Java variables,
Array, 2d array
Method
Different method invoking and return type
Class
– Class is actually a blueprint/specification/design
– A class can create as many as objects it needs to create
Object
– Earth is a software application where human and other thing is software objects.For creating object we need to create a human class
– Objects do particular behavior in a class
– Object exist only in application runtime actually when application is running
– Objects have identity,state and behavior
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this keyword – it represent current object
Instance
Constructor – The costructor is a special method with the same name as the class and it’s used to instantiate objects from that class
– Every class has a by default constructor if we don’t put it manually
– The constructor is special method containing instructions for object creation. it can be said it is so called birth method. It has instructions for how the object will be born when the application starts up
Static keyword
Stack and heap memory
Garbage collection
Object oriented Programming = better organizing of code, it is a way to organize our code from multiple files by creating objects
Local variable
Reference variable
Instance variable
Inheritance
– Inheritance is the approach to get/transfer behaviour of one class to another
– We use extends keyword for inheriting, in inheritance we inherit from parent class which known as base class and the class which needs inheritation is known as child class or sub class/derived class
– super keyword it extract constructor and it’s variable from parent class but reverse is not possible
Overrides
– Same method name with different purpose
– Same method name in parent class but in child class the method name is same but with different purpose
– Overrides means replace
– Override is not a good idea sometimes so we go for interface
Interfaces
– Interface is a contract with a class. The class needs to implements that method of the interface according to contract
– Interface has a method which does not need body, so it is just only to define, it is called as abstract method
– one parent class
– We use implements keyword while putting interface in a class
Abstract class
– When you don’t need all methods to invoke you can use abstract method, you can not make object from abstract class. Abstract method needs to be in abstract class. We use abstract keyword for both method and object to define abstract class and methods
– you can only extend abstract class but can not instantiate abstract class
– We can define abstract class as a type while creating object
Polymorphism
Loops
Exception Handling
Collection Framework
Wrapper class
Threading
Concurrency
Database
Jshell
Functional Interfaces
Lambda expressions
-Lambda helps us to use separate from associated object
– it can run without class
– We need to use lot of interfaces for this
Streams
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Italic kora jaygagula motamuti clear asey In Sha Allah, Alhamdulillah
The source is : Imtiaz Ahmed’s complete Java course
OOP Design New Course:
Association: It defines relationship between classes, it defines how the software will behave
Dependency Association: For example from code:
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public class Driver { public void drive(Vehicle raceCar){ raceCar.accelerate(); } } |
A driver receives a vehicle reference only as driver then only he can drive or accelerate
Composition: A particular object . It imply ownership
for example in this code:
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package Lesson_1; public class Vehicle1 { Engine myEngine; //c public vehicle(Engine anEngine){ myEngine=anEngine; } public void operateVehicle(){ myEngine.start(); } } |
Aggregation Association: It does not imply ownership
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public class SchoolLanguageDepartment{ SpanishCourse spanish; FrenchCourse french; HindiCourse hindi; BanglaCourse bangla; } |
Here Department to SpanishCourse relation is composite
But Course to Student relationship is not composite because it does not imply ownership a student can take many courses or not
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public class HistoryCourse{ Student[] registeredStudent; } |
We find this relationship from above diagram, the block diamond and white diamond is the part of UML diagram
Forming Association between objects:
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public class NewsPaperCompany{ Customer customer; public void setCustomer(Customer aCustomer){ customer=aCustomer; } } |
has a relationship in customer .
Now when to stop delivery
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public class Customer{ NewsPaperCompany paperCompany; public void setNewsPaperCompany(NewsPaperCompany aPaperCompany) { paperCompany=aPaperCompany; } public void cancelSubscription{ paperCompany.stopDelivery(); } } |
Overview of software deisgn:
For example: Hospital Employee Management System
Task of the software:
Hire and Terminate Employees
Print Reports(XML,CSV Formats)
Problem Statement:
Current status of the software
Tips for design:
You must draw design in paper or whiteboard don’t go to code directly
Don’t overdesign or overdraw
We have to develop iteratively but early steps should be kept simple
Class names should be nouns based on their intention
Single Responsibility Priniciple(SRP): Not all the things in the same class
Don’t repeat yourself(DRY):
Arrow sign always describe that it is depends on that dependency class:
DAO=Data Access Object
Source Imtiaz Ahmed Master OOP Design course
