| Types java app |
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| Data Types and Operators |
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| (Primitive Data Types) |
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| (Non-Primitive Data Types) |
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| Control Flow Statements |
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| Conditional Statements |
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| Looping Statements |
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| Branching Statements |
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| Object-Oriented Programming (OOP) |
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| Classes and Objects |
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| Inheritance |
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| Polymorphism |
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| Encapsulation |
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| Abstraction |
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| Exception Handling |
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| Introduction to Exceptions |
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| Collections Framework |
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| Overview of Collections |
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| Commonly Used Collections |
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| Iterators |
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| Java I/O |
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| File Handling |
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| Serialization |
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| Multithreading |
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| Introduction to Threads |
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| Thread Synchronization |
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| GUI Programming with Swing |
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| Introduction to Swing |
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| Event Handling |
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| Advanced Topics |
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| Java Database Connectivity (JDBC) |
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| JAVA CODE |
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Java Basics
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Working with Objects
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Arrays, Conditionals, and Loops
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Creating Classes and Applications in Java
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More About Methods
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Java Applet Basics
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Graphics, Fonts, and Color
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Simple Animation and Threads
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More Animation, Images, and Sound
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Managing Simple Events and Interactivity
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Creating User Interfaces with the awt
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Windows, Networking, and Other Tidbits
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Modifiers, Access Control, and Class Design
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Packages and Interfaces
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Exceptions
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Multithreading
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Streams and I/O
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Using Native Methods and Libraries
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Under the Hood
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Java Programming Tools
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Working with Data Structures in Java
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Advanced Animation and Media
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Fun with Image Filters
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Client/Server Networking in Java
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Emerging Technologies
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appendix A :- Language Summary
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appendix B :- Class Hierarchy Diagrams
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appendix C The Java Class Library
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appendix D Bytecodes Reference
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appendix E java.applet Package Reference
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appendix F java.awt Package Reference
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appendix G java.awt.image Package Reference
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appendix H java.awt.peer Package Reference
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appendix I java.io Package Reference
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appendix J java.lang Package Reference
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appendix K java.net Package Reference
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appendix L java.util Package Reference
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Creating objects in Java involves understanding several key concepts: classes, objects, constructors, and the
new keyword. Let’s break these down step by step.1. Classes
A class is a blueprint for objects. It defines a type and contains fields (variables) and methods to define the behavior of objects created from the class.
public class Car {
// Fields
String color;
String model;
int year;
// Constructor
public Car(String color, String model, int year) {
this.color = color;
this.model = model;
this.year = year;
}
// Methods
public void displayDetails() {
System.out.println("Car model: " + model);
System.out.println("Car color: " + color);
System.out.println("Car year: " + year);
}
}
2. Creating Objects
To create an object of a class, you need to use the
new keyword followed by the class constructor.
public class Main {
public static void main(String[] args) {
// Creating an object of the Car class
Car myCar = new Car("Red", "Toyota", 2021);
// Accessing methods
myCar.displayDetails();
}
}
Detailed Steps:
- Define the Class: Create a class with fields and methods. Optionally, include a constructor to initialize objects.
- Create an Object: Use the
newkeyword followed by the class constructor to create an object. - Access Members: Use the dot
.operator to access fields and methods of the object.
Constructors
A constructor is a special method that is called when an object is instantiated. It initializes the object.
- Default Constructor: If no constructor is defined, Java provides a default constructor.
- Parameterized Constructor: A constructor with parameters to initialize fields.
public class Car {
String color;
String model;
int year;
// Default Constructor
public Car() {
this.color = "Unknown";
this.model = "Unknown";
this.year = 0;
}
// Parameterized Constructor
public Car(String color, String model, int year) {
this.color = color;
this.model = model;
this.year = year;
}
}
Instantiating Objects with Constructors
- Using the default constructor:
Car myDefaultCar = new Car();
myDefaultCar.displayDetails();
- Using the parameterized constructor:
Car myParamCar = new Car("Blue", "Honda", 2022);
myParamCar.displayDetails();
Access Modifiers
Access modifiers control the visibility of class members.
public: Accessible from any other class.private: Accessible only within the defined class.protected: Accessible within the same package and subclasses.default(no modifier): Accessible only within the same package.
public class Car {
private String color;
private String model;
private int year;
// Getter and Setter for color
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
// Other methods and constructors...
}
Example Program
Here’s a full example putting everything together:
public class Car {
private String color;
private String model;
private int year;
// Default Constructor
public Car() {
this.color = "Unknown";
this.model = "Unknown";
this.year = 0;
}
// Parameterized Constructor
public Car(String color, String model, int year) {
this.color = color;
this.model = model;
this.year = year;
}
// Getter and Setter methods
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public String getModel() {
return model;
}
public void setModel(String model) {
this.model = model;
}
public int getYear() {
return year;
}
public void setYear(int year) {
this.year = year;
}
// Method to display details
public void displayDetails() {
System.out.println("Car model: " + model);
System.out.println("Car color: " + color);
System.out.println("Car year: " + year);
}
}
public class Main {
public static void main(String[] args) {
// Creating an object using the default constructor
Car defaultCar = new Car();
defaultCar.displayDetails();
// Creating an object using the parameterized constructor
Car paramCar = new Car("Red", "Toyota", 2021);
paramCar.displayDetails();
// Using getter and setter methods
paramCar.setColor("Blue");
System.out.println("Updated color: " + paramCar.getColor());
}
}
This example demonstrates the fundamental principles of creating and using objects in Java, including class definition, constructors, access modifiers, and methods.
