Constructors__1_

Class Constructors

Definition

• Constructors are special methods called during the creation of an object.

• They share the same name as the class.

• Constructors do not have a return type, not even void.

Characteristics

• Multiple constructors can exist within a class; they must differ in parameters, which is known as having different signatures.

• If no constructor is defined, a default constructor is automatically created by the compiler.

Types of Constructors

• There can be only one parameterless default constructor.

• Constructors are invoked when an object is created using the new keyword.

• Primitive types are automatically initialized to default values upon creation.

Example in Code

public static void main(String[] args) {
    MyPoint p = new MyPoint();
    // Constructor is called
}

Using Constructors

Object Creation

• When creating objects from classes, the appropriate constructor along with itsparameters should be utilized.

• Example: A MyPoint constructor requires two parameters to be specified.

The Static Keyword

Definition and Access

• Static members defined in a class can be accessed without creating an object instance of that class.

• They occupy only one memory location and maintain just a single copy.

• Changes made to static members in one part of the code will affect all other uses of that member.

Declaration

• Static members are declared using the static keyword.

Static Methods

Example Class Definition

public class MyMath {
    public static double PI = 3.1416;
    public static double CalculateArea(double radius) {
        return PI * radius * radius;
    }
}

class Test {
    public static void main(String [] args) {
        double myradius = 4.3;
        System.out.println(MyMath.CalculateArea(myradius));
        // Function is called without using an object
    }
}

Application in a Game Context

• In a game scenario, modeling alien races like Martians:

  • Martians may attack if there are at least 3 Martians.

  • A strategy must be established to enable each Martian to know the number of Martians around.