Method That Return Instance Of A Class That Implement Iterator Interface

Apr 14, 2015

I 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] ...

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Cannot Return Object Of Iterator As Its An Interface

Mar 3, 2014

What does the iterator() method return???it can't return an object of Iterator as it's an interface...

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Sep 17, 2014

So I created an interface which has the method

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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?

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Mar 7, 2015

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Java Code:

if(x instance of y){ //where x and y are both interface objects
doSomething();
} mh_sh_highlight_all('java');

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Sep 3, 2014

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Apr 12, 2014

how to 'implement' an interface and 'extend' a class. Now I want to try and recall the information by memory without using any reference material.
Implementing an interface...

Java Code: //This interface will hold information for cell phones//Like saying... you can't BE a cell phone unless you have this information, at the very least

public interface CellInfo {
public void model();
public void make();
public void androidVer();

}

//Now I implement the interface for a class called Galaxy, which is a class about a specific phone

public class Galaxy implements CellInfo
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}

public void make() {
System.out.println("I'm made by Samsung.");

[code]....

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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

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Widget Class That Implement Comparable Interface

Mar 15, 2014

Below is the requirements and code. I am getting the error CODELAB ANALYSIS: LOGICAL ERROR(S)We think you might want to consider using: >

Hints:

-Correct solutions that use equals almost certainly also uses high
-Correct solutions that use equals almost certainly also uses low

Assume the existence of a Widget class that implements the Comparable interface and thus has a compareTo method that accepts an Object parameter and returns an int . Write an efficient static method , getWidgetMatch, that has two parameters . The first parameter is a reference to a Widget object . The second parameter is a potentially very large array of Widget objects that has been sorted in ascending order based on the Widget compareTo method . The getWidgetMatch searches for an element in the array that matches the first parameter on the basis of the equals method and returns true if found and false otherwise.

public static boolean getWidgetMatch(Widget a, Widget[] b){
int bot=0;
int top=b.length-1;
int x = 0;
int y=0;
while (bot >= top)

[code]....

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Dec 2, 2014

Let'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.

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Jan 23, 2015

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Dec 15, 2014

How do you enforce any class which implements an interface should also implement comparable too? Say for instance you may have an interface

public interface Task
{ ... }
public class DoThis implements Task { ... }
public class DoThis1 implements Task { ... }

I want all of the classes which implements the interface Task to implement comparable too. Of course I can just say implements Task, Comparable. But is there something which we could do from interface level, i mean interface Task level?

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How To Write Instance Method For Rectangle Class Called Contains

May 29, 2014

Write an instance method, contains, that has one explicit parameter of type Rectangle. The method should return true if every point of the rectangle determined by the explicit parameter is on or within the rectangle determined by the implicit parameter. It should return false otherwise.

This is what i did so far?

public boolean contains(Rectangle other) {
Rectangle intersect = Rectangle.intersection(this, other);
if ((intersect.left == this.left) && (intersect.bottom == this.bottom) && (intersect.width == this.width)
&& (intersect.height == this.height)) {
return true;
} else {
return false;
}
}

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Mar 12, 2015

How do I create an instance of a class in a method?

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I have a abstract class, School, and inside School I have some methods that must preform some action on an instance. For example, there is a move() method that must move the instance of School. Another method named, personOld(), which returns whether or not an instance of School surpassed some determined age.

How do I do this and create this instance?

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Jan 16, 2015

I 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]....

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Oct 27, 2014

This 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] ......

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May 5, 2014

I'm just wondering why variables in interface can't be instance scope?

interface Test{
int a;
}

And then

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Yes, it violates OO, but I don't see why this is not possible? Since interface is not an implementation, therefore it can;t have any instance scope variable. I can't find the correlation of interface being abstract and being able to hold instance scope variable. There's gotta be another reason. I'm just curious about any programmatic limitation, not deliberate design constraint. the example of programmatic limitation is like when Java forbids multiple inheritance since when different parents have the exact same method, then the child will have trouble determining which method to run at runtime.

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Sep 7, 2014

I want to use a method, which takes for example an int and also returns an integer. For example, if the the given integer is strong return a, if it is notstrong return b. How would you write that in a Code?

I want to use that in a more general way. I want to give a method mlong the value X of the type date and let it return an int. Type date consists of 3 int, one of them is the int month.

mlong should return an int depending on the X.moth. at the moment my code looks like this:

// File1:
public class date {
public int day;
public int month;
public int year;
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// File 2:
public class monthlength {
public int mlong(date X) {
int t;
t = X.month;
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Nov 16, 2014

I need to implement the attached interface ("Locality"). In the attached UML diagram it has a 1 on 1 relationship with the class "Team". I don't know if this can be somehow implemented in Java. Can I create the attribute "team" in the Locality interface and let it be used by the "Town" and "City" classes? Could it be better to implement it as an abstract class instead?

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Feb 24, 2014

The Iteratior provides the functionality of traversing and removal which we can achieve through normal for loop and remove() of the data structure.Then, why do we need Iterator explicitly and as an inner class?

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Jan 8, 2014

I am writing a game in Java for Android (although my question isn't Android or Game Dev specific).

I have a SceneManager class and a Scene interface and then various other classes that implement the Scene interface (Code at the end of this post).

Basically, in my MainGame class (which also implements the Scene Interface for Touch Event capturing purposes) I hold the bulk of my game code. Methods in this class are then called from my Level classes. (most of these are needed in all levels so it makes sense to hold them here and call them from the levels to eliminate unnecessary code duplication)

So, I have Level1, Level2......... Level20 classes which all implement Scene.

Now, the problem comes because in only 2 of my Levels something can happen (that can't in the other 18) and I need to run a response method in these 2 levels (the method isn't exactly the same, the response to this event happening is different for both levels).

To run common methods from my classes, I use my Scene Manager like this:

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(The above is from my gameloop) - So it will run the updateLogic(); and render(); methods from whichever is the current scene (Level).

Scene is changed like so:

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This works great as all Level's have an updateLogic(); and render(); method.

So from my mainGame class, I am doing something like : (pseudo code)

public void checkIfSomethingHappened(){
if (something happens){
if (currentLevel==5){
Level5.response();}

[Code]....

The above would be called from my 2 level classes. So something like:

MainGame.checkIfSomethingHappened(); //Called in addition to the normal methods that make up that level

I don't really want to have this (second) 'if' statement here in the middle of my performance critical game loop.

What I'm after is something like this:

if (something happens){
SceneManager.getInstance().getCurrentScene().response();
}

However, this would require me to put stubs in the other 18 classes.

I'm thinking there must be a way to do this as the SceneManager already knows the current scene so it seems a waste checking it again via an if (or switch) statement. What is the best way to do this without having to put stubs into classes that don't require this method?

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Apr 2, 2014

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When i create an object in main method and pass values to my function of return type TwoDPoint,it gives error:- found int,int need TwoDPoiint,TwoDPoint.

// Here is what i tried to do:

Created class TwoDPoint that contains two fields x, y which are of type int. Defined another class TestTwoDPoint, where a main method is defined.In the main method created two TwoDPoint objects.

Then I modified the class TestTwoDPoint and add another function to it. This function takes two TwoDPoints as input and returns the TwoDPoint that is farthest from the point (0,0).

Then I added another function to TestTwoDPoint. This function takes two TwoDPoints as input and returns a new TwoDPoint whose x value is the sum of x values of the input TwoDPoint's and whose y value is the sum of the y values of the input TwoDPoint's.

class TwoDPoint {
int x = 2;
int y = 4;
}
class TestTwoDPoint {
public static void main(String args[]) {
TwoDPoint obj1 = new TwoDPoint();
System.out.println(obj1.x);
System.out.println(obj1.y);

[Code] ....

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Jun 15, 2014

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Here's my code so far:

Driver.java
import java.util.Scanner;
import java.io.FileNotFoundException;
import javax.swing.JFileChooser;
import java.io.File;

[Code].....

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Nov 16, 2014

I am a beginner here at JAVA and I am trying to program a Gratuity Calculator using both interface class and object class but it keeps on compiling with errors saying "cannot find symbol".I tried everything to fix it but it just keeps on stating symbol.

[CODE]
public class GratuityCalculator extends JFrame
{
/* declarations */
 
// color objects
Color black = new Color(0, 0, 0);
Color white = new Color(255, 255, 255);
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[code]....

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Oct 30, 2014

Alright, I don't understand how to link my compress method to my return statement method "getPText". Also in my compression I only want it to compress for 3 or more consecutive letters.

import java.util.Scanner;
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[Code]...

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