test&lab

DataLabs/lab4/LinkedBag.java

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+/**
+    A class of bags whose entries are stored in a chain of linked nodes.
+    The bag is never full.
+    @author Frank M. Carrano
+    @version 4.0
+*/
+public final class LinkedBag<T> implements BagInterface<T>
+{
+	private Node firstNode;       // Reference to first node
+	private int numberOfEntries;
+
+	public LinkedBag()
+	{
+		firstNode = null;
+      numberOfEntries = 0;
+	} // end default constructor
+
+	/** Adds a new entry to this bag.
+	    @param newEntry  The object to be added as a new entry.
+	    @return  True. */
+	public boolean add(T newEntry) // OutOfMemoryError possible
+	{
+      // Add to beginning of chain:
+		Node newNode = new Node(newEntry);
+		newNode.next = firstNode;  // Make new node reference rest of chain
+                                 // (firstNode is null if chain is empty)
+      firstNode = newNode;       // New node is at beginning of chain
+		numberOfEntries++;
+      
+		return true;
+	} // end add
+
+	/** Retrieves all entries that are in this bag.
+       @return  A newly allocated array of all the entries in this bag. */
+	public T[] toArray()
+	{
+      // The cast is safe because the new array contains null entries.
+      @SuppressWarnings("unchecked")
+      T[] result = (T[])new Object[numberOfEntries]; // Unchecked cast
+      
+      int index = 0;
+      Node currentNode = firstNode;
+      while ((index < numberOfEntries) && (currentNode != null))
+      {
+         result[index] = currentNode.data;
+         index++;
+         currentNode = currentNode.next;
+      } // end while
+      
+      return result;
+      // Note: The body of this method could consist of one return statement,
+      // if you call Arrays.copyOf
+	} // end toArray
+   
+	/** Sees whether this bag is empty.
+       @return  True if the bag is empty, or false if not. */
+	public boolean isEmpty()
+	{
+		return numberOfEntries == 0;
+	} // end isEmpty
+   
+	/** Gets the number of entries currently in this bag.
+       @return  The integer number of entries currently in the bag. */
+	public int getCurrentSize()
+	{
+		return numberOfEntries;
+	} // end getCurrentSize
+   
+// STUBS:
+
+	/** Removes one unspecified entry from this bag, if possible.
+       @return  Either the removed entry, if the removal
+                was successful, or null. */
+	public T remove()
+   {
+        T top = firstNode.data;
+        firstNode = firstNode.next;
+
+        numberOfEntries--;
+        return top;
+   } // end remove
+   
+	/** Removes one occurrence of a given entry from this bag.
+       @param anEntry  The entry to be removed.
+       @return  True if the removal was successful, or false otherwise. */
+   public boolean remove(T anEntry)
+   {
+      return false; // STUB
+   } // end remove
+	
+	/** Removes all entries from this bag. */
+	public void clear()
+   {
+      // STUB
+   } // end clear
+	
+	/** Counts the number of times a given entry appears in this bag.
+		 @param anEntry  The entry to be counted.
+		 @return  The number of times anEntry appears in the bag. */
+	public int getFrequencyOf(T anEntry)
+   {
+      return 0; // STUB
+   } // end getFrequencyOf
+	
+	/** Tests whether this bag contains a given entry.
+		 @param anEntry  The entry to locate.
+		 @return  True if the bag contains anEntry, or false otherwise. */
+	public boolean contains(T anEntry)
+   {
+      return false; // STUB
+   } // end contains
+
+	private class Node
+	{
+	  private T    data; // Entry in bag
+	  private Node next; // Link to next node
+
+		private Node(T dataPortion)
+		{
+			this(dataPortion, null);	
+		} // end constructor
+		
+		private Node(T dataPortion, Node nextNode)
+		{
+			data = dataPortion;
+			next = nextNode;	
+		} // end constructor
+	} // end Node
+} // end LinkedBag1
+
+
+