Linked lists - changing nodes
Hello,
I have a double linked list where I want to change one node to another and change its references at the same time.
The nodes are not together i.e. they do not appear in the list consectutively.
I need to swap like B and D - I have managed to do swaps like A and B, and C and D (that took a while).
Is this logic correct (I am using temporary nodes):
if(f1 != (f2 - 1))
Object temp = object1;
Object temp2 = object2;
object1.getPrevious().setNext(object2);
object2.getNext().setPrevious(object1);
object1.getNext().setPrevious(object2);
object2.getPrevious().setNext(object1);
object1.setPrevious(temp2.getPrevious());
object1.setNext(temp2.getNext());
object2.setPrevious(temp.getPrevious());
object2.setNext(temp.getNext());
If this logic is not correct then please only give hints as to why.
Cheers
Hello,
I have a double linked list where I want to change
one node to another and change its references at the
same time.
The nodes are not together i.e. they do not appear in
the list consectutively.
I need to swap like B and D - I have managed to do
swaps like A and B, and C and D (that took a while).
Is this logic correct (I am using temporary nodes):
if(f1 != (f2 - 1))
Object temp = object1;
Object temp2 = object2;
object1.getPrevious().setNext(object2);
object2.getNext().setPrevious(object1);
object1.getNext().setPrevious(object2);
object2.getPrevious().setNext(object1);
object1.setPrevious(temp2.getPrevious());
object1.setNext(temp2.getNext());
object2.setPrevious(temp.getPrevious());
object2.setNext(temp.getNext());
If this logic is not correct then please only give
hints as to why.
CheersI didn't check your logic, but I think that there are errors in it since I saw these lines:
object1.setPrevious(temp2.getPrevious());
object1.setNext(temp2.getNext());
object2.setPrevious(temp.getPrevious());
object2.setNext(temp.getNext()); temp and temp2 are not copies of object1 and object2. They are references to the same object, so when you do e.g. object1.getPrevious().setNext() you also change previous->next for temp.
temp == object1
temp2 == object2
Kaj
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}chuang7 wrote:
So i made a method to get the nth element of the list in the order I input it to the list.
* The node it is currently reading
private Node curr;
* The previous node it has read.
These ('curr' and 'prev') should be local variables in the methods that need them, not instance variables.
public void addFront(Object o)
while (curr != null){
prev = curr;
curr = curr.getNext();
blank.setNext(curr);At this point 'curr' is always null so this line is redundant.
public void addBack(Object o)You can reduce this method to two lines of code.
public boolean contains(Object o)
curr.setNext(curr.getNext());You are modifying the list inside the contains method?
for (int j=1; j<=i; j++){Rethink this loop.
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prev.setNext(null);
if(curr.getNext() ==null)
sum += "\n" + curr.getElement()+"->"+curr.getNext();
curr.setNext(null);
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Thanks in advance.Hi jverd,
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THE ERROR HAPPENS HERE ON THIS LINE list.insert(datum.name);
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if(list.isEmpty())
System.out.println("List is currently empty.");
else if (list.size() == 1)
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package cs321_assignment1;
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private Node head;
private int count;
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head = null;
count = 0;
public LinkedList(LinkedList rhs) { //Copy constructor
head = rhs.head;
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pointer = pointer.getNext();
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head = newNode;
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back.setNext(newNode);
count++;
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found = true;
else {
back = pointer;
pointer = pointer.getNext();
if(found)
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head = pointer.getNext();
count--;
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back.setNext(pointer.getNext());
count--;
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System.out.println("List is currently empty.");
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head = head.getNext();
n.setNext(null);
count--;
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if(count == 0)
return true;
else
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Node current = head;
while(current != null) {
System.out.println(current.getData());
current = current.getNext();
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public Node getHead() {return head;}
public void setHead(Node n) {head = n;}
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package cs321_assignment1;
public class Node {
private int data;
private Node next;
public Node() {next = null;}
public Node(int d) {
next = null;
data = d;
public int getData() {return data;}
public void setData(int newData) {data = newData;}
public Node getNext() {return next;}
public void setNext(Node newNode) {next = newNode;}
}I can't figure this out, and I really need some help. Hopefully after I solve this, the selection and insertion sorts will be a little simpler. Any help will really be appreciated. -
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Hello everyone,
[I hope I am in the right forum]
I am trying to learn how to implement Linked Lists with Java. I have written a small code and I would appreceate it a lot if any one would be kind enough to check if this code is really a linked list.
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/***** OUTPUT ***** OUTPUT ***** OUTPUT ***** OUTPUT *****
Hi i am data contained in Node 1.
Hi i am data contained in Node 2.
Hi i am data contained in Node 3.
Hi this is Node2 ========================>:myList@16f0472
This is the value of pointer of Node 1 ==>:myList@16f0472
Hi this is Node3 ========================>:myList@18d107f
This is the value of pointer of Node 2 ==>:myList@18d107f
Press any key to continue...
Thank you very much,
JMelsiHappy to advise. Here we go. :)
Firstly, you'll want to post your code in code tags. They make your code more legible, thus making it easier and therefore more likely that someone responds. ;)
Second, it would be more appropriate for class names (such as "myList") to start with an upper-case letter (such as "MyList"). Additionally, the class in question does not represent a whole list but instead a node, so you might want to call it "MyListNode" or something similar.
Strictly speaking, your code is definitely that of a linked list of nodes. For example, one could print all of the contents in your list with code like this:
myList node = ...; // assign to the first node
while (node!=null) // as long as there is a node
System.out.println(node.nodeData); // print the data in this node
node = node.pointer; // move on to the next node
}Note that, in the above code, I didn't have to know how many nodes were in your list or have any references to them beforehand. :) That's the power in the data structure you're creating.
Enjoy! -
How can I print out the contents of a linked list whose nodes are made up of Data Objects?
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Changing data in a linked list object.
hi,
i'm still pretty new to java, so bear with me if i am making stupid mistakes, heh.
i'm having trouble with changing data in an object stored in a singly-linked list. i've created a class that will store polynomials in sorted order (descending) in a singly-linked list. each linked list is one polynomial, and each node references to a polynomial object that stores two ints: the coefficient and the exponent of that term.
i'm having trouble when it comes to 'collecting like terms,' though. here's a rough skeleton of my code:
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private LinkedListItr Itr;
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} // this constructor sets up an empty linked list
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exponent = e;
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thanks for the reply...
i am sure that ((Polynomial)tester.retrieve()).getExp() will return an int equal to 'e.' i tried this:
System.out.println("e="+e);
System.out.println((Polynomial)tester.retrieve()).getExp());
if( e == ((Polynomial)tester.retrieve()).getExp() ){
this.coeff = ((Polynomial)tester.retrieve()).getCoeff() + c;
System.out.println( "this.coeff = " + this.coeff );
with that, the output showed that e and the getExp() output were the same. it also showed (as output) that this.coeff did change in value, but when i tried this:
System.out.println( ((Polynomial)tester.retrieve()).getCoeff() )
to check if the value changed within the object, it didn't. this.coeff changed, but the actual coeff variable in the object didn't.
any ideas? -
Splitting a Linked List at a Given Node, into Two Sublists??
My code just will not work!! Any help would be appreciated! My problem is in the last method SplitAt. These are the conditions set and my code:
Splitting a Linked List at a Given Node, into Two Sublists
a. Add the following as an abstract method to the class
LinkedListClass:
public void splitAt (LinkedListClass<T> secondList, T item);
//This method splits the list at the node with the info item into two sublists.
//Precondition: The list must exist.
//Postcondition: first and last point to the first and last nodes of the first sublist,
// respectively. secondList.first and secondList.last point to the first
// and last nodes of the second sublist.
Consider the following statements:
UnorderedLinkedList<Integer> myList;
UnorderedLinkedList<Integer> otherList;
Suppose myList points to the list with the elements 34, 65, 18, 39, 27, 89, and 12 (in this order). The statement
myList.splitAt(otherList, 18);
splits myList into two sublists: myList points to the list with elements 34 and 65, and otherList points to the sublist with elements 18, 39, 27, 89, and 12.
b. Provide the definition of the method splitAt in the class UnorderedLinkedList. Also write a program to test your method.
public class UnorderedLinkedList<T> extends LinkedListClass<T>
//Default constructor
public UnorderedLinkedList()
super();
//Method to determine whether searchItem is in
//the list.
//Postcondition: Returns true if searchItem is found
// in the list; false otherwise.
public boolean search(T searchItem)
LinkedListNode<T> current; //variable to traverse
//the list
boolean found;
current = first; //set current to point to the first
//node in the list
found = false; //set found to false
while (current != null && !found) //search the list
if (current.info.equals(searchItem)) //item is found
found = true;
else
current = current.link; //make current point to
//the next node
return found;
//Method to insert newItem in the list.
//Postcondition: first points to the new list
// and newItem is inserted at the
// beginning of the list. Also,
// last points to the last node and
// count is incremented by 1.
public void insertFirst(T newItem)
LinkedListNode<T> newNode; //variable to create the
//new node
newNode =
new LinkedListNode<T>(newItem, first); //create and
//insert newNode before
//first
first = newNode; //make first point to the
//actual first node
if (last == null) //if the list was empty, newNode is
//also the last node in the list
last = newNode;
count++; //increment count
//Method to insert newItem at the end of the list.
//Postcondition: first points to the new list and
// newItem is inserted at the end
// of the list. Also, last points to
// the last node and
// count is incremented by 1.
public void insertLast(T newItem)
LinkedListNode newNode; //variable to create the
//new node
newNode =
new LinkedListNode(newItem, null); //create newNode
if (first == null) //if the list is empty, newNode is
//both the first and last node
first = newNode;
last = newNode;
else //if the list is not empty, insert
//newNode after last
last.link = newNode; //insert newNode after last
last = newNode; //set last to point to the
//actual last node
count++;
}//end insertLast
//Method to delete deleteItem from the list.
//Postcondition: If found, the node containing
// deleteItem is deleted from the
// list. Also, first points to the first
// node, last points to the last
// node of the updated list, and count
// is decremented by 1.
public void deleteNode(T deleteItem)
LinkedListNode<T> current; //variable to traverse
//the list
LinkedListNode<T> trailCurrent; //variable just
//before current
boolean found;
if ( first == null) //Case 1; the list is empty
System.err.println("Cannot delete from an empty "
+ "list.");
else
if (first.info.equals(deleteItem)) //Case 2
first = first.link;
if (first == null) //the list had only one node
last = null;
count--;
else //search the list for the given info
found = false;
trailCurrent = first; //set trailCurrent to
//point to the first node
current = first.link; //set current to point to
//the second node
while (current != null && !found)
if (current.info.equals(deleteItem))
found = true;
else
trailCurrent = current;
current = current.link;
}//end while
if (found) //Case 3; if found, delete the node
count--;
trailCurrent.link = current.link;
if (last == current) //node to be deleted
//was the last node
last = trailCurrent; //update the value
//of last
else
System.out.println("Item to be deleted is "
+ "not in the list.");
}//end else
}//end else
}//end deleteNode
public void splitAt(LinkedListClass<T> secondList, T item)
LinkedListNode<T> current;
LinkedListNode<T> trailCurrent;
int i;
boolean found;
if (first==null)
System.out.println("Empty.");
first=null;
last=null;
count--;
else
current=first;
found=false;
i=1;
while(current !=null &&!found)
if(current.info.equals(secondList))
found= true;
else
trailCurrent=current;
i++;
if(found)
if(first==current)
first=first;
last=last;
count=count;
count=0;
else
first=current;
last=last;
last=null;
count = count- i+1;
count = i-1;
else
System.out.println("Item to be split at is "
+ "not in the list.");
first=null;
last=null;
count=0;
}I dont have a test program at all. The program is supposed to prompt for user input of numbers. (it does) Take the input and end at input of -999 (it does). Then it asks user where it wants to split list (it does). When I enter a number it does nothing after that. I am going to post updated code and see if that helps along with all the classes. Thanks!
This is the class to prompt:
import java.util.*;
public class Ch16_ProgEx6
static Scanner console = new Scanner(System.in);
public static void main(String[] args)
UnorderedLinkedList<Integer> list
= new UnorderedLinkedList<Integer>();
UnorderedLinkedList<Integer> subList =
new UnorderedLinkedList<Integer>();
Integer num;
System.out.println("Enter integers ending with -999.");
num = console.nextInt();
while (num != -999)
list.insertLast(num);
num = console.nextInt();
System.out.println();
System.out.println("list: ");
list.print();
System.out.println();
System.out.println("Length of list: " + list.length());
System.out.print("Enter the number at which to split list: ");
num = console.nextInt();
list.splitAt(subList, num);
System.out.println("Lists after splitting list");
System.out.print("list: ");
list.print();
System.out.println();
System.out.println("Length of list: " + list.length());
System.out.print("sublist: ");
subList.print();
System.out.println();
System.out.println("Length of sublist: " + subList.length());
}This is the ADT:
public interface LinkedListADT<T> extends Cloneable
public Object clone();
//Returns a copy of objects data in store.
//This method clones only the references stored in
//each node of the list. The objects that the
//list nodes point to are not cloned.
public boolean isEmptyList();
//Method to determine whether the list is empty.
//Postcondition: Returns true if the list is empty;
// false otherwise.
public void initializeList();
//Method to initialize the list to an empty state.
//Postcondition: The list is initialized to an empty
// state.
public void print();
//Method to output the data contained in each node.
public int length();
//Method to return the number of nodes in the list.
//Postcondition: The number of nodes in the list is
// returned.
public T front();
//Method to return a reference of the object containing
//the data of the first node of the list.
//Precondition: The list must exist and must not be empty.
//Postcondition: The reference of the object that
// contains the info of the first node
// is returned.
public T back();
//Method to return a reference of object containing
//the data of the last node of the list.
//Precondition: The list must exist and must not be empty.
//Postcondition: The reference of the object that
// contains the info of the last node
// is returned.
public boolean search(T searchItem);
//Method to determine whether searchItem is in the list.
//Postcondition: Returns true if searchItem is found
// in the list; false otherwise.
public void insertFirst(T newItem);
//Method to insert newItem in the list.
//Postcondition: newItem is inserted at the
// beginning of the list.
public void insertLast(T newItem);
//Method to insert newItem at the end of the list.
//Postcondition: newItem is inserted at the end
// of the list.
public void deleteNode(T deleteItem);
//Method to delete deleteItem from the list.
//Postcondition: If found, the node containing
// deleteItem is deleted from the
// list.
public void splitAt(LinkedListClass<T> secondList, T item);
}This is the linked list class:
import java.util.NoSuchElementException;
public abstract class LinkedListClass<T> implements LinkedListADT<T>
protected class LinkedListNode<T> implements Cloneable
public T info;
public LinkedListNode<T> link;
//Default constructor
//Postcondition: info = null; link = null;
public LinkedListNode()
info = null;
link = null;
//Constructor with parameters
//This method sets info pointing to the object to
//which elem points to and link is set to point to
//the object to which ptr points to.
//Postcondition: info = elem; link = ptr;
public LinkedListNode(T elem, LinkedListNode<T> ptr)
info = elem;
link = ptr;
//Returns a copy of objects data in store.
//This method clones only the references stored in
//the node. The objects that the nodes point to
//are not cloned.
public Object clone()
LinkedListNode<T> copy = null;
try
copy = (LinkedListNode<T>) super.clone();
catch (CloneNotSupportedException e)
return null;
return copy;
//Method to return the info as a string.
//Postcondition: info as a String object is
// returned.
public String toString()
return info.toString();
} //end class LinkedListNode
public class LinkedListIterator<T>
protected LinkedListNode<T> current; //variable to
//point to the
//current node in
//list
protected LinkedListNode<T> previous; //variable to
//point to the
//node before the
//current node
//Default constructor
//Sets current to point to the first node in the
//list and sets previous to null.
//Postcondition: current = first; previous = null;
public LinkedListIterator()
current = (LinkedListNode<T>) first;
previous = null;
//Method to reset the iterator to the first node
//in the list.
//Postcondition: current = first; previous = null;
public void reset()
current = (LinkedListNode<T>) first;
previous = null;
//Method to return a reference of the info of the
//current node in the list and to advance iterator
//to the next node.
//Postcondition: previous = current;
// current = current.link;
// A refrence of the current node
// is returned.
public T next()
if (!hasNext())
throw new NoSuchElementException();
LinkedListNode<T> temp = current;
previous = current;
current = current.link;
return temp.info;
//Method to determine whether there is a next
//element in the list.
//Postcondition: Returns true if there is a next
// node in the list; otherwise
// returns false.
public boolean hasNext()
return (current != null);
//Method to remove the node currently pointed to
//by the iterator.
//Postcondition: If iterator is not null, then the
// node that the iterator points to
// is removed. Otherwise the method
// throws NoSuchElementException.
public void remove()
if (current == null)
throw new NoSuchElementException();
if (current == first)
first = first.link;
current = (LinkedListNode<T>) first;
previous = null;
if (first == null)
last = null;
else
previous.link = current.link;
if (current == last)
last = first;
while (last.link != null)
last = last.link;
current = current.link;
count--;
//Method to return the info as a string.
//Postcondition: info as a String object is returned.
public String toString()
return current.info.toString();
} //end class LinkedListIterator
//Instance variables of the class LinkedListClass
protected LinkedListNode<T> first; //variable to store the
//address of the first
//node of the list
protected LinkedListNode<T> last; //variable to store the
//address of the last
//node of the list
protected int count; //variable to store the number of
//nodes in the list
//Default constructor
//Initializes the list to an empty state.
//Postcondition: first = null, last = null,
// count = 0
public LinkedListClass()
first = null;
last = null;
count = 0;
//Method to determine whether the list is empty.
//Postcondition: Returns true if the list is empty;
// false otherwise.
public boolean isEmptyList()
return (first == null);
//Method to initialize the list to an empty state.
//Postcondition: first = null, last = null,
// count = 0
public void initializeList()
first = null;
last = null;
count = 0;
//Method to output the data contained in each node.
public void print()
LinkedListNode<T> current; //variable to traverse
//the list
current = first; //set current so that it points to
//the first node
while (current != null) //while more data to print
System.out.print(current.info + " ");
current = current.link;
}//end print
//Method to return the number of nodes in the list.
//Postcondition: The value of count is returned.
public int length()
return count;
//Method to return a reference of the object containing
//the data of the first node of the list.
//Precondition: The list must exist and must not be empty.
//Postcondition: The reference of the object that
// contains the info of the first node
// is returned.
public T front()
return first.info;
//Method to return a reference of object containing
//the data of the last node of the list.
//Precondition: The list must exist and must not be empty.
//Postcondition: The reference of the object that
// contains the info of the last node
// is returned.
public T back()
return last.info;
//Returns a copy of objects data in store.
//This method clones only the references stored in
//each node of the list. The objects that the
//list nodes point to are not cloned.
public Object clone()
LinkedListClass<T> copy = null;
try
copy = (LinkedListClass<T>) super.clone();
catch (CloneNotSupportedException e)
return null;
//If the list is not empty clone each node of
//the list.
if (first != null)
//Clone the first node
copy.first = (LinkedListNode<T>) first.clone();
copy.last = copy.first;
LinkedListNode<T> current;
if (first != null)
current = first.link;
else
current = null;
//Clone the remaining nodes of the list
while (current != null)
copy.last.link =
(LinkedListNode<T>) current.clone();
copy.last = copy.last.link;
current = current.link;
return copy;
//Method to return an iterator of the list.
//Postcondition: An iterator is instantiated and
// returned.
public LinkedListIterator<T> iterator()
return new LinkedListIterator<T>();
//Method to determine whether searchItem is in
//the list.
//Postcondition: Returns true if searchItem is found
// in the list; false otherwise.
public abstract boolean search(T searchItem);
//Method to insert newItem in the list.
//Postcondition: first points to the new list
// and newItem is inserted at the
// beginning of the list. Also,
// last points to the last node and
// count is incremented by 1.
public abstract void insertFirst(T newItem);
//Method to insert newItem at the end of the list.
//Postcondition: first points to the new list and
// newItem is inserted at the end
// of the list. Also, last points to
// the last node and
// count is incremented by 1.
public abstract void insertLast(T newItem);
//Method to delete deleteItem from the list.
//Postcondition: If found, the node containing
// deleteItem is deleted from the
// list. Also, first points to the first
// node, last points to the last
// node of the updated list, and count
// is decremented by 1.
public abstract void deleteNode(T deleteItem);
public abstract void splitAt(LinkedListClass<T> secondList, T item);
}And this is the UnorderedLinked Class with the very last method the one being Im stuck on. The SplitAt Method.
public class UnorderedLinkedList<T> extends LinkedListClass<T>
//Default constructor
public UnorderedLinkedList()
super();
//Method to determine whether searchItem is in
//the list.
//Postcondition: Returns true if searchItem is found
// in the list; false otherwise.
public boolean search(T searchItem)
LinkedListNode<T> current; //variable to traverse
//the list
boolean found;
current = first; //set current to point to the first
//node in the list
found = false; //set found to false
while (current != null && !found) //search the list
if (current.info.equals(searchItem)) //item is found
found = true;
else
current = current.link; //make current point to
//the next node
return found;
//Method to insert newItem in the list.
//Postcondition: first points to the new list
// and newItem is inserted at the
// beginning of the list. Also,
// last points to the last node and
// count is incremented by 1.
public void insertFirst(T newItem)
LinkedListNode<T> newNode; //variable to create the
//new node
newNode =
new LinkedListNode<T>(newItem, first); //create and
//insert newNode before
//first
first = newNode; //make first point to the
//actual first node
if (last == null) //if the list was empty, newNode is
//also the last node in the list
last = newNode;
count++; //increment count
//Method to insert newItem at the end of the list.
//Postcondition: first points to the new list and
// newItem is inserted at the end
// of the list. Also, last points to
// the last node and
// count is incremented by 1.
public void insertLast(T newItem)
LinkedListNode newNode; //variable to create the
//new node
newNode =
new LinkedListNode(newItem, null); //create newNode
if (first == null) //if the list is empty, newNode is
//both the first and last node
first = newNode;
last = newNode;
else //if the list is not empty, insert
//newNode after last
last.link = newNode; //insert newNode after last
last = newNode; //set last to point to the
//actual last node
count++;
}//end insertLast
//Method to delete deleteItem from the list.
//Postcondition: If found, the node containing
// deleteItem is deleted from the
// list. Also, first points to the first
// node, last points to the last
// node of the updated list, and count
// is decremented by 1.
public void deleteNode(T deleteItem)
LinkedListNode<T> current; //variable to traverse
//the list
LinkedListNode<T> trailCurrent; //variable just
//before current
boolean found;
if ( first == null) //Case 1; the list is empty
System.err.println("Cannot delete from an empty "
+ "list.");
else
if (first.info.equals(deleteItem)) //Case 2
first = first.link;
if (first == null) //the list had only one node
last = null;
count--;
else //search the list for the given info
found = false;
trailCurrent = first; //set trailCurrent to
//point to the first node
current = first.link; //set current to point to
//the second node
while (current != null && !found)
if (current.info.equals(deleteItem))
found = true;
else
trailCurrent = current;
current = current.link;
}//end while
if (found) //Case 3; if found, delete the node
count--;
trailCurrent.link = current.link;
if (last == current) //node to be deleted
//was the last node
last = trailCurrent; //update the value
//of last
else
System.out.println("Item to be deleted is "
+ "not in the list.");
}//end else
}//end else
}//end deleteNode
public void splitAt(LinkedListClass<T> secondList, T item)
LinkedListNode<T> current;
LinkedListNode<T> trailCurrent;
int i;
boolean found;
if (first==null)
System.out.println("Empty.");
first=null;
last=null;
count--;
count=0;
else
current=first;
found=false;
i=1;
while(current !=null &&!found)
if(current.info.equals(item))
found= true;
else
trailCurrent=first;
current=first;
i++;
if(found)
if(first==current)
first.link=first;
last.link=last;
count--;
count=0;
else
first.link=current;
last.link=last;
last=null;
count = count- i+1;
count = i-1;
} else {
System.out.println("Item to be split at is "
+ "not in the list.");
first=null;
last=null;
count=0;
Any help or just advice would be fine. Im not the best at Java, better at VB. Am completely stumped! Thanks so much! -
Recursively Finding a Node in a Linked List
I'm trying to find a node recursively in this linked list but keep coming up with an error message - can anyone tell me what is wrong?
public boolean find (Object obj)
DonorNode node = new DonorNode(obj);
DonorNode current = list;
if (don.equals(current))
return true;
else
return find(current.next);
}Please post within code tags (button above the message box).
Without more information it's hard to say.
What is list?
What is don?
If you don't mind me pointing out:
A method named find conventionally returns some object it is searching for or null if not found.
What you have (by that I mean a method returning boolean) is generally named contains (or some other obvious predicate name).
That being said, if I assume that DonorNodes contain some Object and have getter functions to access those; and that list is a DonorNode representing the head of the list, try something like:public boolean contains(Object o) {
return contains(o, list);
private boolean contains(Object o, DonorNode n) {
if (n.getObject() == o)
return true;
if (n.getNext() == null)
return false;
return contains(o, n.getNext());
}Although keep in mind that comparing two Objects using '==' will result in reference only comparison. If you need some other form of comparison you might consider using the equals method (make sure you then implement it in all potentially contained classes) or even narrowing the accepted argument to classes that implement the Comparable interface.
Hope this helps. -
How do you change the font in WPC Link List Header ...
Does any one know how/where to change the font in Web Page Composer on the Link List Header? I am using the Link List header delivered with the product.
It looks like it is pulling arial font but we are adding content in a different font in the paragraphs and want the fonts to be the same. Is there something I can change in the theme?
thanks
Angie.You need to go to the
Content Adminstration/KM Content/etc/wpceditor/css/runtime and look in the sdn_general.css file. The controls are all there. You can rename or create a new style sheet as this will modify all WPC sites. -
Hi,
In a lecture a couple of weeks ago, we began the topic of reference-based lists. I copied the attached
code off the board. I'm now trying to utilize the code by creating a public class Node. However, the constructors don't seem to make much sense. I was too busy writing down the information to pay much attention at the time. My book doesn't seem to address this...
1) in the first constructor: item = null; I'm declaring item initially as an integer, but the constructor is trying to attach a null to item. I think the intent is to create a node that initially has both info and link as nulls.
2) in the third constructor: link = Node; Is this possible? I'm not what this will do.
And finally, the second and third constructors are using the same name and parameter, so there is a conflict. I don't know how to resolve this.
Thanks in advance for any help...
aiki
public class Node {
public int info;
public Node link;
public Node(){
info = null;
link = null;
public Node (int data){
info = data;
link = null;
public Node (int data){
info = data;
link = Node;public class Node {
public int info;
public Node link;
public Node(){
// default constructor does nothing.
// Therefore info and link will get default values.
// For Objects this will be null
public Node (int data){
info = data;
// don't initialise link. See above
public Node (int data, Node node){
// I think you missed the second parameter
info = data;
link = node;
} -
I have a binary B+tree.
I have done all the insertion..but I have a major problem as my current node is poiting to the last node I inserted node ...
In the class I have a parent node
I want to use this to go back to the root...but I fail..function is called from a tree class
in the function {
Node curr = this;
Node temp= this.parent;
while(temp!=null) {
temp= temp.parent;
if(temp!=null) {
curr=temp;
return curr;
However, this code doesn't work...
not sure why...
can anyone help me with this .. Thanks?carl33p wrote:
Might have to fill it manually unless anyone else has an idea.
...I have a few ideas:
- keep the logic from getting input from a user separate from your linked list
class: it is not the responsibility of a linked list to perform such tasks;
- create a separate class with a main method that instantiates a linked list
and gets the user input;
- don't name one of your classes the same as one of Java's "core" classes. When
you do "import java.util.*" you might get in trouble. Since you are only storing
int's in your list, a better name would be "IntLinkedList"
- create a method called add(int) that is responsible for the addition of new
nodes;
- create a private inner class for your Node class: you won't be needing this
Node outside of your IntLinkedList class, so there's no need for it to be
"visible" for other classes.
Here's a skeleton:
class Test {
private static int getUserInput() {
// Prompt the user to enter an integer and when
// a valid integer is entered, return it.
return -1;
public static void main(String[] args) {
IntLinkedList myList = new IntLinkedList();
int nodeCount = 5;
while(nodeCount-- > 0) {
int input = getUserInput();
myList.add(input);
System.out.println("myList = "+myList.toString());
class IntLinkedList {
private Node start;
public IntLinkedList() {
start = null;
public void add(int value) {
Node newNode = new Node(value);
// Your code here
// - what to do when 'start' equals null?
// - and what to do when 'start' does not equal null?
// more methods
private class Node {
int value;
Node next;
Node(int v) {
value = v;
next = null;
// more methods
} -
Help needed in linked lists...
I have been working on this computer assignment lately but I still don't understand linked lists yet..I did an assignment on array based implementation and now I am supposed to do the same thing in linked list implementation..
I need help on how to change this into a linked list implementation..any help would be appreciated. Thank you..below is the code for the array based implementation..the only thing that needs change here is after where is says Array-based implementation of the ADT list.
public class ListArrayBasedDriver {
public static void main(String [] args) {
ListArrayBased myGroceryList = new ListArrayBased();
myGroceryList.add(1,"milk");
myGroceryList.add(2,"eggs");
myGroceryList.add(3,"butter");
myGroceryList.add(4,"pecans");
myGroceryList.add(5,"apples");
myGroceryList.add(6,"bread");
myGroceryList.add(7,"chicken");
myGroceryList.add(8,"rice");
myGroceryList.add(9,"red beans");
myGroceryList.add(10,"sausage");
myGroceryList.add(11,"flour");
printList(myGroceryList); //print out original List
System.out.print("numItems is now: " + myGroceryList.size() + "\n");
System.out.println("adding juice for 5th item...");
myGroceryList.add (5, (Object) "juice"); //add juice
System.out.println("item 5 is: " + myGroceryList.get(5)); //get position 5
printList(myGroceryList);
System.out.print("numItems is now: " + myGroceryList.size() + "\n");
System.out.println("removing juice...");
myGroceryList.remove (5); //remove item at position 5
printList(myGroceryList);
System.out.print("numItems is now: " + myGroceryList.size() + "\n");
public static void printList(ListArrayBased myList)
//method prints a list, numbering the values, e.g, "1. milk" .... "5. juice".... etc.
int i;
for(i=1; i <= myList.size(); i++)
String tempString = new String((String)myList.get(i));
System.out.println(i+" "+ tempString);
// Array-based implementation of the ADT list.
class ListArrayBased {
private static final int MAX_LIST = 50;
private Object items[]; // an array of list items
private int numItems; // number of items in list
public ListArrayBased()
// creates an empty list
items = new Object[MAX_LIST];
numItems = 0;
} // end default constructor
public boolean isEmpty()
return (numItems == 0);
} // end isEmpty
public int size()
return numItems;
} // end size
public void removeAll()
// Creates a new array; marks old array for
// garbage collection.
items = new Object[MAX_LIST];
numItems = 0;
} // end removeAll
public void add(int index, Object item) throws ListIndexOutOfBoundsException
if (numItems > MAX_LIST)
throw new ListException("ListException on add");
} // end if
if (index >= 1 && index <= numItems+1)
// make room for new element by shifting all items at
// positions >= index toward the end of the
// list (no shift if index == numItems+1)
for (int pos = numItems; pos >= index; pos--) {
items[translate(pos+1)] = items[translate(pos)];
} // end for
// insert new item
items[translate(index)] = item;
numItems++;
else
{ // index out of range
throw new ListIndexOutOfBoundsException(
"ListIndexOutOfBoundsException on add");
} // end if
} //end add
public Object get(int index) throws ListIndexOutOfBoundsException
if (index >= 1 && index <= numItems)
return items[translate(index)];
else
{ // index out of range
throw new ListIndexOutOfBoundsException(
"ListIndexOutOfBoundsException on get");
} // end if
} // end get
public void remove(int index) throws ListIndexOutOfBoundsException
if (index >= 1 && index <= numItems)
// delete item by shifting all items at
// positions > index toward the beginning of the list
// (no shift if index == size)
for (int pos = index+1; pos <= size(); pos++) {
items[translate(pos-1)] = items[translate(pos)];
} // end for
numItems--;
else
{ // index out of range
throw new ListIndexOutOfBoundsException("ListIndexOutOfBoundsException on remove");
} // end if
} // end remove
private int translate(int position) {
return position - 1;
} // end translate
} // end ListArrayBased
class ListException extends RuntimeException
public ListException(String s)
super(s);
} // end constructor
} // end ListException
class ListIndexOutOfBoundsException
extends IndexOutOfBoundsException {
public ListIndexOutOfBoundsException(String s) {
super(s);
} // end constructor
} // end ListIndexOutOfBoundsExceptionCould someone check for me if this will work and if it doesn't what I need to do to make it work..Thanks...
public class ListArrayBasedDriver {
public static void main(String [] args) {
ListArrayBased myGroceryList = new ListArrayBased();
myGroceryList.add(1,"milk");
myGroceryList.add(2,"eggs");
myGroceryList.add(3,"butter");
myGroceryList.add(4,"pecans");
myGroceryList.add(5,"apples");
myGroceryList.add(6,"bread");
myGroceryList.add(7,"chicken");
myGroceryList.add(8,"rice");
myGroceryList.add(9,"red beans");
myGroceryList.add(10,"sausage");
myGroceryList.add(11,"flour");
printList(myGroceryList); //print out original List
System.out.print("numItems is now: " + myGroceryList.size() + "\n");
System.out.println("adding juice for 5th item...");
myGroceryList.add (5, (Object) "juice"); //add juice
System.out.println("item 5 is: " + myGroceryList.get(5)); //get position 5
printList(myGroceryList);
System.out.print("numItems is now: " + myGroceryList.size() + "\n");
System.out.println("removing juice...");
myGroceryList.remove (5); //remove item at position 5
printList(myGroceryList);
System.out.print("numItems is now: " + myGroceryList.size() + "\n");
public static void printList(ListArrayBased myList)
//method prints a list, numbering the values, e.g, "1. milk" .... "5. juice".... etc.
int i;
for(i=1; i <= myList.size(); i++)
String tempString = new String((String)myList.get(i));
System.out.println(i+" "+ tempString);
// Linked List-based implementation of the ADT list.
class ListNode
//class to represent one node in a list
class ListNode
//package access members; List can access these directly
Object data;
ListNode nextNode;
//contructor creates a ListNode that refers to object
ListNode( Object object)
this( object, null );
} //end ListNode one-argument constructor
//constructor creates ListNode that refers to
// Object and to the next ListNode
ListNode ( Object object, ListNode node)
data = object;
nextNode = node;
// end ListNode two-argument contructor
//return reference to data in node
Object getObject()
return data; // return Object in this mode
//return reference to next node in list
ListNode getNext()
return nextNode; // get next node
} // end method getNext
} //end class ListNode
//class List Definition
public class List
private ListNode firstNode;
private ListNode lastNode;
private String name; // string like " list " used in printing
//contructor creates empty List with " list " as the name
public List()
this(" list ");
} //end List no-arguement constructor
//contructor creates an empty list with a name
public List( String listName )
name = listname;
firstNode = lastNode = null;
} //end List no-arguement contructor
//insert Object at front of List
public void insertAtFront ( object insertItem )
if ( isEmpty() ) //firstNode and lastNode refer to same object
firstNode = lastNode = newListNode( insertItem );
else // firstNode refers to new node
firstNode = new ListNode ( insertItem, firstNode );
} // end method insertAtFront
// insert Object at end of List
public void insert AtBack ( Object insertItem )
if ( isEmpty() ) //firstNode and lastNode refer to same object
firstNode = new ListNode ( insertItem );
else // firstNode refers to new node
firstNode = new ListNode (insertItem, firstNode );
} // end method insertAtFront
// insert Object at end of List
public void insertAtBack ( Object insertItem )
if ( isEmpty() ) //firstNode and LastNode refer to same Object
firstNode = lastNode = new ListNode ( insertItem );
else // lastNode = lastNode.nextNode = new ListNode ( insertItem );
} // end method insertAtBack
//remove first node from List
public Object removeFromFront() throws EmptyListException
if( isEmpty() ) //throw exception if list is empty
throw new EmptyListException( name );
object removedItem = firstNode.data; //retrieve data being removed
// update references firstNode and lastNode
if (firstNode == lastNode )
firstNode =lastNode = null;
else
firstNode = firstNode.nextNode;
return removedItem; // return removed node data
} //end method removeFromFront
//remove last node from List
Public Object removeFromBack() throws EmptyListException
If ( isEmpty() ) // throw exception if list is empty
throw new EmptyListException( name );
Object removedItem = lastNode.data; // retrieve data being removed
// update references firstNode and lastNode
If ( firstNode == lastNode )
firstNode = lastNode = null;
else // locate new last node
ListNode current = firstNode;
// loop while current node does not refer to lastNode
while ( current.nextNode != lastNode )
current = current.nextNode;
lastNode = current; // current is new lastNode
current.nextNode = null;
} // end else
return removedItem; // return removed node data
} // end method removeFromBack
// determine whether list is empty
public boolean isEmpty()
return firstNode == null; // return true if list is empty
} // end method isEmpty
//output List contents
public void print()
if (isEmpty() )
System.out.printf(�Empty %s\n�, name );
return;
System.out.printf(�The %s is: �, name );
ListNode current = firstNode;
//while (current != null )
System.out,printf(�%s �, current.data );
current = current.nextNode;
} //end while
System.out.println( �\n� );
} //end method print
} end class List
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