first off i'm a college student. i'm not that good at java... we got this CA in class and try as i might i just can't get my head around it
i was wondering if someone who know a bit more about java then i do would point me in the right direction, were i'm going wrong in my code
i have to list out sub-files and sub-directorys of a folder (i.e. C:/test) to console using tree structure
like this
startingdir
dir1 //subfolder of startingdir
dir11 //subfolder of dir1
dir111 //subfolder of dir11
dir12 //subfolder of dir1
file1A // document on dir1
dir2 //subfolder of startingdir
Tree.java
import java.util.Iterator;
import java.util.LinkedList;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.Deque;
public class Tree<E> {
// Each Tree object is an unordered tree whose
// elements are arbitrary objects of type E.
// This tree is represented by a reference to its root node (root), which
// is null if the tree is empty. Each tree node contains a link to its
// parent and a LinkedList of child nodes
private Node root;
//////////// Constructor ////////////
public Tree () {
// Construct a tree, initially empty.
root = null;
}
//////////// Accessors ////////////
public boolean isEmpty () {
// Return true is and only if this tree is empty.
return (root == null);
}
public Node root () {
// Return the root node of this tree, or null if this tree is empty.
return root;
}
public Node parent (Node node) {
// Return the parent of node in this tree, or null if node is the root node.
return node.parent;
}
public void makeRoot (E elem) {
// Make this tree consist of just a root node containing element elem.
root = new Node(elem);
}
public Node addChild (Node node, E elem) {
// Add a new node containing element elem as a child of node in this
// tree. The new node has no children of its own. Return the node
// just added.
Node newChild = new Node(elem);
newChild.parent = node;
node.children.addLast(newChild);
return newChild;
}
public E element (Node node) {
return node.getElement();
}
//////////// Iterators ////////////
public Iterator childrenIterator (Node node) {
return node.children.iterator();
}
public Iterator nodesPreOrder () {
// Return an iterator that visits all nodes of this tree, with a pre-order
// traversal.
return new Tree.PreOrderIterator();
}
//////////// Inner classes ////////////
public class Node {
// Each Tree.Node object is a node of an
// unordered tree, and contains a single element.
// This tree node consists of an element (element),
// a link to its parent
// and a LinkedList of its children
private E element;
private Node parent;
private LinkedList<Node> children;
private Node (E elem) {
// Construct a tree node, containing element elem, that has no
// children and no parent.
this.element = elem;
this.parent = null;
children = new LinkedList<Node>();
}
public E getElement () {
// Return the element contained in this node.
return this.element;
}
public String toString () {
// Convert this tree node and all its children to a string.
String children = "";
// write code here to add all children
return element.toString() + children;
}
public void setElement (E elem) {
// Change the element contained in this node to be elem.
this.element = elem;
}
}
public class PreOrderIterator implements Iterator {
private Deque<Node> track; //Java recommends using Deque rather
// than Stack. This is used to store sequence of nomempty subtrees still
//to be visited
private PreOrderIterator () {
track = new LinkedList();
if (root != null)
track.addFirst(root);
}
public boolean hasNext () {
return (! track.isEmpty());
}
public E next () {
Node place = track.removeFirst();
//stack the children in reverse order
if (!place.children.isEmpty()) {
int size = place.children.size(); //number of children
ListIterator<Node> lIter =
place.children.listIterator(size); //start iterator at last child
while (lIter.hasPrevious()) {
Node element = lIter.previous();
track.addFirst(element);
}
}
return place.element;
}
public void remove () {
throw new UnsupportedOperationException();
}
}
}
FileHierarchy.java
import java.io.File;
import java.util.Iterator;
public class FileHierarchy {
// Each FileHierarchy object describes a hierarchical collection of
// documents and folders, in which a folder may contain any number of
// documents and other folders. Within a given folder, all documents and
// folders have different names.
// This file hierarchy is represented by a tree, fileTree, whose elements
// are Descriptor objects.
private Tree fileTree;
//////////// Constructor ////////////
public FileHierarchy (String startingDir, int level) {
// Construct a file hierarchy with level levels, starting at
// startingDir
// Can initially ignore level and construct as many levels as exist
fileTree = new Tree();
Descriptor descr = new Descriptor(startingDir, true);
fileTree.makeRoot(descr);
int currentLevel = 0;
int maxLevel = level;
addSubDirs(fileTree.root(), currentLevel, maxLevel);
}
//////////// File hierarchy operations ////////////
private void addSubDirs(Tree.Node currentNode, int currentLevel,
int maxLevel) {
// get name of directory in currentNode
// then find its subdirectories (can add files later)
// for each subdirectory:
// add it to children of currentNode - call addChild method of Tree
// call this method recursively on each child node representing a subdir
// can initially ignore currentLevel and maxLevel
Descriptor descr = (Descriptor) currentNode.getElement();
File f = new File(descr.name);
File[] list = f.listFiles();
for (int i = 0; i < list.length; ++i) {
if (list.isDirectory()) {
File[] listx = null;
fileTree.addChild(currentNode, i);
if (list[i].list().length != 0) {
listx = list[1].listFiles();
addSubDirs(currentNode,i,1);
}
} else if (list[i].isFile()) {
fileTree.addChild(currentNode, i);
}
}
// The following code is sample code to illustrate how File class is
// used to get a list of subdirectories from a starting directory
// list now contains subdirs and files
// contained in dir descr.name
}
////////// Inner class for document/folder descriptors. //////////
private static class Descriptor {
// Each Descriptor object describes a document or folder.
private String name;
private boolean isFolder;
private Descriptor (String name, boolean isFolder) {
this.name = name;
this.isFolder = isFolder;
}
}
}
FileHierarchyTest.java
public class FileHierarchyTest {
private static Tree fileTree;
public static void main(String[] args) {
FileHierarchy test = new FileHierarchy ("//test", 1);
System.out.println(test.toString());
}
}