Queue Operations In Java - Using Reference As Pointer
May 28, 2014I am trying to run the queue operations in java such as enqueue, dequeue using pointers ... How to use references as pointer in java.
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AWT Event Queue Null Pointer Exception While Using JRE 1.7.51 As IE Browser
Feb 17, 2014My web application will load an applet with SWING components (Menu bar) on successful login to application.
Once page is loaded, i choose a menu item from the menu bar and click on it. Dynamic menu bar is loaded for the selected menu item. After that i am not able to perform any action on menu bar. Ending up with below error.
Note: My Application is absolutely working fine till JRE 1.7.17. But when i upgarde to higher version of JRE like 1.7.25 and above i am getting below error.
Exception in thread "AWT-EventQueue-4" java.lang.NullPointerException
at javax.swing.RepaintManager.scheduleProcessingRunna ble(Unknown Source)
at javax.swing.RepaintManager.addDirtyRegion0(Unknown Source)
at javax.swing.RepaintManager.addDirtyRegion(Unknown Source)
at javax.swing.JComponent.repaint(Unknown Source)
at java.awt.Component.repaint(Unknown Source)
[Code] ....
Remove All Numbers From Queue And Push Onto Stack Until Operator Is Reached - Null Pointer Exception
Apr 26, 2015This 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());
[Code] .....
Dequeue Of Queue Implemented Using Circular Singly Linked List With No Tail Reference
Oct 27, 2014So I'm trying to build a queue, first in first out, (so add to the head remove from the end) using a linked list for use in another program, I'm having a problem dequeueing where the program seems to run indefinitely without giving an answer, so my suspicion is its caught in a while loop but how and why I can't figure out.
public class CircularQueuelist {
private Node head = null;
private int size = 0;
private class Node
{
int data;
Node next;
[Code] ....
My logic seems sound, I basically look for when the second node over from the current one I'm on is a reference to the head, and then skip the one in front of it using setting currents. next link to current.next = head, severing the link to the last node.
This is what my driver looks like, I enqueue items 1-10 and then use the iterator to make sure it worked out fine and check size, its when I dequeue that I run into a problem, the program runs indefinitely.
public class Queuetest {
public static void main(String[]args)
{
CircularQueuelist test = new CircularQueuelist();
for (int count = 0; count < 10; count ++)
[Code] ....
Simulate Simple Calculator That Performs Basic Arithmetic Operations Of JAVA
Sep 9, 2014How can i write a java program that simulate a simple calculator that performs the basic arithmetic operations of JAVA. (JOption Pane and Repeat control structure)
Example : Addition, Subtraction, Multiplication, Division.
The program will prompt to input two floating point numbers and a character that represents the operations presented above. In the event that the operator input is valid, prompt the user to input the operator again.
Sample Output :
First number 7
Second number 4
Menu
<+> Addition
<-> Subtraction
<*> Multiplication
</> Division
Enter Choice: * <enter>
The answer is 28.
JSF :: Java Lang Null Pointer Exception In Webservices
Apr 2, 2014i have a j sf application that is using web-services to communicate to another application and pass some parameters to it.The application has three methods one to call the webservice,another to insert some values into a database and the third method to call the two methods when i click a button in a form.The methods a are
update() this is for calling a webservice and passing parameters to it.
insertt() to in sert to a database.
all() to call the above two.
when i call upadate and insertt in all method am getting an error java lang null pointer exception but when i call just one of the methods it executes successfully.This is my code package softmint.com;
import java.sql.Connection;
//import java.sql.Date;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
//import java.text.SimpleDateFormat;
import javax.xml.ws.WebServiceRef;
[code]....
Points To Ponder For Java Null Pointer Exceptions
Dec 12, 2014This is what I wrote and I get this eror : Points to Ponder for Java Null Pointer Exceptions
public class Line{
private Punkt2d pStart;
private Punkt2d pEnde;
public Line(Punkt2d pStart, Punkt2d pEnde) {
this.pStart = pStart;
this.pEnde= pEnde;
[Code] ....
Erorr:
Exception in thread "main" java.lang.NullPointerException
at Line.getLength(Line.java:38)
at Aufgabe_6_1.main(Aufgabe_6_1.java:7)
Queue Class And Java LinkedList
Sep 30, 2014I 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;
[Code] ......
Java And Passing By Reference
Nov 12, 2014I know in C++ It's possible to pass by reference but what about java?
For example, can i pass the address of a health variable into a Ninja class and then
Since Ninja inherits from an enemy class pass the health into the enemy class and within there have a function that returns that same health address and takes 5 from the health returning 95.
Priority Queue In Java Which Keeps Track Of Each Node Position
May 4, 2014I'm working on a lab for my class. I need to create a Priority Queue in Java using an array list. The kicker is that each node has to have a "handle" which is just an object which contains the index of of the node that it's associated with. I know that sounds weird but we have to implement it this way. Anyway, my priority queue seem to work fine except the handle values apparently aren't updating correctly because I fail the handle test. Also, I run into problems with handles only after extractMin() is called, so I figured the problem would be somewhere in that method but I've been through it a million times and it looks good to me.
Here is my Priority Queue Class:
package lab3;
import java.util.ArrayList;
/**
* A priority queue class supporting operations needed for
* Dijkstra's algorithm.
*/
class PriorityQueue<T> {
final static int INF = 1000000000;
ArrayList<PQNode<T>> queue;
[Code] ....
I can post the tests too but I don't know if that would do much good. Just know that the queue works as is should, but the handles don't point to the right nodes after extractMin() is utilized.
Final Reference Variables In Java
Feb 28, 2015I am unable to understand the meaning of this sentence "final reference variables must be initialized before the constructor completes.",What is trying to imply?
View Replies View RelatedPossibility To Use Pass By Reference Technique In Java
Aug 27, 2014if there is a possibility to use the pass by reference technique in java like in C++.URL....
View Replies View RelatedSwing/AWT/SWT :: Getting JFrame Reference Into Java Bean Using RMI?
May 21, 2014I got a project at my university , and we are working with JBoss with the free version WildFly .And also with Java EE.
Now the application is a simple game of Battle Ships or sinking ships to be honest i am not sure as to how the game is actually called.
Registering a user and saving his or her information is not hard using a Stateless java bean , to save the data in the database.
I have a Stateful java bean for every user , the bean is created on the server side after the user succeeds in logging in to the game.
This bean is used mainly for sending an invite from one user to another , to log out the user and everything else that is needed for the user.
The main problem that i encountered here is that JBoss dose not let me have a reference on my frame inside of the bean.
This makes things hard because i would need to use a Timer to ask the bean every second or so if there is an invite from someone , and i would need to save all of the invites .
This was the only thing i could think of .And also implementing the game it self , the communication between users would be complicated more so than i think its needed.
Then my professor said that i could make a service on the clients side in witch i would have a reference of the JFrame , and i could send this service to the java bean and using this service i could get access to the JFrame making things faster.
This would make things a lot easier.For the invite and for the game itself too.
My professor explained that JBoss or WildFly is based on RMI , and he said also that i would need to set up the registry on the server side .But i got lost because i was not sure as to what should i search for .
We are using an older version of WildFly not the newest but one version older , CR1 i think.
And we are also using JPA in the Dynamic web project , server .
Java-8 :: Method Reference Does Not Work With Decorator Pattern
Mar 28, 2014I faced with a problem, when I use method reference as a function in Collectors.groupingBy I get an error: "no suitable method found for collect". But! if I replaced method reference with a lambda expression everything works fine.
Here is the code sample:
interface Iface{
public int getPropertyOfClassA();
public void setPropertyOfClassA(int propertyOfClassA);
}
class A implements Iface{
private int propertyOfClassA;
[Code] ....
Change "C::getPropertyOfClassA" with "objC -> objC.getPropertyOfClassA()" and it works!
How To Count Primitive Operations
May 2, 2014I have having some trouble on counting the primitive operations on the pseudocode given below:
Algorithm 4. MaximumArray(Arr)
Input: A 1-D numerical array Arr of size n
1) Let CurrentMax = a0
2) For i = 1 to n-1
3)If ai > CurrentMax Then CurrentMax = ai
4) End For
Output: CurrentMax, the largest value in Arr
As of now, I know that for Line 1 there are 2 operations (one set and one read). I don't know how to figure out the for loop and If statement (line 2 and line 3 too).
Nested Loops Or Set Operations?
Oct 10, 2013Is there any advantage to using Java's operations defined in sets or collections over inspecting in nested for-loops?
For example, suppose I want to keep items from one array that do not appear in another, I could do:
for( PrimitiveType prim_1 : someArray ){
for( PrimitiveType prim_2 : otherArray ){
if( prim_1 != prim_2){
///put in some return list
}
}
}
Or else I could do:
ArrayList<NotPrimitive> excludedElements =
new ArrayList(Arrays.asList(primitiveArrayToExclude));
for( PrimitiveType elem : someArray){
if( ! excludedElements.contains( elem ) {
//put in some return list
}
}
I personally see no improvement in legibility nor any reduction of error potential.....
I/O / Streams :: Any Way To Parallel I/O Operations
Jul 31, 2014I've been wondering about this for a while. Is there any way to parallel I/O operations or is this a bad idea? If you could create two lists of good and bad ways to parallelize I/O.
View Replies View RelatedUsing A Menu For Stack Operations
Dec 3, 2014I am working on implementing a stack using a linked list. Programming the stack operations (push, pop, isEmpty, etc.) was easy but my directions were to provide the user with a menu to choose the operation that he/she wishes to perform. I am new to JFrames/Menus so how to make the stack operations available in a menu.
View Replies View RelatedIllegal Start Of Operations For All Methods
Apr 21, 2015Where are all these illegal start of operations and all of these other method errors coming from.I've written enough methods not to have this problem.
----jGRASP exec: javac -g Assessement.java
Assessement.java:29: error: illegal start of expression
public void addQuestionAnswer(){
^
Assessement.java:29: error: illegal start of expression
[code].....
How To Compute All Possible Arithmetic Operations Of 4 Integers
Nov 25, 2014I'm new to Java and I want to write a program that compute all the possible arithmetic operations of 4 integers.
For example, if the user enter 1, 2, 3, and 4 respectively, then I want the computer to print out the following results:
1 + 2 + 3 + 4
1 + 2 + 3 - 4
1 + 2 + 3 * 4
1 + 2 + 3 / 4
..
1 / 2 / 3 / 4
(parenthesis can be ignored for this program)
This is what I have so far, but I don't know how to continue:
import java.util.Scanner;
public class ArithmeticComputation{
public static void main(String[] args) {
Scanner stdin = new Scanner(System.in);
int num1 = stdin.nextInt();
[Code] ....
I'm looking for a method that allows me to assign char into actual operators, so that I can loop through all the computation.
LISP Expression - Performing Operations
Jan 29, 2015Given a LISP expression, perform operations on the expression. There will be no list elements that also contain a list such as '(A (B (C D))), which has one atom and one list but the list contains a sublist
INPUT: There will be 5 lines of input. Each line will contain a valid LISP expression. There will be a space between each atom and each list. There are no spaces immediately after or immediately before parentheses in a list. The entire expression must be inputted as a single string.
OUPUT: Perform the given operation on the like numbered expression. The 5 operations are:
1. Print the expression with the list in reverse order. The list will contain only atoms.
2. Print the expression with the list written with consecutive duplicates encoded as sublists in (count element) order. The list will contain only atoms.
3 Print the expression with the list written with consecutive duplicates encoded as sublists in (count element) order except that singletons are listed as atoms. The list will contain only atoms.
4. Print the expression with the list written with every Nth element deleted and where N is the last element of the list.
5. Print the expression written as 2 expressions where the number of lists in first expression is the last element of the expression.
SAMPLE INPUT SAMPLE OUTPUT
1. '(A B C D) 1. ′(D C B A)
2. '(A A A A B C C A A D E E E E) 2. ′((4 A) (1 B) (2 C) (2 A) (1 D) (4 E))
3. '(A A A A B C C A A D E E E E) 3. ′((4 A) B (2 C) (2 A) D (4 E))
4. '((4 A) (1 B) (2 C) (2 A) (1 D) (4 E) 2) 4. ′((4 A) (2 C) (1 D) 2)
5. '((4 A) (1 B) (2 C) (2 A) (1 D) (4 E) 3) 5. ′((4 A) (1 B) (2 C)) ′((2 A) (1 D) (4 E) 3)
Unchecked Or Unsafe Operations While Compiling Program?
Jun 30, 2014String filename="C:UsersRajashekarDesktopfwfwdSoftware Failures1_Test.txt";//Input Files
String data;
public ArrayList<String> value=new ArrayList<String>();
public void read() throws IOException{
File f = new File(filename);
[Code] ....
What Are Interleaving Operations - Can Atomic Actions Interleave
Mar 24, 2014I have read that when two threads have two steps (of execution) and each step involves many operations, then the operations of both the threads kind of overlap one-another. For example
I think I am not very clear about interleaving actions/operations? Especially when we say that atomic actions can not be interleaved. But
Java Code:
class Counter{
private int c=0;
void increment () {
c++;
}
void readIn () {
[Code] ....
And the following sequence of events occurs.
Thread A: Retrieve cThread A: Increment cThread A: Store the result in cThread B: Ask the user to enter a valueThread B: Read in the value, store it in c
Now the value of c obtained after increment will be lost (Thread Interference). Isn't this an example of interleaving operations?
JSP Calculator - Performing Basic Operations On Numbers
Jul 8, 2014I want a simple jsp page that performs basic operations on numbers such as addition, subtraction, multiplication, division and modulus . How to run that file?
View Replies View RelatedJavaFX 2.0 :: Perform Boolean Operations On 3D Primitives?
Nov 10, 2014How to perform boolean operations (union, intersect and subtract) on 3D primitives in javafx 3D?
View Replies View RelatedSwing/AWT/SWT :: How To Code Button That Get Selected Element From JComboBox And Perform Operations
Aug 6, 2014i've spend an hour or two, pasting fragments from tutorials and nothing changed.
Well - i have GUI, that have JComboBox with two elements:
String[] fedoras = { "Fedora 19", "Fedora 20" };
JComboBox fedora_list = new JComboBox(fedoras);
fedora_list.setSelectedIndex(0);
fedora_list.setBounds(120,170, 170,25);
fedora_list.addActionListener(this);
this.add(fedora_list);
Below i have normal button (named Update) with "update" set as ActionCommand. This button after clicked should check which value from list is selected and perform different operations for that elements. But it's harder than i thought.
Code for update button:
public void actionPerformed(ActionEvent e){
String cmd = e.getActionCommand();
(...)
else if ("update".equals(cmd)){
String selectedFedora = (String) fedora_list.getSelectedItem();
if (selectedFedora.equals("Fedora 19")) {
[code]....
- after user clicked Update button, button should check which value is selected in JComboBox (fedora_list).
- if Fedora 19 is selected and button clicked, then action in Xterm
- if Fedora 20 is selected, this same action in Xterm is performed, but for Fedora Linux 20
The problem is - i don't know hot to code Update button to check which value from fedora_list (JComboBox) is selected and perform other actions for every element on List.