What Does Creating ArrayList Object In A Constructor Mean

Mar 22, 2014

import java.util.ArrayList;
public class LectureRoom{
private String courseName;
private String roomNumber;
private String Lecturer;
private ArrayList <Student> studentList;

[Code] .....

Question:

Given the following BlueJ class diagram

Lecturer class (same with previous lab, no changes needed)
Student class (same with previous lab, no changes needed)

LectureRoom (changes occurs here)

1. LectureRoom has roomNumber (e.g. A301), courseName (e.g. Java), lecturer (a reference to a Lecturer object), and studentList (a reference to an ArrayList that stores Student object).
2. LectureRoom has a constructor that receives courseName, roomNumber, and Lecturer. The constructor then sets/assign the courseName, roomNumber and Lecturer. This constructor also creates the studentList arraylist object.

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Super Constructor Call - Creating Object

Sep 18, 2014

Its written that every constructor calls its super class constructor. And we know, constructors are called to create an object. Does it mean that if I am creating an object of a class, I am actually creating objects of all its super class???

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Populating ArrayList Object With Nested ArrayList Object

Jul 8, 2014

I have stumbled onto a problem with ArrayLists (not sure if nested ArrayList objects would be a more accurate description) ....

As simply put as I can describe it, I have an Inventory class which creates an ArrayList of a Product superclass, which has two subclasses, PerishableProduct and ItemisedProduct.

By default, the program is meant to have a starting inventory, which is why I have added them in the constructor

public class Inventory {
private List<Product> products;
public Inventory() {
addProduct(new Product("Frying pan", 15, 20));
addProduct(new PerishableProduct("Apple", 5.8, 30, 7));
addProduct(new ItemisedProduct("Cereal", 5.8, 0));
// this is where I am having problems. Wanting to add
// objects to the ItemisedProduct's ArrayList for cereal.
}

Within the ItemisedProduct subclass is yet another ArrayList which is meant to hold serial numbers.

public class ItemisedProduct extends Product {
private ArrayList<String> serialNumbers = new ArrayList();
public ItemisedProduct(String name, double price, int qty) {
super(name, price, qty)

[Code] .....

My problem is that I do not know how to populate the serialNumbers ArrayList from the Inventory class' constructor. Because technically, quantity is defined by how many serial numbers are created.

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ArrayList In No Arguments Constructor

Sep 29, 2014

I have been able to create a no arg constructor and pass empty double, int, and strings but i am not able to pass an arraylist.

class Savings {
private double balance;
private ArrayList <String> transaction = new ArrayList();
public Savings (double B)/>
{
balance = b;
}
public Savings()
{
this(0.0,new ArrayList());
}

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Why Isn't Constructor A Requirement For Creating Objects

Jun 13, 2014

Java Code:

class GenericQueue<E> {
private LinkedList<E> list = new LinkedList<E>();
public void push(E element) {
list.addFirst(element);
}
public E pull() {
return list.removeLast();

[code]...

Is a constructor required to create an object, if one of its instance or class variables haven't been instantiated? Like private String string;

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Mar 16, 2014

I want to create a simple app that takes a name from the console then compares the name to a small phone book,when the name matches another name it will return the associated phone number.

I have a small contacts class which has name and number fields,Then I have a phone book class which populates an array with 4 contact objects that I can compare the entered number against.

here is my contacts class

public class Contact
{
String name;
int number;

[Code].....

In the main method I am just trying to print out one of the fields for one contact to see if I can actually access it to compare it to the name entered.Its saying "MaryJones" cannot be resolved to a type.I'm guessing I cant create all that code in the constructor?

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Jul 14, 2014

I thought you can only create a new object using private implementations and then using a constructor to set your arguments inside the parameters of the constructor to the instance variables but how come he created an object without any private implementations and just methods inside the constructor.

import javax.swing.JFrame;
public class MyWindow extends JFrame {
public static void main(String[]args){
new MyWindow();
}
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setSize(500,500);
setVisible(true);
setTitle("MyWindow");
}
}

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LightController And Circle Class - Creating A Constructor

Jan 6, 2015

I have two classes LightController & Circle. I need to use the LightController class to do the following:

Creates an instance of Circle with a diameter of 50 and a colour of OUColour.GREEN and assigns this new circle to the instance variable light.

Sets the xPos of light to 122.
Sets the yPos of light to 162.

I am struggling to write the correct line of code to set the colour to green and set diameter to 50.

Code for the two classes below.

001
import ou.*;
002
import java.util.*;
003
/**
004
* Class LightController
005
* This class uses the Circle class, and the Shapes window

[Code] ......

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Creating WordCounter Class With A Constructor That Takes File Name As Parameter

Mar 4, 2014

Instructions

Create a WordCounter class with a constructor that takes a file name as a parameter

The class should have two fields: one for the file name and one for a HashMap to store word count information

The constructor should call a private method, countWords, that reads in the file and counts the word frequencies

The class should contain a get method for each field, as well as a print method that prints out the map in the following format:word:frequency

When printing, the map should be sorted by either the word order or frequency (Hint: see Collections.sort)

You should include the sample text file on Blackboard. This is what i got so far

Java Code:

import java.io.File;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Scanner;
public class WordCounter

[Code] ....

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Why Put Other Objects In Object Constructor

Jun 6, 2014

When using Java Code:

Scanner scan = new Scanner(system.in) mh_sh_highlight_all('java');

Why do we put System.in in the constructor? What purpose does it serve and why can't we just not use it?

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Tracking Constructor To See If It Recreate Object

Aug 2, 2014

that i started to learn programming and i started with java. so there is a book that i'm on it right now called "Pearson Absolute Java 5th Edition" by Walter Savitch anyway i'm on a project in fifth season which i have to create a class named HotDogStand that operates several hotdog stands distributed throughout town. the whole program is clear. although its so easy to accomplish , my question is more about debugging. so here is the code:

public class HotDogStand
{
private int id; //id number of hotdog stand
private int hotDogsPerDay; //hotdogs sold by one stand
private static int totalHotDogs; //the static value for total hotdogs sold by all the stands
public HotDogStand (int newID, int hotDogsPerDay) {
this.id = newID;
this.hotDogsPerDay = hotDogsPerDay;
totalHotDogs += hotDogsPerDay; //to add the value every time the user uses the constructor (every time the user creates an object)

[code]....

everything works fine. but my question is what if someone use a constructor again? you see if in the main method someone do this after creating the object "stand3":

HotDogStand stand3 = new HotDogStand(3, 43);
stand3 = new HotDogStand(3,40);

i know that it's logical to use setter method but this program doesn't have one. if someone do the thing i wrote above, the calculation of static variable, totalHotDogs will be all wrong. because of totalHotDogs += hotDogsPerDay; it will add another value for the same object. how can i tell the machine to ignore the second (or more) invocation of the constructor for the same object?

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How To Have Unlimited Object Parameters In Constructor

Nov 21, 2014

I want to create an order system. My Problem is that I want to create it dynamic, with ArrayLists and no fixed Array size.

Basically I have already a User which is able to purchase something.

User a = new User();
Car car = new Car("blue",500);
a.purchase(new Order(new OrderThing(5,car));

This will work!

But I want something like this:

a.purchase(new Order(new orderThing(5,car), new orderThing(2,car), new OrderThing(1,car),...)

Basically I don't know how much OrderThings I want to create before I type in the OrderThings with new Order().

But in java it is before you can construct orderThings you must already know in the constructer how much objects you do want.

Now as im writing this question I got a idea of waiting for an Array of new OrderThing but it don't work. When I write

a.purchase(new Order(new orderThing(5,car), new orderThing(2,car)))

it wants a constructor which is based on Order(orderThing,orderThing)

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Jan 21, 2015

I'm writing a program that acts as a 'pocket' where the user is able to enter a kind of coin, such as, a quarter and the amount of quarters it has. I was assigned to do 3 different class, the Coin Class in which the coins and their values can be instatiated from, a Pocket Class, where I have to write a method that can add the coins of the user (basically the method would act like ArrayList .add() ) and the PocketClass tester. I have already written most of the code, but I am stuck as to how I could write the following method:

Java Code:

public void addCoin(String s, int i) {
// s is type of coin, you are using s to instantiate a Coin and get value
// i is number of coins, you are using i to keep adding value to the totalValuefor
} mh_sh_highlight_all('java');

Would I use a for-loop in order to keep track of the number of coins? I would use ArrayList but the assignment calls for creating a method similar to that of .add()

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Feb 11, 2015

So I want to write a constructor that creates a new object with the data from the array values. I don't know where to start. It's the last method in the code:

public class Measurements {
private double[] values;
private double[] newArray;
private int n; //numberofvalues
private double[] ms;
public Measurements(int max) { //constructor

[code]....

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How To Create Object To Be Null If Class Constructor Parameter Is Int

Mar 8, 2015

I have a class of Date with a constructor with 3 parameters in it. Those 3 parameters are int data type just to enter month, year, day.

I have another class called Author which has a constructor of Date diedDate; as a parameter passing to the Author constructor.

I was asked to call the Date parameter is null, call the default constructor but I thought for the Date parameter I could only enter something like 0,0,0 instead of typing in null, null, null because null is for String data type isn't it?

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Create A New Instance Carte Of Object Carti Using Constructor

Mar 30, 2014

what have I done wrong n the following code? I'm trying to create a new instance carte of object Carti using the constructor and then to insert a row into a table created with SQL.The error I'm getting is:

Exception in thread "main" java.lang.NullPointerException
at Carti.Carti.InsertCarti(Carti.java:103)
at Main.main(Main.java:37)
Java Result: 1
BUILD SUCCESSFUL (total time: 28 seconds)

The line Main.main(Main.java:37) is when I try to insert the row.
The line Carti.Carti.InsertCarti(Carti.java:103) is when I do the
PreparedStatement st = conn.prepareStatement("insert into Carti (Id,titlu"
+ ", descriere, autor, editie, anPublicare) values (?,?,?,?,?,?)");

Here is the code (Main and Carti Classes)

import Carti.Carti;
import Imprumut_Carti.Imprumut_Carti;
import Membrii.Membrii;
import static com.sun.org.apache.xalan.internal.lib.ExsltDatetime.date;
import static com.sun.org.apache.xalan.internal.lib.ExsltDatetime.date;
import java.sql.SQLException;
import java.text.DateFormat;
 
[code]....

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Creating ArrayList And Adding Item To Array

Nov 27, 2014

Creating an Arraylist and adding item to that array, refer below code

ArrayList<String> sjarr = new ArrayList<String>();

Statement1:
String arritem1 = new String("First array item");
sjarr.add(arritem1);

Statement2:
String num = "text will decide";
sjarr.add(num);

Both adds the String item to array list but puzzling what makes the difference....

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Apr 7, 2015

I'm creating a card game assignment... so i have an arraylist called cards that has 20 cards and every card has contains 2 objects, suit and the point Value.

I shuffled the deck, now i want to add half of it to player 1 and the rest of the cards goes to the bot or computer.

how can i add the cards to the player one arraylist and have all the information of the cards?

here is my Deck class code :-

public class Deck {
private ArrayList cards;
private int size;
private ArrayList player1;
private ArrayList bot;

[code]....

the problem i have is this one doesn't work

size = cards.size() / 2;
for (int i = 0; i < size - 1; i++) {
player1.add(cards.get(i));
}
for (int s = size; s < cards.size() - 1; s++) {
bot.add(cards.get(s));
}

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Feb 7, 2014

I've a parent class with a argument constructor like below(a sample code)

public class Parent {
Parent(String name) {
System.out.println(name);
}
public static void main(String[] args) {
}
}

Also I've child.class which extends Parent.class as shown below,

public class child extends Parent {
child(String name) {
super(name);
}
}

Now, I want create/modify the constructor which is in child, by taking "int i" as an input instead of "String name". How can I do that? Run time I want to execute child constructor not a parent constructor.

Condition is: Without making any changes to the Parent class

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Jun 9, 2014

I'm really new to object oriented coding. A good way to create a Text Based Game that used objects as rooms, and items. However, I can't figure out what the best way to define and use rooms and items would be. I've been at it for the past few days, and just can't think of something that works well and is easy to use.

I want to have each room have it's own "inventory" of items that the player can pickup, as well as drop items into. I want items that are dropped to maintain their properties (durability, level, ect). I would also need several methods for things like getting an item from a room by the item's display name or id. For instance, if there is a room with a Broken Iron Sword, and a Stone Dagger, I'd need to be able to get the Broken Iron Sword object with the string "Broken Iron Sword".

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Jan 30, 2015

So I'm Half way done with this assignment and all I need to is edit and sort my directory. What I've been trying to do as of now is edit my directory. I've tried to use the set function in the Array List, Iterator List etc but I just don't know how implement them mainly because I keep thinking "how can check which variable in the directory the user wants to change(Name, cost etc etc)?".

Main class

Java Code:

package plantnursery;
import java.util.Scanner;
import java.util.ArrayList;
public class PlantNursery {
private ArrayList<Plant> plantDirectory = new ArrayList<>();
private static Scanner read = new Scanner(System.in);

[Code] .....

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Aug 23, 2014

package home;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Box{
int x=70;
int y=70;

[Code] ....

L a = new L(); causing the error. It will be great to know why it is showing error.

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Mar 6, 2014

I just want to ask about a kind inheritance.Let say I have an interface MachineCode.I also have different classes, Binary, Hex and Octal that implements MachineCode

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Binary bin = new Binary();
Hex hex = new Hex();
Octal octal = new Octal();

those declaration above must be compile error,

I want to create Objects of Binary, Hex, and Octal this way:
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MachineCode hex = new Hex();
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Nov 7, 2014

i have a class that creates an object made of 2 strings and an arraylist

class Users{
private String ip;
private String userName;
private ArrayList <String>cons=new ArrayList();
Users(String i_p,String un,ArrayList con){//construc

[Code] .....

This object then gets returned to an arraylist of these objects

static ArrayList<Users>users=new ArrayList();

My question is how can i then get the arraylist from this object to print its contents?

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Oct 12, 2014

I have got the code listed below:

class Address {
String name;
String street;
String city;
String state;
String code;
  Address (String n,String s, String c, String st, String cd){

[code]....

Using JDK7 is there a way to get an object that has got a specific property from the collection? For instance, I might want to seek if there is an Address containg "Tim Carlton" in the ArrayList.

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Oct 7, 2014

I'm almost finished my Bank Account exercise and I found myself stuck at the last part. Its asking me to add a method that asks the user to input the name of the account into which they want to deposit money, then search the ArrayList for that account. If it is found, the user is asked how much money they wish to deposit.

I already have my deposit method sorted so basically what I need is just searching through the ArrayList by the name variable. I assume its don't by iterating through with some form of for loop.Heres what I have:

import java.util.Scanner;
public class BankAccount {
private double balance;
private String name;
public BankAccount(double balance, String name){
this.balance = balance;

[Code]......

And the driver class

import java.util.ArrayList;
import java.util.Scanner;
public class BankDriver {
Scanner scan = new Scanner(System.in);
ArrayList<BankAccount> list;
public BankDriver(){

[Code]...

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