Question

Write a generic class Pair which has two type parameters—F and S—each representing the type of the first and second element of the pair, respectively. Add set and get methods for the first and second elements of the pair. (Hint: The class header should be public class Pair.)

Write a separate PairTest class to test class Pair. Create 2 Pair types and test your get and set methods on the following pair types:

• Pair

  p1 takes Integer and String types as a pair

• Pair

  p2 takes String and Integer

PairTest should output enough information to the terminal to show that your generic class Pair is able to set() and get() different types.

Answer 1

Pair.java

public class Pair {
  
   private F first;
   private S second;
   /**
   * @return the first element
   */
   public F getFirst() {
       return first;
   }
   /**
   * @param first the element first to set
   */
   public void setFirst(F first) {
       this.first = first;
   }
   /**
   * @return the second element
   */
   public S getSecond() {
       return second;
   }
   /**
   * @param second the element second to set
   */
   public void setSecond(S second) {
       this.second = second;
   }
}

PairTest.java

public class PairTest {

   /**
   * @param args
   */
   public static void main(String[] args) {
       /*Instance of Generic class Pair with parameters F-String and S-Integer*/
       Pair p1 = new Pair<>();
       p1.setFirst("Java");
       p1.setSecond(10);
      
       System.out.printf("The elements for First Pair are %s and %d.\n", p1.getFirst(),p1.getSecond());
      
       /*Instance of Generic class Pair with parameters F-Integer and S-String*/
       Pair p2 = new Pair<>();
       p2.setFirst(20);
       p2.setSecond("Python");

       System.out.printf("The elements for Second Pair are %d and %s.", p2.getFirst(),p2.getSecond());
   }

}

Output