getting weird output

[budsy remo]

i wrote this code

import static java.lang.System.*;
class Q8
{	
	public static void main(String... args)
	{
		if(args.length==0)
		{
			out.println("you didn't enter anything");
		}
		else
		{	
			if(args.length==2)
			out.println(new Rectangle(Integer.valueOf(args[0]),Integer.valueOf(args[1])));
			else if(args.length==1)
			out.println(new Rectangle(Integer.valueOf(args[0])));	
		}
	}
}
class Rectangle
{
	public Rectangle(double side)
	{
		out.println("It's a Square");
		out.println(side*side);
	}
	public Rectangle(double length,double breadth)
	{
		out.println("It's a Rectangle");
		out.println(breadth*length);
	}
}

when i type
java Q8 12
i get

It's a Square
144.0
Rectangle@19821f

Why do i get "Rectangle@19821f" ?

[Henry Wong]

budsy remo wrote:
Why do i get "Rectangle@19821f" ?

When you print out the object, System.out.print() will call toString() on the object to get a string that it can print. And since, you didn't implement the toString() method, it will inherit it from the Object class. The toString() method of the Object class generates a string with the class type and the identity hash code, which is what you see.

Henry

[Tom Reilly]

As Mr. Wong said, you defined a class called Rectangle but did not override the toString() method so when you tried to print the Rectangle instance at line 15, it called the default toString() method as implemented in the Object class, which Rectangle extends. If you override the toString() method, you can display whatever you want.

In the code below, I modified your Rectangle class to implement a toString() method. Note the @Override annotation on line 35. This is not mandatory but tells the compiler the method that follows overrides a method of the base class. If you get the syntax of the method wrong, the compiler will tell you.

import static java.lang.System.*;

class Q8
{   
    public static void main(String... args)
    {
        if(args.length==0)
        {
            out.println("you didn't enter anything");
        }
        else
        {   
            if(args.length==2)
            out.println(new Rectangle(Integer.valueOf(args[0]),Integer.valueOf(args[1])));
            else if(args.length==1)
            out.println(new Rectangle(Integer.valueOf(args[0])));   
        }
    }
}
class Rectangle
{
    double side;
    public Rectangle(double side)
    {
        this.side = side;
        out.println("It's a Square");
        out.println(side*side);
    }
    public Rectangle(double length,double breadth)
    {
        out.println("It's a Rectangle");
        out.println(breadth*length);
    }
    
    @Override
    public String toString()
    {
        String sSide = Double.toString(this.side); 
        String msg = String.format("Rectangle.side = %s", sSide);
        return msg;
    }
}

[budsy remo]

Thanks a lot guys.