Question

(JAVA): The Collection ADT

1. We have a Circle class that includes radius attribute of type int, set by the constructor. Write a compareTo method for this class so that circle objects are ordered on the basis of their circumference (? = 2??).

2. We have a Person class that includes name and age attributes of type String and int respectively, both set by the constructor. Write a compareTo method for this class so that person objects are ordered on the basis of their name.

Answer 1

public class Circle implements Comparable<Circle> {
   private int radius;

   /**
   * @param aRadius
   */
   public Circle(int aRadius) {
       super();
       radius = aRadius;
   }

   /**
   * @return the radius
   */
   public int getRadius() {
       return radius;
   }

   /**
   * @param aRadius the radius to set
   */
   public void setRadius(int aRadius) {
       radius = aRadius;
   }

   @Override
   public int compareTo(Circle c) {
       //comparing the circumference of the both the objects
       return new Double(getCircumference()).compareTo(c.getCircumference());
   }
   //returns the circumference of the circle using 2 PI R formula
   public double getCircumference() {
       return 2 * Math.PI * radius;
   }

}

Answer 2:

public class Person implements Comparable<Person>{
   private String name;
   private int age;
   public Person(String aName, int aAge) {
       super();
       name = aName;
       age = aAge;
   }
   /**
   * @return the name
   */
   public String getName() {
       return name;
   }
   /**
   * @return the age
   */
   public int getAge() {
       return age;
   }
   /**
   * @param aName the name to set
   */
   public void setName(String aName) {
       name = aName;
   }
   /**
   * @param aAge the age to set
   */
   public void setAge(int aAge) {
       age = aAge;
   }
   @Override
   public int compareTo(Person p) {
       //comparing using the name so that Person objects will ordered based on name
       return getName().compareTo(p.getName());
   }
  
}
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