Thanks Ken - Not sure how I missed this one!

src/FlightRoutesGraph.java

@@ -0,0 +1,109 @@
+import edu.greenriver.sdev333.BSTSet;
+import edu.greenriver.sdev333.MathSet;
+import edu.greenriver.sdev333.HashSet;
+
+/**
+ * Created in class 3/13/23, Ken coding
+ *
+ * printlns added by me
+ *
+ * Importing interface MathSet - can we use this for testing?
+ */
+public class FlightRoutesGraph {
+
+    // two sets needed to model the graph
+    // 1. a set of vertices (points, nodes) - airports
+    // 2. a set of edges (connections, lines, relationships) - routes between airports
+
+    private class Edge {
+        private String node1;
+        private String node2;
+
+        public Edge(String from, String to) {
+            node1 = from;
+            node2 = to;
+        }
+    }
+
+    private MathSet<String> nodes;          // set of nodes
+
+    private MathSet<Edge> edges;            // set of edges
+
+    //Commented out so Main class would compile
+    public FlightRoutesGraph() {
+        nodes = new BSTSet<>();
+        edges = new HashSet<>();     // must use HashSet here as edges are not comparable
+    }
+
+    public void addNode(String city) {
+        nodes.add(city);
+    }
+
+    public void addEdge(String city1, String city2) {
+        Edge connection = new Edge(city1, city2);
+        edges.add(connection);
+    }
+
+    /*
+    Edge Set = {
+       ORD, JFK
+       JFK, MCO
+       DEN, PHX
+       LAS, DEN
+       DFW, ORD
+       ATL, JFK
+    }
+
+    IF we are looking for cities connected to Denver, we are looking for 'Adjacency, i.e. neighbors.
+     */
+
+    /**
+     * Return cities that are neigbors to given city.  There can be more than
+     * one neighbor, so should return a Set, i.e. MathSet of Strings/neighbors
+     *
+     * @param city
+     */
+    public MathSet<String> getNeighbors(String city) {
+        // create an empty  set to hold the results
+        MathSet<String> neighbors = new BSTSet<>();
+
+        // loop through edges and check if city is
+        // in either node1 or node2
+        for (Edge e: edges.keys()) {
+            if (e.node1.equals(city)) {
+                neighbors.add(e.node2);
+            }
+            else if (e.node2.equals(city)) {
+                neighbors.add(e.node1);
+            }
+        }
+
+        return neighbors;
+    }
+
+    public static void main(String[] args) {
+        FlightRoutesGraph g = new FlightRoutesGraph();
+
+        // add all the cities first (nodes)
+        g.addNode("JFK");
+        g.addNode("ORD");
+        g.addNode("ATL");
+        g.addNode("MCO");
+        g.addNode("DEN");
+
+        // add connections beween cities
+        g.addEdge("ATL", "MCO");
+        g.addEdge("JFK", "MCO");
+        g.addEdge("DEN", "ORD");
+        g.addEdge("ORD", "ATL");
+        // more to go if you want
+
+        // look for direct flights from JFK
+        MathSet<String> directFromJFK = g.getNeighbors("JFK");
+        MathSet<String> directFromATL = g.getNeighbors("ATL");
+
+        System.out.println(directFromJFK);
+        System.out.println(directFromATL);
+
+    }
+}

src/Main.java

@@ -1,5 +1,61 @@
+import edu.greenriver.sdev333.BSTSet;
+import edu.greenriver.sdev333.MathSet;
+import edu.greenriver.sdev333.HashSet;
+
+/**
+ * Used to test our set implementations.  Each class is declared twice to
+ * test against itself.  Uncomment/comment the appropriate lines to test
+ * a specific class (BSTSet or SeparateChainingHashSet)
+ *
+ * @author Paul Woods
+ */
 public class Main {
     public static void main(String[] args) {
-        System.out.println("Hello world!");
+
+        // Test BSTSet structures
+        MathSet<String> test1 = new BSTSet<>();
+        MathSet<String> test2 = new BSTSet<>();
+
+        // Test SeparateChainingHashTable structures
+        //MathSet<String> test1 = new HashSet<>();
+        //MathSet<String> test2 = new HashSet<>();
+
+        System.out.println("isEmpty() - should be true: " + test1.isEmpty());
+        System.out.println("size() - should be 0: " + test1.size());
+
+        System.out.println("adding 6 keys to set ... ");
+
+        test1.add("g");
+        test1.add("q");
+        test1.add("r");
+        test1.add("b");
+        test1.add("k");
+        test1.add("c");
+
+        System.out.println("size() - should be 6: " + test1.size());
+        System.out.println("isEmpty() - should be false: " + test1.isEmpty());
+        System.out.println();
+        System.out.println("contains('r') - should be true:  " + test1.contains("r"));
+        System.out.println("contains('a') - should be false:  " + test1.contains("a"));
+        System.out.println("contains('c') - should be true:  " + test1.contains("c"));
+        System.out.println("contains('z') - should be false:  " + test1.contains("z"));
+        System.out.println();
+
+        System.out.println("Creating 2nd set to test MathSet interface functions");
+
+        test2.add("z");
+        test2.add("a");
+        test2.add("b"); // in test1
+        test2.add("q"); // in test1
+        test2.add("j");
+        test2.add("c"); // in  test1
+
+        System.out.println("contents of test1: " + test1.toString());
+        System.out.println("contents of test2: " + test2.toString());
+        System.out.println();
+        System.out.println("test1.union(test2): " + test1.union(test2));
+        System.out.println("test1.intersection(test2): " + test1.intersection(test2));
+        System.out.println("test1.difference(test2): " + test1.difference(test2));
+
     }
 }