Java C3. oop basic pdf

1 Chapter 3. OOP Basic ITSS Java Programming CAO Tuan-Dung, HUT 2 Object - Oriented  Real world concepts can be modeled in a computer program  The program is made of objects with certain properties and operations that the objects can perform  It is not important how an object is implemented, but what it does  Every object is responsible for carrying out a set of related tasks 3 Object Oriented Real world Attribute Account name: Duc Binh Balance: 2.000.000 VND Deposit Debit Balance inquiry Operation request Balance inquiry I want to inquiry the balance Computer world Attribute name: Duc Binh Balance: 2.000.000 VND Deposit() Withdraw() checkBalance() operation operation Account object User object Message transmission checkBalance() 4 Class and Object  A group of objects with similar properties and behaviors is described by a class.  Class is a blueprint for an object.  A class contains fields and methods that define the behavior of the object.  A class is a description of a kind of object. 5 Class and Objects Attribute name: Duc Binh Balance: 2.000.000 VND Deposit() Withdraw() checkBalance() operation Account object of Mr Duc Binh Attribute name: Thu Lan Balance: 1.000.000 VND Deposit() Withdraw() checkBalance() operation Account object of Mrs Thu Lan Account Class (model of objects) Attribute Definition of member variable String name; long balance; void deposit(int money); void withdraw() int checkBalance() Method definition operation INSTANTIATE 6 Classes  A class can contain data declarations and method declarations int size, weight; char category; Data declarations Method declarations 7 class definition  Syntax: <modifier> class <name> { <Definition of member variable> <Definition of method> }  Example public class StudentRecord { // Definition of member variable // method definition } public class Account { // Definition of member variable // method definition } 8 Definition of member variable  Format: [Modifier] Data type Member variable name,…;  Example: public class Account { String name; // Account name long balance; // Balance : : void deposint (long money){ balance +=money; } } member variable can be used from anywhere if in the class 9 Method definition  Syntax: [Modifier] Return Value type method- name (Arguments list) { Body of method }  Example: public class Account { String name; // Account name long balance; // Balance : : void deposint (long money){ balance +=money; } } member variable can be used from anywhere if in the class 10 Variable length Argument  In the method, a variable-length argument that can pass many values can be declared. You may not pass the value to a variable-length argument.  In the method that uses a variable-length argument, we treat the passed argument as an array.  Syntax: [Modifier] Type of return value Method name (Data type name… Variable name) { Processing; } [...]... { name = pName; balance = pMoney; System.out.println(“It has 2 arguments "); System.out.print("Account name ： " + name); System.out.println(“/tBalance ： " + balance + "Yen"); } } 20 Solution: Overload .java class Overload { public static void main(String args[]) { Account obj = new Account(); obj.setData("Lan Anh", 100000); // Call display() method without argument obj.display(); // Call display() method... Account(); obj.display(); System.out.println(); // Generation of account object(Constructor with 2 arguments) Account obj2 = new Account(“Nam Hai", 100000); obj2.display(); } } 29 Assignment of variable  Basic data type int x = 20; int y = x;  Reference type x 20 y 20 Account obj = new Account(); Account act = obj Account Object obj act obj and act refer the same object 30 The static Modifier  We declare . 1 Chapter 3. OOP Basic ITSS Java Programming CAO Tuan-Dung, HUT 2 Object - Oriented  Real world concepts can be modeled