Question
Start with the file LList2.java and add the following methods: Add the method int getLastIndex(T item) that returns the index of the last entry which
Start with the file LList2.java and add the following methods:
Add the method
int getLastIndex(T item)
that returns the index of the last entry which is equal to item. If item is not found, it returns -1. (15 points)
Add the method
int removeEvery(T item) that removes all occurrences of item and returns the number of removed items. (15 points)
Add the method
boolean equals(Object other) method that returns true when the contents of 2 LList2 objects are the same (the two objects in this case are the current object and other). Note that 2 LList2 objects are the same if they have the same number of items and each item in one object exists in the same location in the other object (15 points)
Provide a second implementation of the method
boolean contains2(T anEntry)
that calls a private recursive method
private boolean contains(T anEntry, Node startNode)
that returns whether the list that starts at startNode contains the entry anEntry. (10 points)
LList2.java
public class LList2
{
private Node firstNode; // head reference to first node
private Node lastNode; // tail reference to last node
private int numberOfEntries;
public LList2()
{
clear();
} // end default constructor
public final void clear() // NOTICE clear is not final in interface and that is OK
{
firstNode = null;
lastNode = null;
numberOfEntries = 0;
} // end clear
public void add(T newEntry) // OutOfMemoryError possible
{
Node newNode = new Node(newEntry); // create new node
if (isEmpty())
firstNode = newNode;
else
lastNode.setNextNode(newNode);
lastNode = newNode;
numberOfEntries++;
} // end add
public boolean add(int newPosition, T newEntry) // OutOfMemoryError possible
{
boolean isSuccessful = true;
if ((newPosition >= 1) && (newPosition <= numberOfEntries + 1))
{
Node newNode = new Node(newEntry);
if (isEmpty())
{
firstNode = newNode;
lastNode = newNode;
}
else if (newPosition == 1)
{
newNode.setNextNode(firstNode);
firstNode = newNode;
}
else if (newPosition == numberOfEntries + 1)
{
lastNode.setNextNode(newNode);
lastNode = newNode;
}
else
{
Node nodeBefore = getNodeAt(newPosition - 1);
Node nodeAfter = nodeBefore.getNextNode();
newNode.setNextNode(nodeAfter);
nodeBefore.setNextNode(newNode);
} // end if
numberOfEntries++;
}
else
isSuccessful = false;
return isSuccessful;
} // end add
public T remove(int givenPosition)
{
T result = null; // return value
if ((givenPosition >= 1) && (givenPosition <= numberOfEntries))
{
assert !isEmpty();
if (givenPosition == 1) // case 1: remove first entry
{
result = firstNode.getData(); // save entry to be removed
firstNode = firstNode.getNextNode();
if (numberOfEntries == 1)
lastNode = null; // solitary entry was removed
}
else // case 2: givenPosition > 1
{
Node nodeBefore = getNodeAt(givenPosition - 1);
Node nodeToRemove = nodeBefore.getNextNode();
Node nodeAfter = nodeToRemove.getNextNode();
nodeBefore.setNextNode(nodeAfter); // disconnect the node to be removed
result = nodeToRemove.getData(); // save entry to be removed
if (givenPosition == numberOfEntries)
lastNode = nodeBefore; // last node was removed
} // end if
numberOfEntries--;
} // end if
return result; // return removed entry, or
// null if operation fails
} // end remove
public boolean replace(int givenPosition, T newEntry)
{
boolean isSuccessful = true;
if ((givenPosition >= 1) && (givenPosition <= numberOfEntries))
{
assert !isEmpty();
Node desiredNode = getNodeAt(givenPosition);
desiredNode.setData(newEntry);
}
else
isSuccessful = false;
return isSuccessful;
} // end replace
public T getEntry(int givenPosition)
{
T result = null; // result to return
if ((givenPosition >= 1) && (givenPosition <= numberOfEntries))
{
assert !isEmpty();
result = getNodeAt(givenPosition).getData();
} // end if
return result;
} // end getEntry
public boolean contains(T anEntry)
{
boolean found = false;
Node currentNode = firstNode;
while (!found && (currentNode != null))
{
if (anEntry.equals(currentNode.getData()))
found = true;
else
currentNode = currentNode.getNextNode();
} // end while
return found;
} // end contains
public int getLength()
{
return numberOfEntries;
} // end getLength
public boolean isEmpty()
{
boolean result;
if (numberOfEntries == 0) // or getLength() == 0
{
assert firstNode == null;
result = true;
}
else
{
assert firstNode != null;
result = false;
} // end if
return result;
} // end isEmpty
public T[] toArray()
{
// the cast is safe because the new array contains null entries
@SuppressWarnings("unchecked")
T[] result = (T[])new Object[numberOfEntries]; // warning: [unchecked] unchecked cast
int index = 0;
Node currentNode = firstNode;
while ((index < numberOfEntries) && (currentNode != null))
{
result[index] = currentNode.getData();
currentNode = currentNode.getNextNode();
index++;
} // end while
return result;
} // end toArray
// Returns a reference to the node at a given position.
// Precondition: List is not empty; 1 <= givenPosition <= numberOfEntries.
private Node getNodeAt(int givenPosition)
{
assert (firstNode != null) && (1 <= givenPosition) && (givenPosition <= numberOfEntries);
Node currentNode = firstNode;
if (givenPosition == numberOfEntries)
currentNode = lastNode;
else if (givenPosition > 1) // traverse the chain to locate the desired node
{
for (int counter = 1; counter < givenPosition; counter++)
currentNode = currentNode.getNextNode();
} // end if
assert currentNode != null;
return currentNode;
} // end getNodeAt
// Lab 3
// Problem 1
int getIndex(T item) {
return 0;
}
// Problem 2
int removeEvery(T item) {
return 0;
}
// Problem 3
boolean equals(Object other) {
return false;
}
//Problem 4
boolean contains2(T anEntry) {
return false;
}
private boolean contains(T anEntry, Node startNode) {
return false;
}
private class Node
{
private T data; // data portion
private Node next; // next to next node
private Node(T dataPortion)// PRIVATE or PUBLIC is OK
{
data = dataPortion;
next = null;
} // end constructor
private Node(T dataPortion, Node nextNode)// PRIVATE or PUBLIC is OK
{
data = dataPortion;
next = nextNode;
} // end constructor
private T getData()
{
return data;
} // end getData
private void setData(T newData)
{
data = newData;
} // end setData
private Node getNextNode()
{
return next;
} // end getNextNode
private void setNextNode(Node nextNode)
{
next = nextNode;
} // end setNextNode
} // end Node
} // end LList2
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