Programming Problem 18.12 hashCode and equals methods for the Pair class with LabRat

Provide suitable hashCode and equals methods for the Pair class of Section 17.2 and implement a HashMap class, using a HashSet>.

Complete the following classes in your solution:

public class Pair { private T first; private S second; public Pair(T firstElement, S secondElement) { first = firstElement; second = secondElement; } public T getFirst() { return first; } public S getSecond() { return second; } public boolean equals(Object otherObject) { . . . } public int hashCode() { . . . } } 

import java.util.HashSet; import java.util.Collection; import java.util.Set; public class HashMap { private HashSet> set; public HashMap() { . . . } public void put(K key, V value) { . . . } public V get(K key) { . . . } public V remove(K key) { . . . } public Set keySet() { . . . } public int size() { return set.size(); } }

Use the following class as your tester class:

import java.awt.Color; import java.util.Map; import java.util.Set; /** This program tests a map that maps names to colors. */ public class MapTester { public static void main(String[] args) { HashMap favoriteColors = new HashMap(); favoriteColors.put("Juliet", Color.PINK); favoriteColors.put("Romeo", Color.GREEN); favoriteColors.put("Adam", Color.BLUE); favoriteColors.put("Eve", Color.PINK); favoriteColors.put("Romeo", Color.WHITE); favoriteColors.remove("Juliet"); System.out.println(favoriteColors.get("Romeo")); System.out.println("Expected: java.awt.Color[r=255,g=255,b=255]"); System.out.println(favoriteColors.get("Juliet")); System.out.println("Expected: null"); System.out.println(favoriteColors.size()); System.out.println("Expected: 3"); Set keys = favoriteColors.keySet(); System.out.println(keys.size()); System.out.println("Expected: 3"); } }