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....
I managed to retrieve data, and set data in my own ways in which I like. But my problem is, if the file does not contain anything (fully empty), when I try to use my
set("", "");
method, it only sets the last one that is called.
Example:
set("section1", "section1Item");
set("section2", "section2Item");
set("section3", "section3Item");
Only section3 would get set, and not the others.
Otherwise, if the file contained a section already, then each section (section1, section2, section3) would get set.
Here's how I set the data to the file:
public static void set(String section, String data) {
files.openFileWriter();
files.file.delete();
reCreateFile();
String beforeItem = section + ":" + files.dataList.get(section);
if(files.hasReadData) {
[Code] ....
And here is how a retrieve the data and set them to my arraylist/hashmap:
public void getData() {
String line = null;
openFileReader();
StringBuffer sb = new StringBuffer();
[Code] ....
I managed to retrieve data, and set data in my own ways in which I like. But my problem is, if the file does not contain anything (fully empty), when I try to use my
set("", "");
method, it only sets the last one that is called.
Example:
set("section1", "section1Item");
set("section2", "section2Item");
set("section3", "section3Item");
Only section3 would get set, and not the others.
Otherwise, if the file contained a section already, then each section (section1, section2, section3) would get set.
Here's how I set the data to the file:
public static void set(String section, String data) {
files.openFileWriter();
files.file.delete();
reCreateFile();
String beforeItem = section + ":" + files.dataList.get(section);
[code]....
And here is how a retrieve the data and set them to my arraylist/hashmap:
public void getData() {
String line = null;
openFileReader();
StringBuffer sb = new StringBuffer();
[code]....
Working on my final which is due today, its' and Inventory Program which I have been working on for the last 5 weeks. My Buttons on my GUI Add/Delete doesn't add items to my inventory. I'm not sure exactly what wrong with my code, I'm not getting any error and the Program compiles just fine, I just can get the Items to add of delete.
my Delete button starts on line 281
my Add Button begins on line 319
//
/** Purpose:the purpose of this software is to display inputs as wells as the stocks and price of inputs,
*as well as display a 5 % restocking fee per dvd and for the entire Invenotry of each object.
*adding a GUI to the code. Adding a Previous button to the existing code allowing the user to cycle through
*the Inventory list freely. Also adding a graphics logo to page. adding more buttons and allowing program to
*save new items added to the inventory.
**/
//Needed Imports for GUI
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import javax.swing.border.EmptyBorder;
import java.io.File;
import java.io.IOException;
[Code] .....
So I'm trying to write a method which returns the number of vowel characters in arraylist. My idea is to convert the arraylist element by element to array each time iterating through the array counting the vowels of that element. When I started I immediately got an error(surprise, surprise). Excuse me if the problem is too simple, but I am very new to programming.
At line 9 I get the following error "Type mismatch: cannot convert from String to int". I want to get the element at this position, not to convert to int..
ublic class One {
public static void main(String[] args) {
ArrayList<String> bla = new ArrayList<String>();
bla.add("aaa");
bla.add("brr");
bla.add("unn");
}
public static ArrayList<String> averageVowels (ArrayList<String> list){
String[] arrListWord = list.toArray(new String[list.get(0)]);
return list;
}
}
I have an array list in my GUI class of an aplication , the app reads in 3 fields from the user and saves these to an array list allowing the user to enter more fields to be added to the arraylist, when displaying back out to the user the same entry displays multiple times, for example if i entered , a,b,1 then c,d,2 and then e,f,3 into the app when i press my display button it would just throw back e,f,3 three times rater than the three different entries...
Constructor and instance variables
private String name;
private String number;
private int year;
private int count;
private ArrayList<StudentData> myList;
private StudentData myData;
[Code] .....
This is supposed to be a method that adds stars after each item in the list.
Java Code:
import java.util.ArrayList;
public class ClientProgram {
public static void main(String[] args) {
ArrayList<String> list = new ArrayList<String>();
list.add("the");
[Code] ...
I'm guessing it's because list.size() changes, though but it should only find that value in the beginning, so it shouldn't be a problem?
How do you remove from an ArrayList at a particular index then add back to that same index without the removal causing the ArrayList to compensate for the loss of them item and moving the empty space to the end of the array list?I've tried:
public void dischargePatient(int bedNumber) {
if (bedNumber < beds.size()) {
beds.remove(bedNumber);
}
}
But this moves the bed at bedNumber to the end of the ArrayList after removing the patient from the bed. How do I keep it at bedNumber?
I have a JSF application with this code in the xhtml page:
<h:selectOneListbox id="selectProduct" size="10" style="width:10em; font-family:monospace" value="#{mybean.product}">
<f:selectItems value="#{mybean.products}" />
</h:selectOneListbox>
and the corresponding snippets of the Java code are:
// Class member variables
// ...
private String product;
private ArrayList<String> productValues;
private ArrayList<String> productLabels;
private SelectItem[] products;
// ... Various properties etc.
public String getLocation() { // Displayed on a page
[code]....
Most of this works correctly using only ArrayList SelectItem products without the two ArrayList and the separate SelectItem[], and the values and labels are put directly into products here. The menu works and I can select an item. However, I am unable to find the correct method for finding the index in the submit method,namely:
public void submit(ActionEvent e) {
showProduct = true;
prodNum = products.indexOf(product); // --- Here is the problem!
updateProduct();
}
which has not been changed here. In spite of trying out various ideas, prodNum always returns with -1, which means it cannot find the index of the selected product, where product is a String. Everything else seems to work correctly, and products.get(prodNum).getLabel() works if I manually give prodNum a valid index, but because it's -1 it fails.
I am not sure how to go about doing this, An ItemEvent.Selected constant is the hint given to me but i dont know how to start it.
My Array is : private ArrayList billItems = new ArrayList();
My method is : private void beverageJComboBoxItemStateChanged( ItemEvent event )
I've two classes: Student and ArrayListExamples (which has my main method in it).
The student class acts pretty simply at the moment with a constructor that takes a name, surname and ID number. I've tested it and it seems to be working. My issue is with adding an object to an array list, here is my effort:
public class ArrayListExamples {
private static int MAX_SIZE = 50;
static Scanner sc = new Scanner(System.in);
public static void main(String[] args) {
ArrayList<Student> students = new ArrayList();
[code]....
I know the last loop to add the student objects is wrong.I'm calling the student ArrayList add method with a student object whose constructor requires two strings and an integer. Why isn't this allowed?
package eg.edu.guc.iphone.tiles;
import java.util.ArrayList;
import eg.edu.guc.iphone.Location;
public class Square extends Piece {
private ArrayList<Location>possibleMoves;
[Code] ......
Ive set up a list to when a user creates an element it will be added to the entire list, but when i return to the main menu the Element isnt added.
Here is the code
public void setElement(int atomicNum, Element e){
if (ElementHasData(atomicNum) == false) {
if(atomicNum < MAX){
list[atomicNum] = e;
atomicNum++;
[Code] ...
Here is what the code intiates
~MAIN MENU~
Please select an option you wish to activate
1) Print All Elements
2) Print One Specific Element
3) Add an Element
4) Edit an Element
3
What is the atomic number of the Element you would like to add
Numbers only valid 1-113
1
Enter element name
Hydrogen
Enter element Symbol
H
What is the Elements weight
1.01
NEW ELEMENT ADDED!
[Code] ....
~MAIN MENU~
Please select an option you wish to activate
1) Print All Elements
2) Print One Specific Element
3) Add an Element
4) Edit an Element
But then after i try to print the specific element
~MAIN MENU~
Please select an option you wish to activate
1) Print All Elements
2) Print One Specific Element
3) Add an Element
4) Edit an Element
2
What is the atomic number of the Element
1
that element does not exist would u like to create this element Enter yes or no
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()
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.
I'm having an issues with adding integer values to a string list. The question is asking me "the method should iterate over runners, and for each runner generate a random number between 90 and 180 (inclusive) which should be used to set the time (in minutes) for that runner."
I have been able to get the random number and iterating over the runner arraylist but I haven't been able to figure out how to add the values generated into the runners list. I am also using BlueJ.
Here's the whole code I have at the moment:
import java.util.*;
import java.io.*;
import ou.*;
import java.util.Random;
/**
* Write a description of class MarathonAdmin here.
*/
public class MarathonAdmin {
// instance variables - replace the example below with your own
[Code] .....
I'm trying to fill my jtable with an arraylist. The problem is the jtable is in an extended class and the arraylist in the mainGUI. Now how can I fill the jtable with the arraylist?
That's the arraylist in my MainGUI
BufferedReader in = null;
ArrayList<String> data = new ArrayList<String>();
try {
in = new BufferedReader(new FileReader("1.dat.txt"));
String str;
while ((str = in.readLine()) != null) {
data.add(str);
[Code] ....
I don't really get the concept of how I "insert" an item into an array. I get a cannot find symbol error when I try to. I think its because I'm losing focus. What sort of code would "insert" an item into an array? I just want a goal of conceptually how I would do it.
Anyways, here are the instructions for the exercise:
Write a new class method, insert, for the Item class that takes three arguments - an Item[] array, an Item newItem, and an int k - and inserts newItem into array at index k, discarding the last item of the array (that is, the item originally at index array.length - 1).
Here is the uneditable code:
public class Item {
private int myN;
public Item( int n ) {
myN = n;
}
public String toString()
[Code] ....
I get a cannot find symbol error, but I thought I was doing as I was supposed to. I thought you had to have an ArrayList to be able to insert or delete an item from an array. How can you take a primitive object, like an array, and insert something into it. My idea of it was a[i] would be replaced with a[i + 1]. I know I'm getting this concept wrong because that's what I tried to do.
I am trying to have a user select from a printed out array list, instead of having the user type in the "bill type" each time there is a bill to avoid user error as much as possible. For example I would like to have it print out like this:
"Select bill type from list:
1. Rent
2. Car
3. etc..."
and I would like the user to choose a number and not type in the "bill type". I don't want to use "Switch case" because it would need to be an expanding and I don't think "switch case" can do that.
Here is the code:
package homebudget;
class Spending
{
//Do i need a totalAmount variable?
String type;
double amount;
int year, month, day;
public Spending()
[Code] ....
case 2:
//Give option to enter a new expense or pick from list.
//How to do this? If Statement that doesn't list duplicates, or a while search?
resp = JOptionPane.showInputDialog("Enter the type of expense:");
type = resp;
resp = JOptionPane.showInputDialog("Enter the amount of the expense:");
amount = Double.parseDouble(resp);
[Code] .....
Question 1: I am working on an assignment where I have to remove an item from a String array (see code below). When I try to remove an item after entering it I get the following error "java.lang.NullPointerException." I am not sure how to correct this error.
Question 2: In addition, I am having trouble figuring out how to count the number of occurrences of each string in the array and print the counts. I've been looking at other posts but they are more advanced and I have not yet learned how to use some of the tools they are referring to.
private void removeFlower(String flowerPack[]) {
// TODO: Remove a flower that is specified by the user
Scanner input=new Scanner(System.in);
System.out.println();
System.out.println("Please enter the name of the flower you would like to remove:
[Code] ....
I am working on a problem where i have to create a 2d array with given input of the dimensions (odd number) of array, along with a number within the array and to then print out all of the numbers surrounding that number.
Anyway, i am working on simply making the spiral, which should look like the one below.
n = 3
7 8 9
6 1 2
5 4 3
where the 1 always starts in the center with the 2 going to the right, 3 down, then left etc. etc. I was able to create the code by starting on the outer edges rather than the center and working my way to the middle, however my code always starts from the top left and goes around to the center where it needs to start from the top right. I am having trouble altering my code to meet this criteria. This is what i have thus far.
import java.io.*;
public class Spiral
{
public static void main(String args[])throws IOException
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter the number of elements : ");
int n=Integer.parseInt(br.readLine());
[Code] .....
I am working on a text based adventure game. (This is NOT OOP at all) The problem comes in at my second if statement inside my loop, it is not adding 1 to my array locations[] it keep printing location[0] then a 1 at the end. Not really sure what is going on here. I would like it to when I type "Go north" it adds 1 to locations[]
E.G
locations[0]
Go north
locations[1]
go north
locations[2]
package com.PenguinGaming;
import java.util.Scanner;
public class Game{
[code]....
I have a main class:
Java Code:
public class Main {
public static void main(String[] args) {
Player[] playerList = new Player[] {new Player("Daniel", 3, 3, 2, 1, 1, 3),new Player ("Player2", 2, 4, 1, 6, 3, 2)};
System.out.println(Player.getPlayer());
}
} mh_sh_highlight_all('java');
[code]....
and whenever I run it, it prints out the last player, so I was wondering how to identify them separately, but still use the array, as (I believe) it is the most efficient way.
Something like ArrayList<Object>[] = new ArrayList<Object>[]();
View Replies View RelatedI'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);
[Code] .....
I am working on a assignment that has to do with array lists, it mainly has to do with adding new elements, telling then where it is it located, if the memory block is empty , ect. so far i have been having problems with my indexOf method which should display the array cell number that a input element E is in, and if it is not in there it should display a -1.
public class MyArrayList<E>
{
private E[] data_store = (E[])new Object[2];
private int sizeofa = 0;
private void resize()// makes the array list bigger if need {
E[] bigspacemaker = (E[])new Object[data_store.length * 2];
for(int x = 0 ; x< sizeofa ; x++)
[Code] ....
Error message:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 512
at MyArrayList.indexOf(MyArrayList.java:28)
at MyArrayListDemo1.main(MyArrayListDemo1.java:26)