How do I validate a value passed by the Set?

I wanted to know how I would do when adding a new value for the length and width through setLength and SetWidth, and that value goes through validation ((x > 0 & x < 20)? x: 0 ):

public class Rectangle {

private double length;
private double width;

//Construtor

public Rectangle(){
    this(1.0,1.0);
}
public Rectangle(double l){
    this(l,1.0);
}
public Rectangle(double l, double w){
    setValues(l, w);
}

//Set and verify values

public void setValues(double l, double w){
    setLength(l);
    setWidth(w);
}

public void setLength(double l){
    length = ((l > 0 && l < 20) ? l : 0);
}
public void setWidth(double w){
    width = ((w > 0 && w < 20) ? w : 0);
}


//Get
public double getLength(){
    return length;
}
public double getWidth(){
    return width;
}

//Calc perimeter
public double calcPerimeter(double l, double w){
    return (l+w)*2;
}
//Calc area
public double calcArea(double l, double w){
    return (l*w);
}

}

In my test it passes directly through the IF in the set:

    import java.util.Scanner;

    public class RectangleTest {
    public static void main(String[] args) {


    //Teste do Construtor sobrecarregado
    Rectangle myRectangle1 = new Rectangle();
    Rectangle myRectangle2 = new Rectangle(2.0);
    Rectangle myRectangle3 = new Rectangle(2.0, 3.0);
    Rectangle myRectangle4 = new Rectangle(21.0, 3.0);


System.out.printf("Sem argumentos: %.1f\n", myRectangle1.getLength());
System.out.printf("Sem argumentos: %.1f \n\n", myRectangle1.getWidth());

System.out.printf("Com um argumento: %.1f \n", myRectangle2.getLength());
System.out.printf("Com um argumento: %.1f \n\n",   myRectangle2.getWidth());

System.out.printf("Com dois argumentos: %.1f \n", myRectangle3.getLength());
System.out.printf("Com dois argumentos: %.1f \n\n",myRectangle3.getWidth());

System.out.printf("Com número maior que 20: %.1f \n", 
myRectangle4.getLength());
System.out.printf("Com dois argumentos: %.1f \n\n",      
myRectangle4.getWidth());
    //Fim do teste de construtor sobrecarregado

    Rectangle myRectangle = new Rectangle(1.0 , 1.0); //Define valor inicial 
    como 1.0
    Scanner input = new Scanner(System.in);

    double length;
    double width;

    System.out.print("\nComprimento: "); //Solicita o valor de Length
    length = input.nextDouble();
    myRectangle.setLength(length);//Determina o novo valor de Length

    System.out.print("Largura: "); //Solicita o valor de Width
    width = input.nextDouble();
    myRectangle.setWidth(width); //Determina o novo valor de Width



    System.out.printf("Perímetro: %.1f \t", 
    myRectangle.calcPerimeter(length, width)); //Calcula o perímetro e exibe 

    System.out.printf("Área: %.1f \n\n", myRectangle.calcArea(length, 
    width)); //Calcula a área e exibe o resultado

    }
    }