所以我在java中有一个图的邻接矩阵实现。我正在尝试编写一个驱动程序来正确测试它。我开始使用像toString和addEdge这样的基本方法。 这是图表实现：
import java.util.*;
/**
* Graph represents an adjacency matrix implementation of a graph.
*
* @author Java Foundations
* @version 4.0
*/
public class Graph<T> implements GraphADT<T>
{
protected final int DEFAULT_CAPACITY = 5;
protected int numVertices; // number of vertices in the graph
protected boolean[][] adjMatrix; // adjacency matrix
protected T[] vertices; // values of vertices
protected int modCount;
/**
* Creates an empty graph.
*/
public Graph()
{
numVertices = 0;
this.adjMatrix = new boolean[DEFAULT_CAPACITY][DEFAULT_CAPACITY];
this.vertices = (T[])(new Object[DEFAULT_CAPACITY]);
}
/**
* Returns a string representation of the adjacency matrix.
*
* @return a string representation of the adjacency matrix
*/
public String toString()
{
if (numVertices == 0)
return "Graph is empty";
String result = new String("");
result += "Adjacency Matrix\n";
result += "----------------\n";
result += "index\t";
for (int i = 0; i < numVertices; i++)
{
result += "" + i;
if (i < 10)
result += " ";
}
result += "\n\n";
for (int i = 0; i < numVertices; i++)
{
result += "" + i + "\t";
for (int j = 0; j < numVertices; j++)
{
if (adjMatrix[i][j])
result += "1 ";
else
result += "0 ";
}
result += "\n";
}
result += "\n\nVertex Values";
result += "\n-------------\n";
result += "index\tvalue\n\n";
for (int i = 0; i < numVertices; i++)
{
result += "" + i + "\t";
result += vertices[i].toString() + "\n";
}
result += "\n";
return result;
}
/**
* Inserts an edge between two vertices of the graph.
*
* @param index1 the first index
* @param index2 the second index
*/
public void addEdge(int index1, int index2)
{
if (indexIsValid(index1) && indexIsValid(index2))
{
adjMatrix[index1][index2] = true;
adjMatrix[index2][index1] = true;
modCount++;
}
}
/**
* Removes an edge between two vertices of the graph.
*
* @param index1 the first index
* @param index2 the second index
*/
public void removeEdge(int index1, int index2)
{
// To be completed as a Programming Project
if (indexIsValid(index1) && indexIsValid(index2)) {
adjMatrix[index1][index2] = false;
adjMatrix[index2][index1] = false;
modCount--;
}
}
/**
* Inserts an edge between two vertices of the graph.
*
* @param vertex1 the first vertex
* @param vertex2 the second vertex
*/
public void addEdge(T vertex1, T vertex2)
{
addEdge(getIndex(vertex1), getIndex(vertex2));
}
/**
* Removes an edge between two vertices of the graph.
*
* @param vertex1 the first vertex
* @param vertex2 the second vertex
*/
public void removeEdge(T vertex1, T vertex2)
{
// To be completed as a Programming Project
removeEdge(getIndex(vertex1), getIndex(vertex2));
}
/**
* Adds a vertex to the graph, expanding the capacity of the graph
* if necessary.
*/
public void addVertex()
{
// To be completed as a Programming Project
if (numVertices == vertices.length)
expandCapacity();
vertices[numVertices] = null;
for (int i = 0; i <= numVertices; i++)
{
adjMatrix[numVertices][i] = false;
adjMatrix[i][numVertices] = false;
}
numVertices++;
}
/**
* Adds a vertex to the graph, expanding the capacity of the graph
* if necessary. It also associates an object with the vertex.
*
* @param vertex the vertex to add to the graph
*/
public void addVertex(T vertex)
{
if ((numVertices + 1) == adjMatrix.length)
expandCapacity();
vertices[numVertices] = vertex;
for (int i = 0; i < numVertices; i++)
{
adjMatrix[numVertices][i] = false;
adjMatrix[i][numVertices] = false;
}
numVertices++;
modCount++;
}
/**
* Removes a vertex at the given index from the graph. Note that
* this may affect the index values of other vertices.
*
* @param index the index at which the vertex is to be removed from
*/
public void removeVertex(int index)
{
// To be completed as a Programming Project
if (indexIsValid(index))
{
numVertices--;
for (int i = index; i < numVertices; i++)
vertices[i] = vertices[i+1];
for (int i = index; i < numVertices; i++)
for (int j = 0; j <= numVertices; j++)
adjMatrix[i][j] = adjMatrix[i+1][j];
for (int i = index; i < numVertices; i++)
for (int j = 0; j < numVertices; j++)
adjMatrix[j][i] = adjMatrix[j][i+1];
}
}
/**
* Removes a single vertex with the given value from the graph.
*
* @param vertex the vertex to be removed from the graph
*/
public void removeVertex(T vertex)
{
// To be completed as a Programming Project
for (int i = 0; i < numVertices; i++)
{
if (vertex.equals(vertices[i]))
{
removeVertex(i);
return;
}
}
}
/**
* Returns an iterator that performs a depth first traversal
* starting at the given index.
*
* @param startIndex the index from which to begin the traversal
* @return an iterator that performs a depth first traversal
*/
public Iterator<T> iteratorDFS(int startIndex)
{
Integer x;
boolean found;
StackADT<Integer> traversalStack = new LinkedStack<Integer>();
UnorderedListADT<T> resultList = new ArrayUnorderedList<T>();
boolean[] visited = new boolean[numVertices];
if (!indexIsValid(startIndex))
return resultList.iterator();
for (int i = 0; i < numVertices; i++)
visited[i] = false;
traversalStack.push(new Integer(startIndex));
resultList.addToRear(vertices[startIndex]);
visited[startIndex] = true;
while (!traversalStack.isEmpty())
{
x = traversalStack.peek();
found = false;
//Find a vertex adjacent to x that has not been visited
// and push it on the stack
for (int i = 0; (i < numVertices) && !found; i++)
{
if (adjMatrix[x.intValue()][i] && !visited[i])
{
traversalStack.push(new Integer(i));
resultList.addToRear(vertices[i]);
visited[i] = true;
found = true;
}
}
if (!found && !traversalStack.isEmpty())
traversalStack.pop();
}
return new GraphIterator(resultList.iterator());
}
/**
* Returns an iterator that performs a depth first search
* traversal starting at the given vertex.
*
* @param startVertex the vertex to begin the search from
* @return an iterator that performs a depth first traversal
*/
public Iterator<T> iteratorDFS(T startVertex)
{
return iteratorDFS(getIndex(startVertex));
}
/**
* Returns an iterator that performs a breadth first
* traversal starting at the given index.
*
* @param startIndex the index from which to begin the traversal
* @return an iterator that performs a breadth first traversal
*/
public Iterator<T> iteratorBFS(int startIndex)
{
Integer x;
QueueADT<Integer> traversalQueue = new LinkedQueue<Integer>();
UnorderedListADT<T> resultList = new ArrayUnorderedList<T>();
if (!indexIsValid(startIndex))
return resultList.iterator();
boolean[] visited = new boolean[numVertices];
for (int i = 0; i < numVertices; i++)
visited[i] = false;
traversalQueue.enqueue(new Integer(startIndex));
visited[startIndex] = true;
while (!traversalQueue.isEmpty())
{
x = traversalQueue.dequeue();
resultList.addToRear(vertices[x.intValue()]);
//Find all vertices adjacent to x that have not been visited
// and queue them up
for (int i = 0; i < numVertices; i++)
{
if (adjMatrix[x.intValue()][i] && !visited[i])
{
traversalQueue.enqueue(new Integer(i));
visited[i] = true;
}
}
}
return new GraphIterator(resultList.iterator());
}
/**
* Returns an iterator that performs a breadth first search
* traversal starting at the given vertex.
*
* @param startVertex the vertex to begin the search from
* @return an iterator that performs a breadth first traversal
*/
public Iterator<T> iteratorBFS(T startVertex)
{
return iteratorBFS(getIndex(startVertex));
}
/**
* Returns an iterator that contains the indices of the vertices
* that are in the shortest path between the two given vertices.
*
* @param startIndex the starting index
* @param targetIndex the the target index
* @return the an iterator containing the indices of the
* of the vertices making the shortest path between
* the given indices
*/
protected Iterator<Integer> iteratorShortestPathIndices
(int startIndex, int targetIndex)
{
int index = startIndex;
int[] pathLength = new int[numVertices];
int[] predecessor = new int[numVertices];
QueueADT<Integer> traversalQueue = new LinkedQueue<Integer>();
UnorderedListADT<Integer> resultList =
new ArrayUnorderedList<Integer>();
if (!indexIsValid(startIndex) || !indexIsValid(targetIndex) ||
(startIndex == targetIndex))
return resultList.iterator();
boolean[] visited = new boolean[numVertices];
for (int i = 0; i < numVertices; i++)
visited[i] = false;
traversalQueue.enqueue(new Integer(startIndex));
visited[startIndex] = true;
pathLength[startIndex] = 0;
predecessor[startIndex] = -1;
while (!traversalQueue.isEmpty() && (index != targetIndex))
{
index = (traversalQueue.dequeue()).intValue();
//Update the pathLength for each unvisited vertex adjacent
// to the vertex at the current index.
for (int i = 0; i < numVertices; i++)
{
if (adjMatrix[index][i] && !visited[i])
{
pathLength[i] = pathLength[index] + 1;
predecessor[i] = index;
traversalQueue.enqueue(new Integer(i));
visited[i] = true;
}
}
}
if (index != targetIndex) // no path must have been found
return resultList.iterator();
StackADT<Integer> stack = new LinkedStack<Integer>();
index = targetIndex;
stack.push(new Integer(index));
do
{
index = predecessor[index];
stack.push(new Integer(index));
} while (index != startIndex);
while (!stack.isEmpty())
resultList.addToRear(((Integer)stack.pop()));
return new GraphIndexIterator(resultList.iterator());
}
/**
* Returns an iterator that contains the shortest path between
* the two vertices.
*
* @param startIndex the starting index
* @param targetIndex the target index
* @return an iterator that contains the shortest path
* between the given vertices
*/
public Iterator<T> iteratorShortestPath(int startIndex,
int targetIndex)
{
UnorderedListADT<T> resultList = new ArrayUnorderedList<T>();
if (!indexIsValid(startIndex) || !indexIsValid(targetIndex))
return resultList.iterator();
Iterator<Integer> it = iteratorShortestPathIndices(startIndex,
targetIndex);
while (it.hasNext())
resultList.addToRear(vertices[((Integer)it.next()).intValue()]);
return new GraphIterator(resultList.iterator());
}
/**
* Returns an iterator that contains the shortest path between
* the two vertices.
*
* @param startVertex the starting vertex
* @param targetVertex the target vertex
* @return an iterator that contains the shortest path between
* the given vertices
*/
public Iterator<T> iteratorShortestPath(T startVertex, T targetVertex)
{
return iteratorShortestPath(getIndex(startVertex),
getIndex(targetVertex));
}
/**
* Returns the weight of the least weight path in the network.
* Returns positive infinity if no path is found.
*
* @param startIndex the starting index
* @param targetIndex the target index
* @return the integer weight of the least weight path
* in the network
*/
public int shortestPathLength(int startIndex, int targetIndex)
{
int result = 0;
if (!indexIsValid(startIndex) || !indexIsValid(targetIndex))
return 0;
int index1, index2;
Iterator<Integer> it = iteratorShortestPathIndices(startIndex,
targetIndex);
if (it.hasNext())
index1 = ((Integer)it.next()).intValue();
else
return 0;
while (it.hasNext())
{
result++;
it.next();
}
return result;
}
/**
* Returns the weight of the least weight path in the network.
* Returns positive infinity if no path is found.
*
* @param startVertex the starting vertex
* @param targetVertex the target vertex
* @return the integer weight of teh least weight path
* in the network
*/
public int shortestPathLength(T startVertex, T targetVertex)
{
return shortestPathLength(getIndex(startVertex), getIndex(targetVertex));
}
/**
* Returns a minimum spanning tree of the graph.
*
* @return a minimum spanning tree of the graph
*/
public Graph getMST()
{
int x, y;
int[] edge = new int[2];
StackADT<int[]> vertexStack = new LinkedStack<int[]>();
Graph<T> resultGraph = new Graph<T>();
if (isEmpty() || !isConnected())
return resultGraph;
resultGraph.adjMatrix = new boolean[numVertices][numVertices];
for (int i = 0; i < numVertices; i++)
for (int j = 0; j < numVertices; j++)
resultGraph.adjMatrix[i][j] = false;
resultGraph.vertices = (T[])(new Object[numVertices]);
boolean[] visited = new boolean[numVertices];
for (int i = 0; i < numVertices; i++)
visited[i] = false;
edge[0] = 0;
resultGraph.vertices[0] = this.vertices[0];
resultGraph.numVertices++;
visited[0] = true;
// Add all edges that are adjacent to vertex 0 to the stack.
for (int i = 0; i < numVertices; i++)
{
if (!visited[i] && this.adjMatrix[0][i])
{
edge[1] = i;
vertexStack.push(edge.clone());
visited[i] = true;
}
}
while ((resultGraph.size() < this.size()) && !vertexStack.isEmpty())
{
// Pop an edge off the stack and add it to the resultGraph.
edge = vertexStack.pop();
x = edge[0];
y = edge[1];
resultGraph.vertices[y] = this.vertices[y];
resultGraph.numVertices++;
resultGraph.adjMatrix[x][y] = true;
resultGraph.adjMatrix[y][x] = true;
visited[y] = true;
// Add all unvisited edges that are adjacent to vertex y
// to the stack.
for (int i = 0; i < numVertices; i++)
{
if (!visited[i] && this.adjMatrix[i][y])
{
edge[0] = y;
edge[1] = i;
vertexStack.push(edge.clone());
visited[i] = true;
}
}
}
return resultGraph;
}
/**
* Creates new arrays to store the contents of the graph with
* twice the capacity.
*/
protected void expandCapacity()
{
T[] largerVertices = (T[])(new Object[vertices.length*2]);
boolean[][] largerAdjMatrix =
new boolean[vertices.length*2][vertices.length*2];
for (int i = 0; i < numVertices; i++)
{
for (int j = 0; j < numVertices; j++)
{
largerAdjMatrix[i][j] = adjMatrix[i][j];
}
largerVertices[i] = vertices[i];
}
vertices = largerVertices;
adjMatrix = largerAdjMatrix;
}
/**
* Returns the number of vertices in the graph.
*
* @return the integer number of vertices in the graph
*/
public int size()
{
// To be completed as a Programming Project
return numVertices;
}
/**
* Returns true if the graph is empty and false otherwise.
*
* @return true if the graph is empty
*/
public boolean isEmpty()
{
// To be completed as a Programming Project
return (numVertices == 0);
}
/**
* Returns true if the graph is connected and false otherwise.
*
* @return true if the graph is connected
*/
public boolean isConnected()
{
// To be completed as a Programming Project
if (isEmpty())
return false;
Iterator<T> it = iteratorBFS(0);
int count = 0;
while (it.hasNext())
{
it.next();
count++;
}
return (count == numVertices);
}
/**
* Returns the index value of the first occurrence of the vertex.
* Returns -1 if the key is not found.
*
* @param vertex the vertex whose index value is being sought
* @return the index value of the given vertex
*/
public int getIndex(T vertex)
{
// To be completed as a Programming Project
for (int i = 0; i < numVertices; i++)
if (vertices[i].equals(vertex))
return i;
return -1;
}
/**
* Returns true if the given index is valid.
*
* @param index the index whose validity is being queried
* @return true if the given index is valid
*/
protected boolean indexIsValid(int index)
{
// To be completed as a Programming Project
return ((index < numVertices) && (index >= 0));
}
/**
* Returns a copy of the vertices array.
*
* @return a copy of the vertices array
*/
public Object[] getVertices()
{
// To be completed as a Programming Project
Object[] vertices = new Object[numVertices];
Object vertex;
for (int i = 0; i < numVertices; i++)
{
vertex = this.vertices[i];
vertices[i] = vertex;
}
return vertices;
}
/**
* Inner class to represent an iterator over the elements of this graph
*/
protected class GraphIterator implements Iterator<T>
{
private int expectedModCount;
private Iterator<T> iter;
/**
* Sets up this iterator using the specified iterator.
*
* @param iter the list iterator created by a graph traversal
*/
public GraphIterator(Iterator<T> iter)
{
this.iter = iter;
expectedModCount = modCount;
}
/**
* Returns true if this iterator has at least one more element
* to deliver in the iteration.
*
* @return true if this iterator has at least one more element to deliver
* in the iteration
* @throws ConcurrentModificationException if the collection has changed
* while the iterator is in use
*/
public boolean hasNext() throws ConcurrentModificationException
{
if (!(modCount == expectedModCount))
throw new ConcurrentModificationException();
return (iter.hasNext());
}
/**
* Returns the next element in the iteration. If there are no
* more elements in this iteration, a NoSuchElementException is
* thrown.
*
* @return the next element in the iteration
* @throws NoSuchElementException if the iterator is empty
*/
public T next() throws NoSuchElementException
{
if (hasNext())
return (iter.next());
else
throw new NoSuchElementException();
}
/**
* The remove operation is not supported.
*
* @throws UnsupportedOperationException if the remove operation is called
*/
public void remove()
{
throw new UnsupportedOperationException();
}
}
/**
* Inner class to represent an iterator over the indexes of this graph
*/
protected class GraphIndexIterator implements Iterator<Integer>
{
private int expectedModCount;
private Iterator<Integer> iter;
/**
* Sets up this iterator using the specified iterator.
*
* @param iter the list iterator created by a graph traversal
*/
public GraphIndexIterator(Iterator<Integer> iter)
{
this.iter = iter;
expectedModCount = modCount;
}
/**
* Returns true if this iterator has at least one more element
* to deliver in the iteration.
*
* @return true if this iterator has at least one more element to deliver
* in the iteration
* @throws ConcurrentModificationException if the collection has changed
* while the iterator is in use
*/
public boolean hasNext() throws ConcurrentModificationException
{
if (!(modCount == expectedModCount))
throw new ConcurrentModificationException();
return (iter.hasNext());
}
/**
* Returns the next element in the iteration. If there are no
* more elements in this iteration, a NoSuchElementException is
* thrown.
*
* @return the next element in the iteration
* @throws NoSuchElementException if the iterator is empty
*/
public Integer next() throws NoSuchElementException
{
if (hasNext())
return (iter.next());
else
throw new NoSuchElementException();
}
/**
* The remove operation is not supported.
*
* @throws UnsupportedOperationException if the remove operation is called
*/
public void remove()
{
throw new UnsupportedOperationException();
}
}
}
这是我到目前为止的驱动程序：
//tests the adjacency matrix implementation of a graph
public class GraphTest {
public static void main(String[] args) {
Graph first = new Graph();
first.toString();
}
}
当我运行它时，它应该输出“Graph is empty”但输出完全空白。为什么会这样？
答案 0 :(得分：1)
您没有向控制台输出任何内容。尝试：
public class GraphTest {
public static void main(String[] args) {
Graph first = new Graph();
System.out.println( first.toString() );
}
}