Remove Multiple Elements From ArrayList?
Dec 27, 2014
I have an ArrayList of tens of thousands of elements, and want to remove the items at a given set of sorted indices like {1,5,29,318,499,583}. It seems like this operation could be performed in linear time and space by first finding a cumulative sum of the shifts needed to move everything to their right positions and then shifting every item. On the other hand, removing and shifting one by one would seem to require many more shifts. Is there a way to do this in Java's ArrayList?
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Apr 30, 2014
remove duplicate elements in array using with java
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Mar 13, 2014
Right now i am working on some java using BlueJ and trying to insert and remove data from an arraylist through a public class or from a new class.
I want it to have it as like a database were you can add and remove data but have a limit of storing.
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Aug 24, 2014
Referring Code 1, the book says line 16 of the code removes the element "Three" but line 17 does not remove the element "Four" because of Statement 1. The question is does remove(Object o) method invoke the == or the equals method because statement 1 and 2 seem to be in conflict
Statement 1:
Two objects are equal if their object references point to the same object. (which is nothing but definition of ==)
Statement 2:
The author refers to Statement 1 and says "As mentioned earlier, the method remove compares the objects for equality before removing it from ArrayList by calling method equals."
Java Code:
import java.util.ArrayList;
public class DeleteElementsFromArrayList {
public static void main(String args[]) {
ArrayList<StringBuilder> myArrList = new ArrayList<>();
StringBuilder sb1 = new StringBuilder("One");
[Code] ....
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May 11, 2015
I have a 2D arraylist, named as adjLists, which contains arraylists, containing values like these. Each two values are a "pair" and each third is a "flag" for the pair.
[278, 106, 0, 397, 36, 0, 59, 208, 0, 366, 221, 0]
[366, 221, 0, 397, 36, 0, 132, 390, 0, 278, 106, 0, 295, 0, 0]
I use code above to search for specified value pairs in these lists. vertexnum is the number of "sub arraylists" in adjLists.
for (int l = 0; l < vertexnum; l++) {
if (adjLists.get(l).get(0) == p.x && adjLists.get(l).get(1) == p.y) {
for (int h = 0; h < adjLists.get(l).size(); h += 3) {
for (int g = 0; g < vertexnum; g++) {
if ((vertexSprite[g].getX() + vertexSprite[g].getWidth() / 2) == adjLists.get(l).get(h)
[Code] ....
This code is to search exact values and replace their flag in every occurences. It can not find all the occurences of the values/pair in the lists, it replaces flag value only a few time. Value of score should be incremented with plus 1 after each found occurence, but this code increments it more than the number of matches.
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Dec 2, 2014
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?
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Oct 5, 2014
When this program runs it gives me
workbook.Contact@46e5590e
Number of contact: 1
The number of Contact that I input is just one when I run the program so the Number of contacts: 1 is correct, but it gives me workbook.Contact@46e5590e instead of printing out all the contacts stored inside the Contact class. Yes I do loop through the ArrayList and I also have a method inside the Contact class, the printNameAndPhone(), which prints out the name as well as the phone number but how do I incorporate the printNameAndPhone() method (located in the Contact class) inside the print() method (located inside the AddressBook class)???
Basically I'm asking how to access all the elements in the ArrayList<Contact> addressBook = new ArrayList<>();??My main class AddressBook
package addressbook;
import java.util.Scanner;
import java.util.ArrayList;
public class AddressBook {
[code]....
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Feb 24, 2015
how to read and understand the API's. I've got an array list and I was wondering if there was a method that can randomly re arrange the elements in terms of their index positions.
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Feb 18, 2014
I'm new to object oriented programming, my previous experiences have been in C. I was given an assignment to implement an operation to transform a list of data by creating a partitioning algoritm.
import java.util.*;
public class Partition {
public static void partitionWithSetGet ( List<String> theCollectionOfData ) {
int i, j;
while(i <= j){
int Result = theCollectionOfData.get(i).compareTo(pivot);
int Result = theCollectionOfData.get(j).compareTo(pivot);
[code]....
I want to grasp the this concept in greater detail, then I can use the Java API to figure out the syntax!
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Mar 4, 2014
I have a data structure such as: ArrayList<ArrayList<Integer,String>
The data looks as [[1,2,3] [3,4] [99,98,40,32,45,65,1]]
I am trying to access each element and put them into a hashtable such as:
Hashtable<Integer,String>
With what I am doing below I am getting an out of bound error but can't see any other way of accessing the element
public static void hash(ArrayList<ArrayList<String>> list)
{
for(int i = 0; i < list.size(); i++)
{
int cnt = 0;
for(int y = 0; y < list.size(); y++)
{
if (! hashMap.containsValue(list.get(i).get(y)))
{
hashMap.put(cnt, list.get(i).get(y));
cnt++;
}
...
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Feb 10, 2014
For example, if I have a class called Teacher with the constructor:
public Teacher(double yearsTeaching, boolean isMale, double age)
{
this.yearsTeaching = yearsTeaching;
this.isMale = isMale;
this.age = age;
}
How would I add it to these parameters to my ArrayList in my Tester class?
List<Teacher> teachers = new ArrayList<Teacher>();
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Oct 25, 2014
I have to make a retail item class that has description, price and quantity. I then have to make a CashRegister class that calculates subtotal, tax, total and displays it (toString). I also have to make a driver class to call the methods from main. I have no clue what I am doing and what I have done does not work. I am trying to make it sort of like a cart, in the CashRegister it should ask the user to enter the description, quantity purchased and the price. Then it would send that to the arraylist of retailitem. I am having trouble using those items in my other methods and then do not know how to call those in the driver class.. So here are my classes:
public class RetailItem {
private String description;
private int quantity;
private double price;
public RetailItem(){
description = "";
quantity = 0;
[Code] ....
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Oct 25, 2014
Alright.. So I have to make a retail item class that has description, price and quantity. I then have to make a CashRegister class that calculates subtotal, tax, total and displays it (toString). I also have to make a driver class to call the methods from main. I have no clue what I am doing and what I have done does not work. I am trying to make it sort of like a cart, in the CashRegister it should ask the user to enter the description, quantity purchased and the price. Then it would send that to the arraylist of retailitem. I am having trouble using those items in my other methods and then do not know how to call those in the driver class...
So here are my classes: [URL] ....
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Nov 16, 2014
I have declared an array list that will store data type of 1 Character and 2 integer. The data that will be store in this list is
1. A = {0 3}
2. B = {0 5}
3. C = {0 3}
4. D = {0 3}
5. E = {0 5}
6. F = {0 6}
Now here the alphabets are routers and integers are there con1 and con2 respectively. I have a set of router={ A,B,C,D,E,F}.
Step 1:I have to subtract con1 from con2 i.e. (3-0) of all the routers and
Step 2: then put the router having largest value in new set 1 and
Step 3: then this router will be subtract from the router set.
Step 4:then again I have to repeat the step 1 until the value of routers become <= 1.
Now what I did is I defined 3 arrays first is String array that stores names of routers, 2nd array that stores the first value and 3rd array that stores the second value. I can find the largest value but how to store the name of router against the largest value in the set.
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Jan 24, 2014
I just started playing around with Java for awhile, but got caught up in a problem when using ArrayList.
CinemaAppMain
public class CinemaAppMain {
public static void main(String[] args) {
new CinemaApp().start();
[Code]....
I am trying to get the movie name and theatre title from their ArrayList, and I know I need to go through the movie list & theatre list to find their name & title, and compare it with the user input and print out the result.
I use for(int i=0;i<movies.size();i++) to go through the the movie list, and I tried using for(int i=0;i<theatres.size();i++) to go through the theatre list. But when I printing multiple time with different user input value, it will show me strange result (screening have same movie name & theatre name, the else if statement is printed below the user input, user input is printed more than once after the first time).
Edit: I know its wrong for me to use nested for loop,if not, another solution is needed to get the item inside both of the list. (getting the "title" from movie list & "name" from theatre list)
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Oct 25, 2014
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] ....
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Jan 13, 2014
I have a code to resize a single rectangle. I would like to display and resize multiple rectangles independently and according to my research on the net, the best way is to use an arraylist. So I modified the code in this sense, except ...when I run the code, the rectangles appear good but impossible to resize. I think the problem comes from mousePressed, Released, Dragged and Moved methods. When I use the mouse to resize the rectangle, nothing happens. The code does not interact with the arraylist, and therefore with rectangles it "contains". Resizing is my main class, the MouseAdapter is in the Resizer class (below).
Resizing component; boolean dragging = false; // Give user some leeway for selections.
final int PROX_DIST = 3; Path2D.Double selectedPath; public Resizer(Resizing rz) {
component = rz; component.addMouseListener(this);
component.addMouseMotionListener(this);
[Code] .....
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Oct 25, 2014
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]....
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Feb 5, 2015
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class array
{
public static void main(String[] args)
[Code] ...
Is there a way to write this, where, alpha is one array.
Write a program that declares an array "alpha" of 50 elements of type "double". Initialize the array so that the first 25 elements are equal to the square of the index variable and the last 25 elements are equal to three times the index variable. Output the array so that 10 elements per line are printed.
If I have an array of 50 integers, can I break that to read in lines of 10?
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Jan 12, 2015
I am trying to make a 2d array that keeps track of comparison counts. what I have so far works ok but writes over the previous elements with 0. can't seem to find where I am re-initializing the previous elements.
//this is one of my fill sort arrays
public void fillSelectionArray(int index, long countSum) {
//rand = new Random( );
//for ( int i = 0; i < listsize; i++) {
selectionList[ index -1] = countSum;
// }
[Code] ....
I know I am missing something just not sure what.
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Dec 8, 2014
I have i am trying to implement tooltip through javascript, like when we click on an image link tooltip should be displayed and it should have close button/ close image to close that tooltip.like the same way i will have multiple images on page, when ever i click on the images all tooltips should be displayed on the page when ever i want to close that then only it should close through close button on tooltip.can we do it through java script or will go for jquery.
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May 5, 2015
I'm very new to Java, and I am creating a program that takes multiple user input to create one face. I have a class for the eyes, nose, lips, and headshape. For some reason, my program is not drawing the graphics. ***for question purposes, I have only included my head shape class and my test class****
my "test" class:
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class FaceTest
{
public static void main(String[] args)
{
String head = JOptionPane.showInputDialog("Would you like a circle, square, rectangle shaped head?: ");
[Code] ....
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Feb 28, 2014
I'm trying to create my own arraylist using Collection. My program doesn't do anything. Obviously, I haven't a clue.
import java.util.Collection;
import java.util.Iterator;
public class MyArrayList<T> implements java.util.Collection<T> {
private int size = 4;
private T[] mArray;
public MyArrayList(String[] args) {
[Code] ....
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Jul 11, 2014
I'm trying to make a calendar that, when you click on the date, the result are stored in a map and visualized in a table that refers to a container.
I successfully created the map mechanism, but I have a problem on the list....
I add the rows in this way:
Object newItemId = container.addItem();
Item riga = container.getItem(newItemId);
riga.getItemProperty("Timestamp").setValue(fara);
riga.getItemProperty("Date").setValue(asa);
.
How can I delete a row in the list, when all I have in input is the "Timestamp" information, in a Long value?
BTY, I'm using NetBeans with Vaadin extension
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Apr 12, 2014
My remove(item E) method is working fine if I remove an item that is in the list. However, it has an error when I try to remove an item which is not on the list!
Linked List Class
import java.util.NoSuchElementException;
public class LinkedList<E>
{
private Node<E> head; // head node of the list
private int size = 0; // number of elements that have been added to the list
// Returns the element at a specific list index.
// Big-O: O(n) (due to the nodeAt call, which must traverse the list)
public E get(int index)
[code]...
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Jan 16, 2015
I want my jSpinner value "0" to be removed on button click. and I want my jSpinner and jFormattedTextfield and jTextfield value "0" to be Highlighted(e.g: like highlighted by mouse double click) on button click.By removed I mean: nothing to be in the jSpinner. empty as any textfield. the jSpinner default value is 0 and on Click I want the value of the jSpinner to be removed and Highlighted, I need both examples code.
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