Provide Two Method Implementations for the following class: import java.util.Map

Question

Provide Two Method Implementations for the following class:

import java.util.Map;

import java.util.Set;

import java.util.List;

public class Graph {

public Graph() {

adjacency = new java.util.HashMap <>();

}

public void addEdge(T start , T end)

{

}

public boolean testPath(List vertexList)

{

}

private Map > adjacency;

}

Below is a sample tester method:

public static void main(String [] args)

{

Graph g = new Graph <>();

g.addEdge("A", "C");

g.addEdge("B", "C");

g.addEdge("A", "B");

System.out.println("Test results: " +

g.testPath(Arrays.asList("A", "B", "C")));

System.out.println("Test results: " +

g.testPath(Arrays.asList("B", "C", "A")));

g.addEdge("C", "A");

System.out.println("Test results: " +

g.testPath(Arrays.asList("B", "C", "A")));

try

{

g.testPath(Arrays.asList("Z"));

}

catch (Exception e)

{

System.out.println("Graph threw an exception (I expected that!)");

e.printStackTrace ();

}

}

Expected Output:

Test results: true

Test results: false

Test results: true

Graph threw an exception (I expected that!)

java.lang.RuntimeException: vertex list must contain at least two vertices

at Graph.testPath(Graph.java:30)

at Graph.main(Graph.java:77)

Explanation / Answer

import java.util.Map;

import java.util.Set;

import java.util.Arrays;

import java.util.HashSet;

import java.util.List;

public class Graph<T> {

public Graph() {

adjacency = new java.util.HashMap<>();

}

public void addEdge(T start, T end) {

Set<T> set = new HashSet<T>();

if (adjacency.get(start) != null) {

set = adjacency.get(start);

set.add(end);

adjacency.put(start, set);

} else {

set.add(end);

adjacency.put(start, set);

}

}

public boolean testPath(List<T> vertexList) throws Exception {

if(vertexList==null || vertexList.size()<=1)

throw new RuntimeException("vertex list must contain at least two vertices");

for (int i = 0; i < vertexList.size() - 1; i = i + 1) {

Set<T> set = adjacency.get(vertexList.get(i));

if (set == null)

return false;

if (i + 1 < vertexList.size() && !set.contains(vertexList.get(i + 1)))

return false;

}

return true;

}

private Map<T, Set<T>> adjacency;

//You can remove the below Lines, But make sure main throws exception
public static void main(String[] args) throws Exception {

//Remove the below closing brace as well
}

}

==========================================
One small change You need to make in the MAIN that You have

NOTE : Add the Line" throws Exception"

public static void main(String[] args) throws Exception {


Thanks, rest all will remain same. Let me know if there is any concern.

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