If you have a class called, for example, Rectangle, you can add a method to it with the same name as the class. This method must have no return type, not even void. It is called a constructor. Here is an example:
Java > cat Rectangle.java
class Rectangle
{
double width;
double height;
Rectangle()
{
width = 2;
height = 3;
}
}
Java > javac Rectangle.java
Java >
The
purpose of a constructor is to give default values to a class member
when it is created. You can see what I mean below, where an instance of Rectangle is created. It automatically has a width of 2 and a height of 3:
Java > cat RectangleExample.java
public class RectangleExample
{
public static void main(String args[])
{
Rectangle r1 = new Rectangle();
System.out.println("width = " + r1.width);
System.out.println("height = " + r1.height);
}
}
Java > javac RectangleExample.java
Java > java RectangleExample
width = 2.0
height = 3.0
Java >
