How to input a value for an integer variable

quoting: http://javaalmanac.com/egs/java.io/ReadFromStdIn.html

e34. Reading Text from Standard Input

    try {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String str = "";
        while (str != null) {
            System.out.print("> prompt ");
            str = in.readLine();
            process(str);
        }
    } catch (IOException e) {
    }

the method process(str) would be the place that you would do something like:

try {
len = Integer.parseInt(str) ;
} catch (Exception e) {
// bad input
}

Do I have to include or import any files to use the above code?

java.io.BufferedReader
java.io.InputStreamReader

This is my code. Where am I going wrong?

import java.io.BufferedReader;
import java.io.InputStreamReader;

class Rectangle {
private int length;
private int width;
public Rectangle(int l, int w) {
length = l;
width = w;
}
public int calculateArea() {
return length * width;
}
public int calculatePerimeter() {
return (2 * length + 2 * width);
}
public static void main(String args[]) {
    int l,w,area,perimeter;
    System.out.println("Input length:");
    try {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String str = "";
        while (str != null) {
            System.out.print("> prompt ");
            str = in.readLine();
            process(str);
        }
    } catch (IOException e) {
    }

    System.out.println("Input width:");
    Rectangle rect = new Rectangle(l,w);
        area = rect.calculateArea();
        perimeter = rect.calculatePerimeter();
        System.out.println("The area of the rectangle is: ");
       
System.out.println(area);
System.out.println("The perimeter of the rectangle is: ");
System.out.println(perimeter);

}
}

Thank you.