Which Two Method HashMap Key Object Should Implement
Jul 25, 2014Which two method HashMap key object should implement?..
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Implement HashMap Put And Get Methods Without Using Java Collection Framework?
Feb 11, 2014How to implement HashMap put and get methods without using Java Collection framework?
View Replies View RelatedGetting Object From HashMap
Oct 23, 2014I am trying to retrieve a object from a hashMap not I am not sure what is wrong. I am trying to calculate if a car was speeding. They're 5 cameras and as they pass each camera I can calculate the speed. They key is camera number and I am sending in a Vehicle object.
Now I am trying to retrieve variables from the Vehicle so I can do the calculations. I am getting the error in the loop in void calculateSpeeding(). The loop is only for testing at the moment.
package online.practice.averageSpeed;
import java.util.Arrays;
import java.util.HashMap;
public class Vehicle {
String licensePlates;
[Code] ....
Object Library Hashmap
Jul 16, 2014My perfect idea is to have a Hashmap that would increase size each Key & value added, it's almost like a self-increasing array. I mean I could just create a very large Hashmap for me to add objects to anytime I want with a key to be able to find the object. Is this the most efficient way, because I'm trying to make my Object Library compatible with any amount of Objects, however, I know there's a limit to how many values you can have in an array, but it's larger than I'll ever need.
Let's say I'm making a number storage program, and I may need from 3 to 8 numbers to be stored with a key to find them easily using a Hashmap, rarely I may need below 3 or above 8. So is it efficient for me to create a Hashmap that has 10 placeholders? Or can I make this more efficient. Note, my Library is static.
How To Get Method Of HashMap Or Hashtable
Jul 25, 2014How get method of HashMap or Hashtable works internally in Java can any body let me know how does it work..
View Replies View RelatedClasses Of Object - Implement Two Out Of Three Interfaces
May 8, 2014I have three classes of object, most of which must implement two out of three interfaces. The interfaces look like this:
public interface Source {
public void startSending();
} public interface Sender {
public void setReceiver();
[Code] .....
That works fine, but I am wondering if pairing the interfaces into subinterfaces is a defensible methodology. For example, all classes that act like Producer must implement both the Source and Sender interfaces. And all classes that act like Relayer must implement the Sender and BlackHole interfaces. I could define two subinterfaces like this:
public interface Factory extends Source, Sender {
}
public interface Modifier extends BlackHole, Sender {
}
I could then define my classes like this:
public class Producer implements Factory {
}
public class Relayer implements Modifier {
}
public class Consumer implements BlackHole {
}
Within the class definitions, it makes no difference, as I will have to implement the same methods either way. But it seems more self-documentary to create the subinterfaces from their parent interfaces and name them in ways that reflect what the classes that implement them must actually do.
Implement Method Named ViewAllFactor
Jan 14, 2014so, i have a problem in implement method named viewAllFactor(User us,ResultSet rs)when i call this method using <T> like objet dont work because T obj is nulli ask if i can try something to have a good result.
I have 2 classes BaseDao<T> (DAO Pattern) and Class User extends from BaseDao
this is the code
package appweb.core;
public abstract class BaseDao<T> {
public ArrayList<T> viewall() {
ResultSet rset = null;
ArrayList<T> listAll = new ArrayList<T>();
String sql = "SELECT* FROM "+ this.tableName;
System.out.println(sql);
try {
[code]....
Implement Method Inside Interface
Sep 3, 2014if i call a class that implements an interface the method inside the interface will be triggered automatically by the compiler or happens only in the observer pattern? i keep simple to be surr the message came across, a typical example would be a listener on a button, or a collection that calls comparator)
View Replies View RelatedImplement Add Method For Singly Linked List
Apr 26, 2015Implementing the add(int i, E o) method for a SinglyLinked List.
public void add(int i, E o)
// pre: 0<=i<= size()
// post: adds ith entry of list to o
Implement Hash Of Hashes As Method Parameter
Apr 28, 2015I have a drop-down which contains the four sections simple buttons(filters). When click any of these buttons some settings are applied. I have successfully auotmated it using simple if else and switch but in that case i have to use 8 parameters(8 are the number of button)
public void editFilters(WebElement filter1, WebElement filter2, WebElement filter3, WebElement filter4,WebElement filter5,WebElement filter6,WebElement filter7,WebElement filter8 String edit, String expectedColour) {
switch (edit) {
case "selectFilter":
if (filter1 != null) {
[Code] .....
But want to make it more effective by using hashes. I do not want to use 8 different parameters to perform action on the respective button.
So now what i want to implement.
Create a method in which i pass the parameter1 as hash and 2nd parameter as 0 or 1, 0 means unSelectFilter and 1 means select the filter.
With parameter 1, in code i want to pass the name or xpath or anything else for any number of filters , that those filters names should be stored into that hash and then by passing 0 or 1, i can select/unselect those filters.
Call Method In All Objects Which Implement Certain Interface
Apr 15, 2015 if some of you worked with Unity Game engine (C#) the idea is that game has main loop and once per cycle it call for example Update() method in all objects which implement certain interface.
I would like to repeat such pattern in Java for another another program, not even game related, but I would still need a main loop and event driven behaviour with async call backsSo question is how to implement the fallowing scenario:
Imagine i have interface which implement some methods and one of them is Execute()
I have the main controller class which implement main loop, also multiple other classes which implement the same interface with method Execute(). How can i call this Execute() method on all objects which implement that interface each loop cycle?
Should i keep and track reference of each object which was implemented with this interface and go through inner "for" loop trough each reference and call manually Execute() method in each of them?what if each object implementing interface have to run Execute() method simultaneously? in parallel independent from each other?
Referring back to Unity engine and their Update() method - there is exactly the same situation:you can have multiple objects with script attached, thats script implement interface which has multiple methods and one of them is Update() and once per cycle all objects with that Update() method will be executed in parallel independently
Java Interface - Implement Method In Another Class
Sep 17, 2014So I created an interface which has the method
int getCalls();
I am trying to implement this method in another class but I'm not sure how to do so. My attempt is:
public getCalls(){ return getCalls(); }
When I run the program it sends the following exception:
Exception in thread "main" java.lang.StackOverflowError
at FibonacciForget.getCalls(FibonacciForget.java:14)
and it highlights the [return getCalls();] part.
What is the correct way to implement the getCalls() method?
Equals Method - Take Object Reference And Return True If Given Object Equals This Object
Mar 28, 2014Create an equals method that takes an object reference and returns true if the given object equals this object.
Hint: You'll need 'instanceof' and cast to a (Geocache)
So far I have:
public boolean equals(Object O){
if(O instanceof Geocache){
Geocache j=(Geocache) O;
if (this.equals(j)) //I know this is wrong... but I can't figure it out
return true;
}
else return false;
}
I think I have it correct up to the casting but I don't understand what I'm suppose to do with the this.equals(). Also I'm getting an error that I'm not returning a boolean... I get this all the time in other problems. I don't get why since I have to instances of returning booleans in this. "returns true if the given object equals this object" makes no sense to me. I assume the given object, in my case, is 'O'. What is 'this' object referring to?
Trying To Implement Interface - The Method DoSomething Is Undefined For The Type B
Dec 2, 2014Let's say we have situation like this:
abstract class A
class B extends A
class C extends B
class D extends C implements SomeInterface
I'm trying to implement a method "doSomething" declared in SomeInterface in class D. While trying to call doSomething in main I get the error message ”The method doSomething is undefined for the type B”
This is my code i main:
B container = new D("1,2,3,4,5,6,7,8");
System.out.println(container.doSomething());
I need container to be an object of type B, because it goes later into a list of type B. According to what I've been told, the only file I need to edit to make this work is class D.
Servlets :: How To Implement A Callback Method For A Post Async Task
Mar 26, 2015I am developing an app with a Java Servlet backend, and I am trying to get the Async call (AsyncTask - Android Developers) to get my response message Synced with the rest of the client and being able use this information wherever I want. Without a callback method, when from the caller class I use the commands:
ServletPostAsyncTask s = new ServletPostAsyncTask();
s.execute(new Pair<Context, String>(ListViewPrenota.this, "tours"));
Tours ttours = s.tours;
Tour tour = ttours.getTours().get(0);
I receive a NullPointerException pointing to the third line Tours ttours = s.tours;, since the s.execute() method doesn't wait for the rest of the lines to get executed.To solve this I thought about implementing a callback method with interfaces in Java, but I am not sure on how to do it. For example, what class does have to implement the interface, the ServletPostAsyncTask or the caller class?
Program That Implement Final Method And Perform Arithmetic Operation
Mar 4, 2014class A
{
public final int Add(int a,int b) {
return a+b;
}
}
class B
{
public static void main (String args[])
{
System.out.println(Model.Add(5,10));
}
}
This is what I have. I'm not sure if this even makes use of a final method. But when I run it I get an error saying cannot find symbol for line 13.
Swing/AWT/SWT :: SetLayout Does Not Override Or Implement Method From Super Type?
Sep 12, 2014I am trying to make a ChessBoard class composed of an array of JLabels inside a JPanel with a grid layout. I am also trying to override the getPreferredSize method so that the board will change size when I resize the main window (in another class in which I will instancize this class as part of a larger GUI). I got this kind of layout working before, but now I am trying to get it to work with multiple classes. However, after copying in the part of the previous code corresponding to the panel's layout, I am encountering some errors that I don't know how to solve. Specifically, when I try to override the getPreferredSize method, the compiler tells me "method does not override or implement a method from a super type, " and that it can't find the method "getPreferredSize"
Here's my code:
public class ChessBoard extends JPanel//the panel that this class extends is the boardHousing
{
//mental chess board piece array
Piece mentalBoard[][] = new Piece[8][8];
//actual GUI chessboard JLabel Array
static JLabel chessBoard[][] = new JLabel[8][8];
[Code] ....
I would just think that I was overriding the method incorrectly, but the weird thing is that I got that specific section of code to work before -- the only thing different now is that there are multiple classes, so my ChessBoard class itself is extending JPanel.
Method That Return Instance Of A Class That Implement Iterator Interface
Apr 14, 2015I have been researching the Iterator and making a class implement iterable. I have seen this example shown below and was wondering how I could change this so that iterable() is not called upon in the main. I would like to be able to make a method that returns an instance of a class that implements the Iterator interface hopefully an inner class. This is because my program will not have a main and will be supplied with a main that includes a new Object with will use the iterator method.
import java.util.*;
public class IteratorDemo {
public static void main(String args[]) {
// Create an array list
ArrayList al = new ArrayList();
// add elements to the array list
al.add("C");
[Code] ....
This is all I have been able to understand from what I want to do. This does not work and this is what I am trying to achieve
public class MyArrayList implements Iterable {
public static final int DEFAULT_SIZE = 5;
public static final int EXPANSION = 5;
private int capacity;
private int size;
private Object[] items;
[Code] ...
How To Implement Collections Binary Search Method On ArrayList Of Custom Objects
May 11, 2012I'm doubted regarding the implementation of Collections.binarySearch() method on an ArrayList of objects of a custom class Movie.
Here is the movie class :
public class Movie implements Comparable<Movie> {
String movieName;
String rating;
String director;
String theme;
[Code] .....
The sort/binarySearch in searchByMovieName function is done with natural sorting (and Comparable Interface in Movie class). I mean no comparators involved here. And the comparator that I used for sorting/binarySearching on Movies Director attribute in searchByMovieDirector function is :
public class MovieDirectorComparator implements Comparator<Movie> {
public int compare(Movie movie1, Movie movie2) {
return movie1.getDirector().compareToIgnoreCase(movie2.getDirector());
}
}
But I was not able to implement binarySearch ?? How to implement the binarySearch here. I have google to see only binarySearch working on Arrays or probably ArrayList of String only, but not on ArrayList of custom objects.
Implement Equality And HashCode Method If Class Has Reference Type Members?
Jan 16, 2015I am trying to implement the following example to override the equality and hashCode method if the class has reference type member. I do get the expected result "true" for equal and "false" for non-equal objects. But the print statement in the Circle's equal method is not executed when the objects values are not equal. I don't know what i am missing, though i get the equality result "false" as expected for non equal objects.
class Point{
private int x, y;
Point (int x, int y) {
this.x =x;
this.y = y;
[code]....
Swing/AWT/SWT :: Error At Class Name - Type JTextField Must Implement Inherited Abstract Method
Oct 27, 2014This code is directly from Swing: I'm using Eclipse and keep getting an error on line 10 saying :
"The type JTextField must implement the inherited abstract method ActionListener.actionPerformed(ActionEvent)."
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
[Code] ......
Unable To Implement Custom Request Method In HTTP Header While Posting Data To Server URL
Jun 26, 2015I have been trying to implement custom request method in HTTP header while posting my data to the server URL. My application specific URL accepts -X parameter and -d for the data and it is mandatory for that url. Basically I am trying to dump JSON data into my influx DB using CURL command which is working fine from the shell. But the issue is, if I am implementing the same in java with proper approach, it is not supported or working. My CURL command is :
curl -X POST -d '<my_json_data>' '<my_url>'
How can I implement the same in java using HttpUrlConnection or other available approach?
Which Method Is Used While Passing Or Returning A Object From The Native Method
Mar 5, 2014Which method is used while passing or returning a java object from the native method?
View Replies View RelatedCalling Object Method From Another Object
Oct 26, 2014I've been trying to learn Java for the last 36 hours or so (after applying for a HTML/CSS job saying "Java knowledge preferred"), and decided to experiment a bit making a graphical tic-tac-toe game. I eventually managed to get that done and it's working. Working code below:
[Java] tic tac toe 1 - Pastebin
So, it works to an extent, however, the way I am capturing which cell is selected seems very sloppy, and would not work if the cells weren't squares or rectangles. So I made a copy of the project and restructured it adding the mouse event to the cells, but now I can't get JComponent to repaint. New code below:
tic tac toe 2 - Pastebin
Curiously, clicking triggers the action for all 9 cells, but I presume it's because I haven't bounded them making it think I've clicked all 9 simultaneously.
What I've tried:
Make the Cell class extend the game class and call this.repaint()- causes stack overflow.
Calling Game.GameState() within the cell clicking event and making that function static - compiler doesn't like calling repaint() inside a static function.
Making another class to make a clone of the Game object and then refresh- was never going to work....
Object Method Override
Mar 7, 2014I read the following comment at stackoverflow.com. It is not clear to me why equals in the code below does not override - i looked up Object class equals() and the signature is same.
public class Foo {
private String id;
public boolean equals(Foo f) { return id.equals(f.id);}
}
This class compiles as written, but adding the @Override tag to the equals method will cause a compilation error as it does not override the equals method on Object.
Cannot Convert From Object To E In Last Line Of Pop Method
Jul 20, 2014I am getting this error "Type mismatch: cannot convert from Object to E" in the last line of the pop() method.
package stack;
public class Node<E> {
E item;
Node next;
Node(E item) {
this.item = item;
this.next = null;
}
[code]....
I don't understand why that error occurs despite item being declared as type E in the Node class.