Object Locking Mechanism Implementation?
Jul 21, 2014I want to implement new locking mechanism similar to like how threads locking or synchronized does the operation. Any inputs to implement out own locking mechanism ?
View Replies
ADVERTISEMENT
Object Level Locking In Java Threads
Apr 16, 2014I know that below code would put a lock on current instance of DemoClass, What I am not sure of is the role of lock on Object Class in second example. How does below works - Is it putting a lock on Object Class? If yes how will putting a lock on Object? I mean, locking DemoClass ensure no two threads access it concurrently, how does this apply to Object class?
private final Object lock = new Object();
synchronized (lock)
public class DemoClass
{
public void demoMethod(){
synchronized (this)
[code]....
Adding Mechanism For Strings
Oct 12, 2014Basically, there is a class "InfiniteInteger" which implements Comparable and can be used to store extremely long numbers as strings (i.e. "37493274839247923749234"). It has a couple functions such as "toString()", "compareTo()" and "isNegative()". Then there's the method I can't quite push through, "add(InfiniteInteger anInfiniteInteger)".Somewhere along the way, it just won't carry numbers correctly... It should work for positive and negative numbers but doesn't quite.
public InfiniteInteger plus(final InfiniteInteger anInfiniteInteger)
{
// TO DO
String number1 = new String(string).replaceAll("-", "");
String number2 = new String(anInfiniteInteger.string).replaceAll("-", "");
int[] firstDigits = new int[number1.length()];
int[] secondDigits = new int[number2.length()];
int place = 0;
for(int i = firstDigits.length - 1; i >= 0; i--) {
firstDigits[place] = Integer.parseInt(Character.toString(number1.charAt(i)));
place++;
}
place = 0;
for(int i = secondDigits.length - 1; i >= 0; i--) {
secondDigits[place] = Integer.parseInt(Character.toString(number2.charAt(i)));
[code]...
I can't use any external packages (i.e. Arrays, BigDecimal, ArrayList) and can't use long as a datatype either.
Servlets :: Multi Threading Mechanism?
Nov 16, 2014Is there any specific name for servlet's multi threading mechanism? I mean any technical term for it.
View Replies View RelatedLocking The Camera On Character?
Mar 2, 2015I finally made the app to draw 10x10 map out of 50x50 pixel blocks.Now I can't imagine how to make a camera and lock it on character. I know how to make a character, but I just want to understand how locking the camera on character would look.
package tiled;
import org.newdawn.slick.*;
import org.newdawn.slick.state.*;
public class play extends BasicGameState {
int xSize = 10;
int ySize = 10;
[code]....
JDBC Delete Command Locking Database?
Aug 27, 2014I have a problem where i cant seem to get this simple delete command working. Everytime i run it it just locks the database and crashes
The id parameter exists in the database the database is small. Only a few tables. update commands work completely fine.
The id is an in and resulting command is - DELETE from Employees where ID = 2;
public static void EmployeeDeleteByID(int idIn){
Connection c = null;
Statement stmt = null;
try {
c = Connect();
c.setAutoCommit(false);
System.out.println("Opened database successfully");
[code]....
Error after running : java.sql.SQLException: database is locked
JSP :: Check Box Implementation
Sep 30, 20141. In jsp 1 , i have 3 checkboxes(chkbox1,chkbox2,chkbox3) , if i select check boxes (chkbox1, chkbox2), and click on submit, corresponding two text fields (chkbox1,chkbox2) will have to appear in the next jsp i.e., jsp 2.
2. In jsp 1 , i have 3 checkboxes(chkbox1,chkbox2,chkbox3) , if i select check boxes (chkbox2, chkbox3), and click on submit, corresponding two text fields(chkbox2,chkbox3) will have to appear in the next jsp i.e., jsp 2.
Like this, which ever checkbox i select, corresponding text fields should appear in the subsequent jsp.
HashCode And Equals Implementation
May 15, 2014Its that very old question regarding hashcode and equals implementation which i am not getting .
import java.util.*;
public class MyElement {
public static void main(String a[]){
HashSet<Price> lhm = new HashSet<Price>();
lhm.add(new Price("Banana", 20));
lhm.add(new Price("Apple", 40));
[Code] .....
In the above program even if i comment out the Hashcode method , i believe it is still taking the memory address values from the native hashcode method of Object class. but the equals override implentation says that i have two insertions which are same . So as per my logic it should not allow the duplicate element to enter.but its not so ...the duplicate element is well inserted without hashcode .
Grid Layout Implementation
Mar 13, 2014How to implement GridLayout. In my applet, I want to make a grid of 2 rows and 2 columns. In each grid I want to add a Label and a TextField. I want the background to be red.
So my code would be?
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
public class GridLayoutApplet extends Applet implements ActionListener{
// construct components
Label fNameLabel = new Label("First Name");
TextField fNameField = new TextField(20);
[Code] .....
I have read about panels and frames but, it is all confusing to me. How can you add a label and a TextField to one square of the grid?
FFT Convolution Implementation In Java
Dec 26, 2014Not necessarily Java related, more a general programming issue I have come a long and I am currently using java to mock up a project that will eventually get moved over to C++.
I am trying to implement FFT Convolution into a java project and have things partially working, I do not know if it is a coding issue, logic issue or if I simply know nothing of FFT and convolution.
For starters I got an FFT library that I do have working, if I create a small array pass it into the forward FFT, do a little bit of bit manipulation (converting a complex array of size n*2 into a re[] and im[] of size n), run the inverse FFT and do the same bit manipulation again I get back where I started.
However if I take two arrays, a Dirac Delta function (an array with a 1 followed by zeros for the rest of the array) and a stepping kernel (ex. {1, 2, 3, 4 etc}), I would expect to get the forward FFT of both arrays, bit manipulation, multiply them together, Inverse FFT, and bit manipulate again and the result would be the kernel. I have not had such luck.
This is the gist of the program:
// bit manipulation, converts complex array to two re and im arrays
public void bitTwiddle(double [] real, double [] real2, double [] imaginary){
double [] realCopy = new double [] {0, 0, 0, 0, 0, 0, 0, 0};
double [] imaginaryCopy = new double [] {0, 0, 0, 0, 0, 0, 0, 0};
for (int idx = 0; idx < (N * 2); idx++){
realCopy[idx] = real [idx];
[Code] ....
This is the result:
Quote
=====================================================================
Dirac Delta In Time Domain:
Real:1.000.000.000.00
Imag:0.000.000.000.00
=====================================================================
Dirac Delta Frequency Domain
Real:0.500.500.500.50
Imag:0.000.000.000.00
=====================================================================
Kernel In Time Domain
Real:1.002.003.004.00
Imag:0.000.000.000.00
=====================================================================
Kernel In Frequency Domain
Real:5.00-1.00-1.00-1.00
Imag:0.00-1.000.001.00
=====================================================================
Result: Dirac Delta x Kernel
Real:2.50-0.50-0.50-0.50
Imag:0.00-0.000.000.00
=====================================================================
Result In Time Domain
Real:0.501.501.501.50
Imag:0.000.000.00-0.00
Comparator Interface Implementation?
Mar 6, 2014Something about implementing Comparator interface isn't very clear to me: overriding the compare method.
Like here for example:
//This sorts a list of objects holding information based on age: the name and the age of the person
public class Person {
String name;
int age;
public Person (String name, int age)
{
this.name = name;
this.age = age;
[Code] ....
What exactly is happening behind the scenes? I don't understand mostly the part where it returns a 0, a 1, or a -1. After it returns one of those values, what really happens next?
For the displaying of the list, is the method toString() being accessed to output the list in the System.out.println statement?
For the generics, why do we use Person?
Why Class Implementation Is Not Possible In Java
May 14, 2014Why Class implementation is not possible in java....
View Replies View RelatedAbstract Method With No Implementation
Mar 6, 2014An abstract method is a method with no implementation. So would like to know what is the purpose of calling it if there is no implementation?
View Replies View RelatedImplementation Of Immutable Queue
Nov 12, 2014The 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;
[Code] ....
Decision Table Implementation In Java?
Jan 8, 2015how to start with decision table implementation in java
View Replies View RelatedPriority Queue Implementation Using Heap / BST
Dec 4, 2014I 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?)
Implementation Of Login Page With Java
Mar 25, 2014Code for login page by java and how we can implement it.
View Replies View RelatedTo Obtain Explanation On Singleton Implementation
Jan 11, 2014I've found following code for Singleton Implementation from this forum, I am having a difficulty of understanding following,
1. When Singleton instance will be created, ( From which call ) ?
2. What feature of Static Inner class allow object to be singleton ?
3. How Inner Class implementation is thread safe ?
4. What will happen if variable "instance" mark as non-static, Will it still grantee singleton implementation ?
Java Code:
public class Singleton {
// Note private constructor
private Singleton() {}
private static class SingletonInner {
private final static Singleton instance = new Singleton();
}
public static Singleton getInstance() {
return SingletonInner.instance;
}
} mh_sh_highlight_all('java');
File Transfer Protocol Implementation
Mar 19, 2013I have to write a code for File Transfer Protocol! It says that I only need to write code for client, but it also says that I have to run the program and send some files to server. I guess than I also need server side as well. I have to write my own classes, I cannot import some existing classes. I have to connect to the server with password and username and after that send some files to the server. I don't know anything about FTP. Can i maybe do this by Sockets and ports? I worked something with that.
View Replies View RelatedImplementation Of Stack Methods In Java
Jun 3, 2014I have to implement all the stack methods in java such as push, pop empty, not using the ready methods but have to create them and to execute an exercise but is sth wrong with it
public class Stiva {
/** the problem is here how to declare the stack 1 and stack 2 and kreu(head) gjmax(size)*/
int Gjmax;
int array[] = new int[Gjmax];
int kreu;
private Stiva stiva1;
private Stiva stiva2;
[Code] .....
FIFO - Implementation Of Immutable Queue
Nov 12, 2014The 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;
[Code] ......
Implementation Of All Stack Methods In Java
Jun 3, 2014I have to implement all the stack methods in java such as push, pop empty, not using the ready methods but have to create them and to execute an exercise but something wrong with it....
public class Stiva {
/** the problem is here how to declare the stack 1 and stack 2 and kreu(head) gjmax(size)*/
int Gjmax;
int array[] = new int[Gjmax];
int kreu;
private Stiva stiva1;
private Stiva stiva2;
[Code] .....
Quicksort Implementation With Median Pivot
May 19, 2014I am currently writing the Quick Sort implementation where the pivot is chosen to be the medianOf3 element in the sub array. The program should output the total number of comparisons (excluding the ones needed to compute the median itself).I cannot spot any mistake anywhere - yet I am getting the wrong output in the end.
Input file (100.txt) attached.
Current output: 513. Correct output: 518. Where are the missing 5 comparisons? />
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
[code]....
Divide And Conquer Algorithm Implementation
Oct 18, 2014I was given an algorithm to implement and i did it in java. its some divide and conquer algorithm probably some comparison sort..heres the code i wrote...
import java.util.*;//so as to get the functions for using arrays
public class main
{
public static void main(String[] args)
{
int m[]={10,2,3,4,5,6,7,8,9,1};
int result[]=new int[200];
[Code] ....
the program compiles without errors. but while running i get the following errors:
java.lang.ArrayIndexOutOfBoundsException: 10
at main.abc(main.java:28)
at main.main(main.java:8)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)
Running Threads Without Using Runnable Implementation?
Dec 16, 2014I've seen examples that don't use a separate Runnable Implementation, but Instead Just make a subclass of Thread and override the Thread's runO method. That way,you call the Thread's no--arg constructor when you make the new thread;
Thread t = new Thread(); 1/no Runnable"
Any simple code that demonstrates the same. I haven't fully understood what is said in the text above. I have a hunch that the last line is wrong and it should be Thread t = new <Whatever class extends Thread class and over rides its run method>()
Am I correct or wrong....
Servlets :: Website Will Be Down For Maintenance Implementation
Jan 24, 2015So we need to inform all active users of the website that "Website will be down after so and so time for maintenance". This is how I see the implementation.
User can be in any part of the application. So any time user request comes to server, it goes through the controllers. I can write a method (and call from each controller) that checks if message needs to be displayed. Put that into application context and display it. Along with that I will also have a flag that keeps track that if the message has already been displayed or not (to the user). If message has been displayed, no need to call that method again.