Chapter2 bag2
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This document provides an introduction to object-oriented programming concepts including the differences between procedural and OOP languages, basic Java terminology like classes, objects, attributes, methods, and encapsulation. It discusses what objects are, how to identify, define, create and operate on objects. It also covers object relationships like association, inheritance and mutability. Finally, it discusses modeling languages/symbols like UML, class definition, creating objects, object methods, and the Java System class.
Chapter2 bag2
- 1. 2.1 Introduction to Object- Oriented Programming
- 2. 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
- 3. 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
- 4. 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
- 5. 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
- 6. 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
- 7. 2.2.7 Encapsulation • To hide the details, package together • Access modifiers – public, private and protected
- 8. 2.2.8 Object relationships • Association – Objects know about each other • Whole-part – Existance of an object relies on another • Inheritance – Attributes & behaviors can be inherited
- 10. 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
- 11. 2.3.1 Modeling languages and symbols • Unified Modeling Language (UML) standardizes symbols & terminology for diagramming objects
- 12. 2.3.2 Basic Class symbol • Rectangle represents a class of objects • 3 compartments: Name, attributes , and operations or methods • Symbols indicate accessibility
- 13. 2.4.1 Class definition •Defined by using public class Person { private String name; the class keyword public Person(String theName) { •Public classes name = theName; defined in separate } } files •Filename must be the same as the class name
- 14. 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
- 15. 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
- 16. 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!”);