I'm trying to create a class that takes an String from a Stack and checking if it's a palindrome than taking a another String from a queue and checking if that is also a palindrome.
import java.util.Stack;
public class Palindrome {
public static void main(String[] args) {
// TODO Auto-generated method stub
String enteredLine;
int leftStack, rightStack;
int leftQueue, rightQueue;
PalinedromeArray stack1 = new PalinedromeArray();
The question is write to a method symmetric that accepts a stack of integers as a parameter and replaces the stack contents with itself plus a symmetrical version of itself (the same elements in the opposite order).
For example, suppose a variable s stores the following elements: bottom [10, 50, 19, 54, 30, 67] top
After a call of symmetric(s),the stack would store the following elements bottom [10, 50, 19, 54, 30, 67, 67, 30, 54, 19, 50, 10] top
Note that the symmetric version is added on to the top of what was originally in the stack. The bottom half of the stack contains the original numbers in the same order.
If your method is passed an empty stack, the result should be an empty stack. If your method is passed a null stack, your method should throw an IllegalArgumentException.
a) Write the method symmetric using one temporary stack and one temporary queue. /> Re-write the method using only one temporary Queue.
What I have done so far is
public static Stack symmetric(Stack s1){ Stack s2 =new Stack(); int theTop=0; if(s1.isEmpty()){ return s1;
I'm doing an assignment where a method receives a Queue as a parameter then convert it into a stack, I made it but now I want to try it in my main, but how can I do this? there's no toString and I cant use a for loop because I'm using a queue and not an array. This is the head of my method:
I want to create java program in which i want to inherit stack and queue from a linked list class and also make infix to postfix inherit from stack and periority queue from queue class.Ho can i make this program.
This method keeps throwing a NullPointerException. Not only that, but its not doing what I want it to do.
Heres the code:
/* Remove all the numbers from the queue and push onto the stack until an operator is reached */
private static void processQueue() { // Check what is at the front of the queue. If an operator is found or the queue is empty, exit method. while(queue.front() != null || !queue.front().equals("*") || !queue.front().equals("/") || !queue.front().equals("%") || !queue.front().equals("+") || !queue.front().equals("-")) { stack.push(queue.removeFront()); // push the operand onto the stack } }
Here is the method that calls the processQueue() method
/* Process the mathematical expression using a stack and a queue */ private static double processExpression() { // insert all elements from the stack to the queue for processing while(stack.top() != null) { queue.insertBack(stack.pop());
I have written a piece of code that takes a desired input file and calculates things such as words, characters, digits etc. I would like to make the program look better by counting palindromes.what I could add to my current code to count palindromes.My current code for counting other things that I would like to add plaindromes to.
// Loops through the file calculating the outcome. while (input.hasNextLine()) { lines++; String line = input.nextLine(); chars += line.length();
public static int reverse(int number) //return true if a palindrome public static Boolean isPalindrome(int number)
When I compile it says it cannot find symbol "remainder".
import java.util.*; public class PalindromeInteger { public static void main(String[] args) { //Create a scanner Scanner input = new Scanner(System.in);
I just started studying recursion and I wanted to know how to create a palindrome number going up from 1 to n then back to 1 like this: "12345...n...54321".
I've done one going downwards and then upwards like this: "n...4321234...n".
Here's my code:
Java Code: import java.util.*; public class PalindromeTest { public static void downPalindrome(int n)
Is it possible to define the same message driven bean as a listener to different queues?
The goal being to define different redelivery configuration for different kind of messages, but handle them all through a single deployment MDB for unity/entity purposes.
The other option is to have many MDBs targeted to the same source code.
leaveQ method does not work..To see the other files related to these code click here:(Its a dropbox location) URL....Java Code:
public class CustomerQ { private int MaxLength; private int totalCustomers;//assuming #of customers served int Qlength; Customer cus; LinkedList4Q cus4Q;
I am doing a bank queue simulator program which will figure what will happen in 100 minute where 0 to 2 customers comes every minute. 3 counters will handle these customers each counter will poll the customer after 3 minutes.my problem is queue.poll()is not working in counter method and it is adding null values to the queue in the same method. when i add while customers.isEmpty(); the program will not work i do not know why
package dataalgo; import java.util.LinkedList; import java.util.PriorityQueue; import java.util.Queue; import java.util.Random; public class customer {
import java.util.*; public class DoubleEndedQueueImplHW22 { ArrayList<Integer> deque = new ArrayList<Integer>(); public void insertFront(int a){ System.out.println("adding at front: "+a); deque.add(0,a); System.out.println(deque);
The following codes shows an implementation of an enqueue function of a FIFO immutable queue, and the output result shows the String "c".
I don't understand why since I expected it should be null.
The head and the tail of an ImmutableQueue Object are two separate queue, and each time I call the enqueue function, it just return a new object with a new tail, however, the head is not modified except the first two times I call the function.
Therefore, I expected head.next.next should be a null element, but the result is not like that.
public class ImmutableQueue<E> { private int size =0; public Queue<E> head; public Queue<E> tail; public ImmutableQueue(){} private ImmutableQueue(Queue<E> hd, Queue<E> tl){ head=hd; tail=tl;
I have a class "ExecuteJob" which has Print Q in the form of Priority Q.
You can keep adding job to the Q by calling one of the method in the class. However, and object cant do things simultaneity can it? While im adding a new job to the print queue, can it be executing and existing job in the print Q.
To achieve that, I would need to implement process and threads? I believe am I right? So that adding a job is independent to being removed?
I am new to Java/OOP in general, and am trying to implement a multi-threaded system that contains a master thread, and a set of worker threads that are heterogeneous in the work they do. Once they complete the work, the workers indicate to the master by posting the result on to its queue. Here is the problem. The results of each type of work is different, and the master has to process each differently. In C (which I'm familiar with), this can be achieved by having a message type that is a union of all the expected messages, and by using a switch statement.
I thought of doing something similar in Java, by using instance of on each incoming message (each individual message class having been subclassed from a super message class) , and doing switch on that, but it doesn't seem to be the OO way to do things. The only other way I could think of was to implement an abstract method to get the type of each message, and then use the type in a switch statement, or if-then-else. Is there some other Java idiom to do this kind of processing? Also, if this is an acceptable method, why is it superior to using the reflection to find out the message type (instead of using the abstract getType())?
The message types look similar to the code below:
abstract class Message { abstract String getType(); } class Result1 extends Message { ResultType1 content; String getType() {
I am in the process of implementing Priority queue, as I understand that there are many data structures you could use to implement. I implemented it with the an array, which it works absolutely fine. However I have limitations on what collections I can use from the collections classes. I fact I cant use any of the collections classes. Meaning I cant use array.
I’m trying to implement Priority Queue using heap. And implementing heap using binary trees. But however I have a few questions which I need to clarify and I cant think of any other way of resolving it. Ofcourse I can implement my own simple array class using linked list.
Inserting into heap would be quite simple, as I just need to find the right last position from left to right leaf to insert the node into the tree. However after inserting, you may want to make sure that leaf node values are > than root node. Therefore, the root node will always be with the highest priority.
I call these steps where you compare from top down as bubbledown and bubbleup. To do this I really need a for each node within the treee node to have attribute pointing to its root node. So in case of bubbleup I always have a pointer for a given node to its root, without it would mean I would to traverse through the entire tree to identify its root. Which I believe is very inefficient.
Or have I taken this completely wrong? Or is it the case that heap are only best with arrays and therefore use array (by implement it using linked list?)
I have situation where a user can request java server to send a value to an embedded device, and if the device is asleep, that value needs to be stored in a queue until the device wakes up and sends a position to java server, at which point the server checks if there is a value in the queue and if there is, it then sends that value to the device. The maximum size of the queue is 1 for now. And if the user makes continuous requests to java server, the old value is removed and the new value is added.
Initially I was looking into BlockingQueue, but the problem with that is, well, it blocks. queue.put(value) will block if queue is full, and queue.take() will block if queue is empty. I can't have something that blocks. When the device responds to server, server checks if value is in queue, if it is not then the server carries on the rest of its responsibility. Thus, I then entertained ConcurrentLinkedQueue. While queue.offer(value) and queue.poll(); allow you to add and remove values respectively from the queue without blocking, it does not allow you to set a maximum size limit of the queue. My queue must have a maximum size limit and it has to always be the newest value the user submits to the queue (where old values are removed).So this is what I came up with:
Java Code: class Unit { private List<Integer> cmdQueue;
public Unit(){ cmdQueue = Collections.synchronizedList(new LinkedList<Integer>());
[code]....
I use Collections.synchronizedList, as I do here, do I still need to use synchronize as I did above?
I have been working on this Java Gui program and i cant get it to print to the textbox correctly.i originally had it displayed in a dialog window but it would print one integer a time in a seperate window.
So I got an interesting challenge today. I think logically I know what I have to do but I'm at a complete loss as for the actual coding implementation. So I have to develop this method called moveToBack(T entry). What this is meant to do is as implies, move entry to the back of my queue. As simple as it sounds, I know that I cant just move its position that simple. I know that I'll have to essentially remove whatever the desired value is, and then re-add it to the back of the queue. The interesting problem with this, however; is that I know that the FIFO property exists for queue's.
So if the desired entry to be moved is at the 3rd position of 4, I'd have to remove positions 1 and 2 to finally get to 3. But I want it to keep those values still. So I assume what I'll have to do is remove each element of the queue (it'll only be 5 entries max for the purpose of the project) and save it somewhere, then empty the queue and finally add the elements back in while waiting and putting the desired element to the last position.
If that's the case, I'm really curious on how I would do this. I have 4 files, 2 interfaces, the main class that contains the methods and what not for the queue, and a 4th class that'll be used for running test data and testing the methods of the program. Now, I wont add the interfaces code below because those are fine and all methods that need to be added are. I just gotta improve my moveToBack method so that it does what its supposed to. (I know I should have exceptions instead of my very poor else statements, but for this project it's not necessary.)
public abstract class NoDuplicatesQueueWilson<T> implements NoDuplicatesQueueInterfaceWilson<T> { private int MAX_QUEUE = 5; // Default array size, small for testing purposes private T[] items; // The array of the queue. private int front; // The first entered item of a queue. private int back; // The last entered item of a queue. private int count; // A counter.
The following codes shows an implementation of an enqueue function of a FIFO immutable queue, and the output result shows the String "c". I don't understand why since I expected it should be null.
The head and the tail of an ImmutableQueue Object are two separate queue, and each time I call the enqueue function, it just return a new object with a new tail, however, the head is not modified except the first two times I call the function.
Therefore, I expected head.next.next should be a null element, but the result is not like that.
public class ImmutableQueue<E> { public Queue<E> head; public Queue<E> tail; public ImmutableQueue(){} private ImmutableQueue(Queue<E> hd, Queue<E> tl){ head=hd; tail=tl;
I have a Queue class (containing a LinkedList plus a few other variables and stats for my project), which works fine with the standard LinkedList, but I'm trying to add my own code for MyLinkedList.
However, I keep getting a NullPointerException at my remove method.
public class MyLinkedList<T> { Node head; public MyLinkedList() { head = null; } public class Node { T contents; Node nextNode;
I am looking for the ability, on the server side, to run programs or "jobs" in a job queue, where the jobs are processed as first in first out. If you are familiar with the IBM iSeries, they have a built in job queue mechanism which accomplishes what I am looking for. The primary purposes for this would be to process and update large amounts of data in a thread safe environment.
