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public class Rectangle {
    private double width;
    private double height;
    
    /** create a Rectangle with given height and width */
    public Rectangle(double width, double height) {
         /* width is a member variable name, 
           to avoid confusion, we use this */        
        this.width = width;
        this.height = height;
    }
    
    /** create a sqare with the given width */
    public Rectangle(double width) {
        /* this is another usage of this:
           we use it to call another constructor 
           it is same as 
           this.width = width; 
           this.height = width */       
           this(width, width);
    }
    
    /** find out the perimeter of the rectangle */
    public double perimeter() {
        /* you can access the member variables */
        return 2*(height + width);
    }
    
    /** find out the area of the rectangle */
    public double area() {
        return height*width;
    }
    
    /** return the ratio of the area to the perimeter */
    public double areaToPerimeterRatio() {
        /* you can access the methods */
        return area()/perimeter();
    }
    
    /** multiply the rectange by x times */
    public void multiply(int x) {
         /* you can change the members width, height */
         width*=x;
         height*=x;
    }
    
    /** the function returns true if it can be contained in anther Rectangle */
    public boolean containedIn(Rectangle rect) {
        /* you can access the members of other rectangle */
        return height <= rect.height && width <= rect.width;
    }
    
    /** return the string representation of the class */
    public String toString() {
        /* toString method is used by System.out.println method 
          to print out the object. */ 
        return "height : " + height + ", " + "width: " + width;
    }
}

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public class RectangleTest {
    public static void main(String[] args) {
        Rectangle rect = new Rectangle(3,7);
        System.out.println(rect);
        System.out.println("Area: " + rect.area());
        System.out.println("Perimeter: " + rect.perimeter());
        System.out.println("Ratio: " + rect.areaToPerimeterRatio());
        System.out.println();
        System.out.println(rect.containedIn(new Rectangle(5,10)));
        System.out.println(rect.containedIn(new Rectangle(2,15)));
        System.out.println();
        rect.multiply(3);
        System.out.println("Multply by 3");
        System.out.println(rect);
    }
}

height : 7.0, width: 3.0
Area: 21.0
Perimeter: 20.0
Ratio: 1.05

true
false

Multply by 3
height : 21.0, width: 9.0