You can change value 20 before starting animation
Output
Variable Name     Value in Memory
radius
no value
area
no value
  1  public class ComputeArea {
  2    public static void main(String[] args) {
  3      double radius; // Declare radius
  4      double area; // Declare area
  5  
  6      // Assign a radius
  7      radius = ; // New value is radius
  8  
  9      // Compute area
 10      area = radius * radius * 3.14159;
 11  
 12      // Display results
 13      System.out.println("The area for the circle of radius " +
 14        radius + " is " + area);
 15    }
 16  }