import java.util.Comparator; import java.util.Set; import java.util.TreeSet; /** A program to test a tree set with a comparator for coins. */ public class TreeSetTester { public static void main(String[] args) { Coin coin1 = new Coin(0.25, "quarter"); Coin coin2 = new Coin(0.25, "quarter"); Coin coin3 = new Coin(0.01, "penny"); Coin coin4 = new Coin(0.05, "nickel"); class CoinComparator implements Comparator { public int compare(Coin first, Coin second) { if (first.getValue() < second.getValue()) return -1; if (first.getValue() == second.getValue()) return 0; return 1; } } Comparator comp = new CoinComparator(); Set coins = new TreeSet(comp); coins.add(coin1); coins.add(coin2); coins.add(coin3); coins.add(coin4); for (Coin c : coins) System.out.print(c.getValue() + " "); System.out.println("Expected: 0.01 0.05 0.25"); } }