classes defined in separate files Filename must be the same as the class name public class Person { private String name; public Person(String theName) { name = theName; }

2.4.2 Creating objects Constructor methods are called when an object is created All object data is stored in memory Variables are a reference to the memory location

2.4.3 Object methods Mutator – Changes object data Accessor – Retrieves object data Methods with no arguments Methods that require arguments Method return values – Provide a result to the caller

2.5.1 System class Data stored by an object is member data Data present in an object’s methods is called local or temporary data Java.lang.System is a pre-defined object that can be used to perform system tasks System.out.println(“Hello World!”);