Object
public class CreateObjectDemo {
public static void main(String[] args) {
// Declare and create a point object and two rectangle objects.
Point originOne = new Point(23, 94);
Rectangle rectOne = new Rectangle(originOne, 100, 200);
Rectangle rectTwo = new Rectangle(50, 100);
// display rectOne's width, height, and area
System.out.println("Width of rectOne: " + rectOne.width);
System.out.println("Height of rectOne: " + rectOne.height);
System.out.println("Area of rectOne: " + rectOne.getArea());
// set rectTwo's position
rectTwo.origin = originOne;
// display rectTwo's position
System.out.println("X Position of rectTwo: " + rectTwo.origin.x);
System.out.println("Y Position of rectTwo: " + rectTwo.origin.y);
// move rectTwo and display its new position
rectTwo.move(40, 72);
System.out.println("X Position of rectTwo: " + rectTwo.origin.x);
System.out.println("Y Position of rectTwo: " + rectTwo.origin.y);
}
}
In computer science, an object can be a variable, a data structure, a function, or a method, and as such, is a value in memory referenced by an identifier.
A typical Java program creates many objects, which as you know, interact by invoking methods. Through these object interactions, a program can carry out various tasks, such as implementing a GUI, running an animation, or sending and receiving information over a network. Once an object has completed the work for which it was created, its resources are recycled for use by other objects.
Creating Objects
Point originOne = new Point(23, 94);
Rectangle rectOne = new Rectangle(originOne, 100, 200);
Rectangle rectTwo = new Rectangle(50, 100);
A class provides the blueprint for objects; you create an object from a class.
Each statement for creating objects has three parts: declaration (the code set in bold are all variable declarations that associate a variable name with an object type), instantiation (the new keyword is a Java operator that creates the object), initialization (the new operator is followed by a call to a constructor, which initializes the new object).
Related concepts
- The Type Comparison Operator instanceof
- Exceptions
- Exception handler
- Instance Variables
- Statements
- Object: Creating Objects
- Class: Instantiating a Class
- Class: Using the this Keyword
- Static Nested Classes
- Inner Classes
- Object as a Superclass
- The try-with-resources Statement
- The throw Statement
- Exceptions: How to Throw Exceptions
- Synchronized Methods
- Collections Framework
- The Collection Interface
- Iterator
- The List Interface
- The Map Interface