Application: Program Elements: Program is a set of instructions.Every Program consists, Syntax Examples datatype identity = value; String name = “amar”; int age = 23; double salary = 35000.00; boolean married = false; Syntax Example returntype identity(arguments){ body;} int add(int a, int b){ int c = a+b; return c;}
Introduction to Object oriented programming: Note: We implement Object-Oriented functionality using Classes and Objects Class: Class contains variables and methods. Java application is a collection of classes Syntax Example class ClassName{ Variables ; & Methods ;} class Account{ long num; String name; double balance; void withdraw(){ logic; } void deposit(){ logic; }} …
Encapsulation: Inheritance: Abstraction: Polymorphism: Types of Relations between Classes/Objects in Java: There are three most common relationships among classes in Java that are as follows:
Class Members: Variables: Variable stores information of class(object).We store information in java using 4 types of variables Blocks: Static Block: Defining a block using static-keyword. JVM invokes static block when class execution starts. static{ statements;} Instance Block: Defining a block without static-keyword. JVM invokes instance block every time when object creates. { statements;} Methods: Static …
Static Members: Static main() method: public static void main(String[] args)Orpublic static void main(String args[]) Program to display Hello World on Console: public class Code{ public static void main(String[] args){ System.out.println(“Hello World”); }} Class without main(): We can define class without main() method but we cannot run that class. public class Code{ void fun(){ System.out.println(“fun…”); }} …
Static block: class Pro{ static{ System.out.println(“Static block”); } public static void main(String args[]){ System.out.println(“Main method”); }} Output: Static Block Main method
Method: Syntax Example returntype identity(arguments){ statements;} int add(int a, int b){ int c=a+b; return c;} Classification of Methods: Based on taking input and returning output, methods are classified into 4 types. Method Definition: Method definition consists logic to perform the task. It is a block. Method Call: Method Call is used to invoke the method …
Static Variable: class Bank{ static String bankName = “AXIS”;} Note: We always process the data (perform operations on variables) using methods. Getter and Setter Methods: class Code{ static int a; static void setA(int a){ Code.a = a; } static int getA(){ return Code.a; } public static void main(String[] args){ Code.setA(10); System.out.println(“A val : ” + …
Instance Members: Object Creation of a Class in java: Syntax: ClassName ref = new ClassName(); Example: Employee emp = new Employee(); Constructor: class Employee{ Employee() { System.out.println(“Constructor”); }} We must invoke the constructor in Object creation process: class Employee{ Employee() { System.out.println(“Object created”); } public static void main(String args[]) { Employee emp = new Employee(); …
Instance Method: No arguments and No return values method: class Code{ public static void main(String[] args) { Code obj = new Code(); obj.fun(); } void fun(){ System.out.println(“fun”); }} With arguments and No return values method: class Code{ static void main(String[] args) { Code obj = new Code(); obj.isEven(4); obj.isEven(13); } static void isEven(int n){ if(n%2==0) …