HashSet And Iterator - Accessing Element Contained In The Object?
Sep 23, 2014
I'm not new to java but i'm not able to solve the following issue: I have a class
public class Localizzazioni implements java.io.Serializable {
private <complexType> id;
public getId().......
public setId().....
The complexType is a class defined in the code somewhere. Now I want to access it in another class I have
Set localizzazioni = new HashSet(0);
localizzazioni=opere.getOiLocalizzazioneOperas(); -- this object give an object of tyoe HashSet
for(Object object : localizzazioni) {
object.get......... // i cannot use any method defined in the class Localizzazioni
}
Why I cannot write inside the for object.getId() and using it?? In other word how i can access the element contained in the object?? the object is an iterator of type Localizzazioni . The class Localizzazioni has some method but i cannot use them? why ....
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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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Oct 14, 2014
Scanner in = new Scanner(System.in);
ArrayList<rand> selectedRand = new ArrayList<Rand>();
selectedRand.add(new Rand(in.nextLine()));
I have created the most minimal code for creating an array list. I was wondering what the basic syntax of accessing objects methods that are within an Array List. So if I was to trying and get a method such as [.returnValue,] how would this look within a Rand object that is declared in a Array List Since you cannot simply declare a new Rand object and say:
newRandObject.returnValue();
And you must go through the actual slotted portion of the array list. I have searched the web and my text book for an example however none are provided.
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Mar 10, 2014
I have a situation where I have 2 classes and an array of objects which are causing me trouble.
The object type is one I have created - it is made from a class which is neither of the 2 classes I previously mentioned.
The array is created and occupied in Class1 and the problem arises when I try to reference one of the element from Class2.
At first I forgot the the array would be local to Class1.main so I made the array a global variable using:
Java Code: public MyObjectType[] myArray; mh_sh_highlight_all('java');
Then I tried accessing an element (2) from Class2 using:
Java Code: Class1.myArray[2] mh_sh_highlight_all('java');
However I get errors saying that I can't access the static variable from a non-static context.
I understand a little bit about static and non-static objects/methods but don't know how to fix this. Do I need to include "static" in the array declaration?
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Dec 29, 2014
public class BookExamples {
String title;
String genre;
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println("Hey");
[code]...
Eclipse gives me an error for b1.genre = "hey"; saying "Syntax error on token "genre", VariableDeclaratorId expected after this token". I am learning from a HeadFirst Java book that is all in Java 5.0 version which may be part of the problem.
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Jun 30, 2014
I got a strange (!?) behavior using an FXML annotated object ...
Consider the following:
You got an app with FXML build UI.
There is a button called connectB which is @FXML annotated...
In the initialize method of my app I disable this button.
After the startup of my app I want to connect to a DB ...
Therefore I use an Task<Void>
I put everything together in one class ( the main application class )
Here is the code...
public class MainApp extends Application implements Initializable{
// ... several other objects
@FXML
private Button connectB;
@Override
public void initialize( URL location, ResourceBundle resources ) {
connectB.setDisable( true );
[Code] .....
The connectB is not null in the initialize method but later in the task class ....
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Feb 24, 2014
I've tried a couple ways to do it, and they don't work. I'm aiming for functionality like I got with the regular for loop, but from an enhanced for loop. Is this simply beyond the scope of an enhanced for loop, or am I just not getting the right syntax?
TestObject to1 = new TestObject("first", 11);
TestObject to2 = new TestObject("second", 12);
TestObject to3 = new TestObject("third", 13);
TestObject to4 = new TestObject("fourth", 14);
TestObject to5 = new TestObject();
List<TestObject> testList;
testList = new ArrayList<TestObject>();
[code]....
The TestObject class is simply an int and a String, with getters getInt and getString. It all works fine with the regular for loop.
edit: I should probably mention that I know what I have in the enhanced for loop now will only display the class name and the hash. I've tried adding the .getString and .getInt, and tried a few other ways to make it work. I just reverted to this because it compiles and runs
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Apr 1, 2013
I have this piece of code I wrote a while ago to test something. The issue is accessing a private field of Base class in Base but of a Derived object.
Here is the code:
class Base
{
private int x;
public int getX()
[Code]....
The commented code does not work but casting d to Base does.
Forgot to mention that the compilation error is that x has private access in Base.
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Jun 1, 2014
I want to run a program to add an element as the third element of stack without changing rankings, I am trying to use two stack and I don't know how to push the top of first stack in the second: push(top(); this line
public void ADD(int element,int i ){
if(isEmpty(true)){
push(element);}
else{ makeNull();
while((i<=3) && (isEmpty(false))){
push(top();
}
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Feb 4, 2015
I want to know is there any way we can call parent class method using child class object without using super keyword in class B in the following program like we can do in c++ by using scoop resolution operator
class A{
public void hello(){
System.out.println("hello");
}
}
class B extends A{
public void hello(){
//super.hello();
System.out.println("hello1");
[code]....
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Apr 17, 2014
I need the user to enter the name of a file and check if the word is contained in the dictionary file.
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Scanner;
public class SpellChecker{
public static void main(String[] args){
[code]....
I need to read the file and separate the words and save them in a collection after read another file and search each line for one of the words in the collection.
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Sep 19, 2014
I need to make this program work. It is supposed to count the words contained in the Gettysburg address. I went wrong somewhere but don't know where.
import java.util.Scanner;
public class gettysburgAddress {
public Static void main(String[] args) {
String URLString = "http://cs.armstrong.edu/liang/Lincoln.txt";
[Code] .....
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Feb 21, 2015
Returning true from getScrollableTracksViewportWidth() makes the table (or other Scrollable) size its width to match the viewport. I need the opposite: for the viewport to expand its width to accommodate the table (of course, limited by the constraints imposed by the scroll pane's container's layout manager) without reducing column widths i.e. setAutoResizeMode(AUTO_RESIZE_OFF).
I have achieved this by overriding
getPreferredScrollableViewportSize(): JTable table = new JTable() {
@Override
public Dimension getPreferredScrollableViewportSize() {
return new Dimension(super.getPreferredSize().width,
super.getPreferredScrollableViewportSize().height);
}
};
Now when the scroll pane is added at BorderLayout.CENTER and the frame is pack()ed, all columns of the table are displayed, without need for a horizontal scrollbar.
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May 2, 2014
I have been working on this for hours and cannot get it to work properly. The program is to count the number of characters contained in both strings and display the results. It is also to display the final statement, but only once. This version has a complete statement for each matching character.
import java.util.Scanner;
public class CountMatches {
public static void main(String[] args) {
String firstStr = ("");
String s1 = firstStr;
[Code] ....
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Dec 10, 2014
A file has the data of the subjects and name of professors. The file contains line for each subject. The line starts with professor Name followed by the Subject name.
Harry Williams Advanced DBMS
James H Computer Networks
Sasha Ben Artificial Intelligence
Harry Williams Software Engineering
Palbo Kastro Formal Languages
Alex W Advanced SE
James H Operating System
Harry Williams Theoretical Foundation
Write a program with setter getter method to read the file, and then write a class to store several professors in a hashset (Single Key and Multiple Values).The program should be able to display all the professors in the set and allow the user to search for a professor.
Input:
Professor Name: James H.
Then the Output will be:
Subjects Taken by the professor: Computer Networks, Operating System.Display No Classes available if the professor name does not exists .
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Mar 23, 2015
I am trying to write a hashset to a text file. Normally, I have no issues with writing to txt as it is simple for me. However, in this case I am absolutely clueless.
A bit of background about the class: it is a hashset of ComputerScientist objects with 2 fields; name, and field of research (and yes, I know what I put to fill up the HashSet does not count, I was only trying to test to see if I could get this to work).
I know the basic setup to use filewriter to save strings to a txt, but I am getting confused with the HashSet element of it.
import java.util.HashSet;
import java.io.FileWriter;
import java.io.IOException;
/**
* Write a description of class ComputerScientistSet here.
*/
public class ComputerScientistSet {
private HashSet<ComputerScientist> computerScientistSet;
[Code] .....
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Nov 18, 2014
Having trouble adding Class (Dollar) objects to a HashSet (money), i have done this before with arraylists and i understand that HashSets are different in that they cannot contain duplicates. Currently when this code is compiled i am getting "null" printed when I run the "howFullDatWallet" method.
import java.util.*;
public class Wallet {
private HashSet<Dollar> money;
private int walletSize = 0;
private int walletFiller = 0;
/**
* Constructor for objects of class Pocket
*/
public Pocket(int walletCap)
[code]....
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Apr 20, 2014
I have a HashSet, which I created to prevent duplicates upon output, but of course it's printing duplicates(or else I wouldn't be posting this). The order of my output does not matter, nor the input. The data type is String in the format (x + "," + z), where x and z are integers, creating a collection of coordinate sets. So to prevent the output of duplicates, I'm trying to get rid of the duplicates before they are added to the collection.
I've tried doing a '.equals()' string comparison but what happens is, since my string is added via one variable, it compares itself to itself and if itself equals itself it won't be added to the collection. I really need to keep this as a comparison of a single variable, because creating a key for each value would be sooo ridiculous for this volume of inputs.
So, with that being said, I would like to add one copy of the string, discard the duplicates, and do this thousands of times..
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Mar 12, 2014
What is the difference between HashSet, TreeSet and LinkedHashSet?.One difference between HashSet and TreeSet is that TreeSet is sorted, whereas HashSet is not sorted. I dont know the other differences
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Apr 3, 2015
I'm fairly new to java, and is just building small programs to get the feel for the language. How I can improve this code.
import java.util.Set;
import java.util.HashSet;
import java.util.Arrays;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
enum DateValidator {
DDMMYYYY(0, 2, 4),
MMDDYYYY(2, 0, 4),
YYYYMMDD(6, 4, 0);
[Code] ....
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Jan 12, 2015
Is there any way to find how many number of elements are landing in same bucket in HashSet. I know Reflection could be one way but i am not able to design a program for that.
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Apr 4, 2014
I need to find out if one array list is a sub-sequence of another. The elements in the first list all need to be in the second list and must be in the same order. So s1<n, t, a> is a sub-sequence of s2<q, n, f, r, t, d, a>, but s1<a, a, t> is not a sub-sequence of s2<a, t, a>. I need to use iterators to go through each list, and I should only go through each list once (since it has to be in the same order) so nested loops don't seem like they would work because it would start at the beginning of one list every time it moved to another element in the outer loop's list.I seem to have an issue where the itr1. next()
is ignored when in an if statement.
My current code just stalls and will never stop running. I've also switched things around and put the not equal check after the if it is equal and it throws a NoSuchElementException.
import dataStructures.*;
public class Subsequence3
{
public static void main(String[] args)
{
ArrayList<Character> s1 = new ArrayList<Character>();
s1.add('n');
s1.add('p');
s1.add('a');
[code]....
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Nov 12, 2014
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
}
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Mar 25, 2015
I am trying to use an iterator instead of a foreach loop to go through a list of inventories to see if a car is rearDrive and count how many are rearDrive but somehow I seem to be missing something that the counter isn't working as expected.
public int howManyAreRearWheelDrive(){
int i = 0;
int counter = 0;
int inventSize = inventory.size()-1;
while(i < inventSize){
boolean wheelDrive = inventory.get(i).getIsRearWheelDrive();
if( wheelDrive == true){
counter++;
}
}
return counter; // returning here doesn't give me anything
}
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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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Feb 8, 2015
As part of a homework assignment in my 1st Java Class, I am creating my own Circular Generic LinkedList and Array class. My class uses the Queue Interface Extends Iterable but I am creating my own methods to work with. For the most part, I believe I have been successful in creating the class aside from one method. That method is the Iterator<E> iterator().
/**
* Return a fail-fast iterator, which throw a java.util.ConcurrentModificationException
* if the client modifies the collection (via enqueue(...) or dequeue()) during iteration.
*/
@Override
public Iterator<E> iterator() {
I don't understand how an iterator, let alone a "fail-fast" iterator ties into my project. I've spent hours reading up on a way to imploy my own generic fail-fast iterator but to no avail.
I feel like I could come up with some workable code if I knew what the point is to useing a user-defined, non Java Library iterator is to do.
As well, does throwing a ConcurrentModificationException require a try and catch block?
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