Question

Represent the control-flow graph as a set of nodes and a map between nodes and their neighbors. The following code snippet declares two classes—ControlFlowGraph and its static inner class Node—to enable the desired representation:

a. Implement the addNode method and the two addEdge methods.
b. Implement the reachable method.

Note: "..." is where code is to be inserted below the post condition

import java.util.*;

public class ControlFlowGraph {
// invariant : set " nodes " contains all nodes in the graph , i . e . , if
// there is an edge "m - > n " , both " m " and " n " are in " nodes "
   Set nodes; // set of nodes
   Map> edges; // adjacency set

   static class Node {
       String clazz; // containing class
       String method; // containing method
       int id; // unique identifier

       public Node(String clazz, String method, int id) {
           this.clazz = clazz;
           this.method = method;
           this.id = id;
       }

       public String toString() {
           return clazz + "." + method + ": " + id;
       }

       @Override
       public boolean equals(Object o) {
       // postcondition : returns true iff all attributes match ( up to " equals ")
           if(this == o) return true;
           if(o == null) return false;
          
           Node temp = (Node) o;
           if((!Objects.equals(this.clazz, temp.clazz)) ||
                   (!Objects.equals(this.method, temp.method)) ||
                       (this.id != temp.id))
               return false;
           else
               return true;
       }

       @Override
       public int hashCode() {
       // postcondition : satisfies the hash - code contract
           int hashKey = 31;
           int hash = 1;
           hash = hashKey * hash + ((this.clazz == null) ? 0 : clazz.hashCode());
           hash = hashKey * hash + ((this.method == null) ? 0 : method.hashCode());
           hash = hashKey * hash + this.id;
           return hash;
       }
   }

   public String toString() { // for ControlFlowGraph
       return "# nodes = " + nodes.size() + "\n nodes = " + nodes + "\n edges = " + edges;
   }

   public ControlFlowGraph() {
       nodes = new HashSet();
       edges = new HashMap>();
   }

   public void addNode(String clazz, String method, int id) {
   // postcondition : adds Node ( clazz, method, id ) to the set of nodes ,
   // and if the node is not previously in the set,
   // updates the adjacency - set representation to map the given node to an empty set
       Node toAddNode = new Node(clazz, method, id);
       if(nodes.contains(toAddNode))
           return;
      
       nodes.add(toAddNode);
       Set toAddSet = new HashSet();
       edges.put(toAddNode, toAddSet);
   }

   public void addEdge(String clazz1, String method1, int id1,
           String clazz2, String method2, int id2) {
   // postcondition : adds edge Node ( clazz1 , method1 , id1 ) -> Node ( clazz2 , method2 , id2 )
   // if any of the two nodes is not already in the set of nodes ,
   // the set is updated to include them
//... QUESTION A
   }

   public void addEdge(String clazz, String method, int id1, int id2) {
   // postcondition : adds edge between nodes identified by " id1 " and " id2 " ,
   // which are in the same method " method " in class " clazz "
   //... QUESTION A
   }

   public boolean reachable(String c1, String m1, int id1, String c2, String m2, int id2) {
       return false;
   // postcondition : returns true iff there is a directed path ( of length >= 0)
   // from Node ( c1 , m1 , id1 ) to Node ( c2 , m2 , id2 ) in the graph
// ... QUESTION B
   }

Answer 1

1 A

if(Node(clazz1) && Node(clazz2))

{

nodes.add(clazz1(edges),clazz2(edges))

}

else

{

Nodes.put(Nodes(clazz1),Nodes(clazz2))

}

2A

if(clazz1(method) ==clazz2(method)

{

edges.add(Node(id1),Node(id2))

}

1B

for(int i=0;i<c1;i++)

{

for(int j=0;j<c2;j++)

{

Edge.length = Node(i).id1+Node(j).id2;

}

}

if(Edge.length>0)

return true;

else

return false;