I am trying to read a file into an array list, change some things about it, and then write it to another file. Files are getting written with what was read repeating a second time. I've tested the read method by having it print everything which goes into the ArrayList object. I then did the same with the write method which seems to write everything twice, as if everything is in the ArrayList twice, but I'm not sure how this is possible, since the read clearly did everything only once. Perhaps the ArrayList isn't the best collection to use for this purpose.
The read method:
Java Code:
private ArrayList<String> read(File in) {
String line;
ArrayList<String> data = new ArrayList<String>();
try {
BufferedReader r = new BufferedReader(new FileReader(in));
I'm attempting to make a simple Pythagorean Theorem program (A squared + B squared = C squared) but am running into problems when I write it as object oriented. The darn thing works when written as a simple process, but that isn't Java now is it? Here's the simple:
public class PythagoreanTheorem extends ConsoleProgram { public void run() { println ("Finding C from A and B."); double a1 = readDouble("Input A: "); double b1 = readDouble("Input B: "); double aSq = (a1*a1); double bSq = (b1*b1); double cSq = (aSq + bSq); double c = Math.sqrt(cSq); println ("C = " + c);
I'm having a bit of trouble with using the Scanner and the Printwriter. I start with a file like this (1 = amount of Houses in the file)
1 FOR SALE: Emmalaan 23 3051JC Rotterdam 7 rooms buyprice 300000 energylevel C
The user gets (let's say for simplicity) 3 options:
1. Add a House to the file, 2. Get all Houses which fullfil requirements (price, FOR SALE / SOLD etc.) and 3. Close the application.
This is how I start:
Scanner sc = new Scanner (System.in); while (!endLoop) { System.out.println("Make a choice); System.out.println("1) Add House"); System.out.println("2) Show Houses"); System.out.println("3) Exit"); int choice = sc.nextInt();
Then I have a switch for all of the three cases. I keep the scanner open, so Java can get the user input (house = for sale or sold, price = ... etc). If the user chose option 1, and all information needed is inputted and scanned, the House will be written to the file (which looks like what I typed above).
For this, I use try (PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("Makelaar.txt", false)))). This works perfectly (at least so it seems.)
If the user chose option 1, and all requirements are inputted and scanned, the Houses will be read (scanner) from the file and outputted. For this I use the same Scanner sc. This also works perfectly (so it seems atleast).
My problem is as follows: If a House has been added, I can only read the House(s) which were already in the file. Let's say I have added 2 houses, and there were from the start 3 houses. If option 2 is chosen, the first 3 houses will be scanned perfectly. An exception will be caught for the remaining 2 (just added) Houses. How can I solve this? I tried to close the Scanner, and reopening it, but apparently Java doesn't agree with this
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.
I have an ArrayList of employee and ArrayLsit of bosses, and I want to keep those people in a temporary ArrayList , then ordain alphabetically by name, to sort I use the interface comparator.
The problem comes when I will order 2 ArrayList(workers and bosses), because every time I call I use these functions or not is ordered (sortByNameAlphabetical())
public class Employee { private String name; public String getName() { return name; } @Override public String toString() { return name ;
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)); }
Right now, i'm trying to do is when a user clicks on my GUI button, it would display a text of information on the button they selected. I'm using an arraylist of objects and i'm trying to input the function inside the mouse click function. But I'm not sure how to properly display that information. Here is my GUI code. I'm working on the raven button. I have animal interface, with a parent class of Bird, and child class of Raven. How I could display this correctly...
public class AnimalJF extends JFrame { private JPanel contentPane; private JTextArea textArea = new JTextArea(); /** * Launch the application. */ public static ArrayList<Bird> Birdlist = new ArrayList<Bird>(); public static void main(String[] args) { Birdlist.add(new Eagle());
I am currently working on a program that will read from a .txt file to create an arraylist. I will be working with the objects in the list to perform computations and display the data. The .txt file is in the following format: lastName firstName hoursWorked hourlyRate
With no delimiters. I've messed with this thing way too much in the last 12 hours (only day off for the week ) so variable names etc have changed often. At present the error I am receiving is "error: constructor GrossPayService in class GrossPayService cannot be applied to given types".
import java.util.*; import java.io.*; import java.text.*; class AryListObjects { public static void addEmployee(String firstName, String lastName, double hoursWorked, double hourlyRate) { ArrayList<GrossPayService> employees = new ArrayList<GrossPayService>();
I've this "program" that shall manage to register a dog, show a list of all registerd dogs and delete dogs from the list.. And I'm stuck at the latter one. So I've to classes, one for the dog and one for register/program. This is my main program
package hundRegister; import java.util.Scanner; import java.util.ArrayList; public class HundProgram { private static Scanner tangentbord = new Scanner (System.in); private static ArrayList<Hund> hundlista = new ArrayList<>();
[Code] ......
So, when I enter a name on a dog that exist on my list, it just jumps down to } else { and write that dog can't be found even if I write the exact name on the dog.
I can't see what I'm doing wrong, been trying out different methods now.
I'm making a program for my class's chapter on classes. I need to make a program that makes a grocery list using an array. Here's the assignment from the book.
Write a class named GroceryList that represents a list of items to buy from the market, and another class named GroceryItemOrder that represents a request to purchase a particular item in a given quantity (example: four boxes of cookies). The GroceryList class should use an array field to store the grocery items and to keep track of its size (number of items in the list so far). Assume that a grocery list will have no more than 10 items. A GroceryList object should have the following methods:
public GroceryList() Constructs a new empty grocery list. public void add(GroceryItemOrder item) Adds the given item order to this list if the list has fewer than 10 items. public double getTotalCost() Returns the total sum cost of all grocery item orders in this list.
The GroceryItemOrder class should store an item quantity and a price per unit. A GroceryItemOrder object should have the following methods:
public GroceryItemOrder(String name, int quantity, double pricePerUnit) Constructs an item order to purchase the item with the given name, in the given quantity, which costs the given price per unit. public double getCost() Returns the total cost of this item in its given quantity. For example, four boxes of cookies that cost 2.30 per unit have a total cost of 9.20. public void setQuantity(int quantity) Sets this grocery item’s quantity to be the given value.
I have the assignment mostly done, but the JUnit test case our teacher gave us to test it tests add() an array instead of an array list. For this reason, I need to change my program to use an array. My code is below.
import java.util.*; public class GroceryList { private ArrayList<GroceryItemOrder> list; int num; public GroceryList() { list = new ArrayList<GroceryItemOrder>(10);
How can i sort my ArrayList, which contains cars, with year and used year, i want to sort them first from year, and then from used year . what should i use?
I am trying to add the contents of the iterator to an arraylist so I can do other stuff to it, however I am getting an error when I actually try adding it to the list, stating that
"The method add(Map.Entry<String,myObject>) in the type ArrayList<Map.Entry<String,myObject>> is not applicable for the arguments (myObject)"
Here is what I have tried doing:
Iterator<Map.Entry<String, myObject>> iterator = hash.entrySet().iterator();//hash is my HashMap object ArrayList<Map.Entry<String, myObject>> list = new ArrayList<Map.Entry<String, myObject>>(); while(iterator.hasNext()){ Map.Entry<String, myObject> entry = iterator.next(); list.add(entry.getValue());//error here }
I have a ArrayList of objects of class called HockeyPlayer (ArrayList<HockeyPlayer>). A HockeyPlayer has a String name and int number of goals.
This is my current work for comparing each object in the list to every other and printing them to screen:
Iterator<HockeyPlayer> it = hockeyPlayersList.iterator(); while (it.hasNext()) { HockeyPlayer singleHockeyPlayer = it.next(); //the first one encountered // HockeyPlayer nextHockeyPlayer = it.next(); //the next one encountered
[Code]...
This of course produces some duplication in the print-out: These are the equal hockey players: Who Ever wears jersey. This type of employee is paid: true. This employee has post-secondary education: false. This employee's work is to play. This hockey player has scored 0 goals.
Jason Harrison wears jersey. This type of employee is paid: true. This employee has post-secondary education: false. This employee's work is to play. This hockey player has scored 0 goals.
These are the equal hockey players: Jason Harrison wears jersey. This type of employee is paid: true. This employee has post-secondary education: false. This employee's work is to play. This hockey player has scored 0 goals.
Who Ever wears jersey. This type of employee is paid: true. This employee has post-secondary education: false. This employee's work is to play. This hockey player has scored 0 goals.
The System.out.println("jsp page: .... &> results in the output: "jsp page: movielist - [Title: Die Hard; Budget: 20000000, Title: two days in paris; Budget: 1000000]" so I am confident the objects are being loaded into the ModelAndView correctly. However the output of the block is "${movie.name}" instead of the list of movies. My movie object has a getName() method to return a string (and a setName() method). I am not sure why the System.out.println statement can find the movielist attribute, but ${movie.name} is being treated a plain text. There are no execptions thrown or other indications of errors.
I'm trying to count the number of elements in an ArrayList which also have duplicates. So for example, in an ArrayList of strings which contains cat, cat, dog, horse, zebra, zebra, the answer should be two.
If an element is found to be a duplicate, that element should then be exempt from the search so if that element is found again it should not increase the duplicate count.
Here is my code:
public int countDuplicates() { int duplicates = 0; // TODO: Write the code to get the number of duplicates in the list for (int i = 0; i < list.size()-1;i++) { boolean found = false;
[Code] ....
I know it's wrong because right now it's still increasing the duplicate count for elements that have already been detected as duplicates. How can I make it stop doing this?
What I want to do is this, this is my first class:
public class Footballer { int goals; String surname= ""; String team=""; private static int counter=0; private int dres; }
(this is just the header of the class... And this is my second class, which contains an ArrayList of the first class:
public class FootballTeam{ String teamname=""; String league=""; ArrayList<Footballer> f; }
And this is my third class which contains an ArrayList of the second class:
public class FootballLeague{ String leaguename=""; ArrayList<FootballTeam> ft; }
What I want to do is, know how many of footballers are there in the league? Meaning how many of "f"s are in the "ft"... I remember from C++ it was easy, you just did it something like this: ft.f[i]; (where i is a position), then you'd go through each of them, if you wanted to do something with them, or just ask for it's length, if you needed to know how much footballers are there.
I'm trying this method to get the size of the array in the 2nd class, from the 3rd class (containing an ArrayList of classes of 2nd class, but no luck:
int counter=0; for(int i=0;i<this.ft.size();i++) { counter+=this.ft[i].f.size(); }
I'm getting this: Array required, but ArrayList<FootballTeam> found ---
I made a calculator that does the basic operations but I want to be able to divide more than two numbers by repeatedly entering values using an arraylist and I keep getting the indexoutofboundsexception and I don't know why? I understand the reason behind the outofboundsexception but I can't figure out why in this case. Here is a snippet:
public Double division(ArrayList<Double> list){ Double dnum = 0.0; Double divide = numList.get(0); // Initialize divide to first element in the arraylist for(int i=0; i < numList.size(); i++){
I want to clone some Arraylist, but the compiler apparently are just referencing the values to it's original ArrayList. I don't know what should it be:
package projetoteste; import java.util.ArrayList; import java.util.List; public class TestFood { public static void main(String[] args) { List food=new ArrayList();
[code]....
Notice that ArrayList dailyMeal should be untouchable, but it return the changes that I made in local for-loop iteration although I didn't added nothing to it, just to it's clone.
I'm a total newbie to Java, and until now all I've done was draw some shapes and flags. I'm struggling to understand the code I've been given. I need to access values stored in an ArrayList within another class. Here are the two classes Seat and Mandate:
package wtf2; import java.util.*; public class Seat { public int index; public String place; public int electorate;
[Code] ....
The main class contains code that feeds data from 2 text files into Seat and Mandate. From there I managed to access the date in Seat (at the end):
package wtf2; import java.io.*; import java.util.*; public class CW2 { public static void main(String[] args)throws Exception {
[Code] ....
Now,instead of getting just the mp for Edinburgh South I need to get the vote values, compare them to each other, take the second biggest and display the associate party value. How to access data from that Array to get started at least.
