[Java] I don't get new area for my program

Question

public class Main
{

private int length;
private int width;
private int area;

public Main(int l,int w){
this.length=l;
this.width=w;
this.area=l*w;
}

public void setlength(int newl){
this.length=newl;
}
public int getlength(){
return this.length;
}
public void setwidth(int neww){
this.width=neww;
}
public int getwidth(){
return this.width;
}
public int getarea(){
return this.area;
}
public static void main(String[] args) {
Main test = new Main(1,2);
System.out.println(test.getarea()); //prints the area as 2
test.setlength(5); //tried to change the length of my rectangle object
System.out.println(test.getarea()); //Still prints the area as 2???????
}
}
I made the code above using just an online IDE. This computes the area of a rectangle.

When I updated the length of my rectangle object, the area still remains the same and I don't understand why???

Answer 1

Why would it change? Numbers are passed by value, so it doesn't change wgen you set the length.
You actually don't need an area variable, a function is enough:
public int getArea() {
return length * width;
}

Answer 2

you should recalculate the area in setlength

Answer 3

If you want to update the area attribute every time the length or width is updated, you can do it in your setters.

public void setlength(int newl){
length = newl;
area = length * width;
}

public void setwidth(int neww){
width = neww;
area = length * width;
}

This is, however, cumbersome and in no way better than what Airree has suggested, which is to modify your getArea() method to just return length * width.

Answer 4

So to confirm, the 'area' inside my constructor only stores the initial value when an object's length and width is initialised??

I was hoping that when I do use the 'setlength()' function, the 'area' variable inside my constructor updates......

I understand the solutions you guys have said for the function 'public int getArea()'

Guess I have to update the area under each setter function if there isn't any way to update the object's area within the constructor