Okay, I'm having a problem with my LinkedList. When I run the driver program it's telling me that I have no "add" method and I don't know what's going on.
Driver Program:
public class TestLinkedList {
public static void main(String[] args)
{
MyLinkedList<String> L = new MyLinkedList<String>();
L.add("Browns");
L.add("Ravens");
L.add("Steelers");
[code]....
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]...
I have a LinkedList class that implements a game.
I want to create a list and populate it when a LinkedList object is created .
.
The game constructor takes a word.
How do you populate a LinkedList of any type for example suppose I have a LinkedList of the Integer type, How do I fill it up with 10 integers?
I have just begin to understand collections in Java. I read about the differences between LinkedList and ArrayList but have several doubts on it. I have mentioned them below
1) Why retrieving in ArrayList is faster then LinkedList?. Since both have the get method how does performance differ?.
2) How does re-sizing happens internally in ArrayList when a item is added or removed?. How slow this is compared to the pointer re-shuffling in LinkedList when a item is added or removed?.
What is the starting index for linked list, 0 or 1. I know an array starts at 0 so wouldn't a linked list?
View Replies View RelatedI'm doing LinkedList at the moment and I'm having a bit of trouble with my assignment. The part I'm struggling with is remove an employee from a training course (as specified by their employee number),
what I'm confused about is iterating through the linked list to find the employee we're looking for. What I would do in this situation if I was using an array list is
for(Employee emp : myList) {
if(emp.getEmployeeNumber().equals(searchedNumber)) {
remove from training course..
break;
}
}
"Can only iterate over an array or an instance of java.lang.Iterable" is what it is telling me, and I can't figure out why/how its done differently for linked lists.
I can't figured out why it's keep giving me error when I tried to add i to the linkedlist. I tried changing it to other numbers but keep giving me nullExceptionPointer.
public static void subset(double[] weight, double[] value, int start) {
double sumWeights = 0;
for(int i = start; i<weight.length; i++){
if(sumWeights+weight[i]>L){
continue;
[Code] ....
What are the difference between hashmap, linkedlist and arraylist ... when they are used and why?
View Replies View RelatedI have a Queue class (containing a LinkedList plus a few other variables and stats for my project), which works fine with the standard LinkedList, but I'm trying to add my own code for MyLinkedList.
However, I keep getting a NullPointerException at my remove method.
public class MyLinkedList<T> {
Node head;
public MyLinkedList() {
head = null;
}
public class Node {
T contents;
Node nextNode;
[Code] ......
I am getting "Type safety: Unchecked cast from Object to LinkedList<EventData>" in eclipse for a piece of code stated below
public LinkedList<EventData> loadFromFile(File file) {
queue=new LinkedList<EventData>();
//Some piece of code
return (LinkedList<EventData>)queue.clone(); //--->getting warning here
}
I know that because clone() method is returning Object, hence compiler doesn't have type information that's why showing warning. I don't want to suppress this warning instead i want to fix it.
I have to create a class that has two fields. One called length and the other width. I have to make a method that returns the tract area. Similarly, I also have to make a method that indicates whether two objects have the same fields. Here is the code that I have assembled...so far
// create private fields to hold width and length
private double width;
private double length;
[Code].....
My problem is encountered when writing that equals method
if(length.equals(object.length) && width.equals(object.width))
I get an error saying HTML Code: cannot invoke equals(double) on the primitive type double. Meanwhile, I do see, to realize that when I change my fields to capital "Double." The problem disappears; however, in my class I have never dealt with a situation where I have to use capital d in double. In fact, I don't even know what's the difference between Double and double. I do know what double is but not the other one..
I have a JSP page that calls a Java method .. using GlassFish 4.0 it worked just fine, now I'm trying to run it on a new server with Tomcat 6.0 but it keeps giving me this error: "the function result must be used with a prefix when a default namespace is not specified"
Here's my JSP page:
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
......
<jsp:useBean id="diskUtilData" scope="request" class="newpackage.ResultPage" />
.....
<c:forEach var="celldata" items="${diskUtilData.result()}">
[Code].....
I am getting these errors with this code, I can not figure why this error is occuring.
what is the issue with this code?
Java Code: package ABC;
import java.util.ArrayList;
import java.util.Scanner;
public class GetInputFromUser {
private ArrayList<String> name = new ArrayList<String>();
[code]....
I am supposed to create a method that simulates a perfect shuffle of a given array of integers. According to the assignmment, this is what a perfect shuffle is:
This procedure is called a perfect shuffle if the interleaving alternates between the two half-decks.Unfortunately, the perfect shuffle comes nowhere near generating all possible deck permutations.In fact, eight shuffles of a 52-card deck return the deck to its original state!Consider the following perfect shuffle algorithm that starts with an array named cards that contains 52 cards and creates an array named shuffled.
Initialize shuffled to contain 52 empty elements.
Set k to 0.
For j = 0 to 25,
− Copy cards[j] to shuffled[k];
− Set k to k+2.
Set k to 1.
For j = 26 to 51,
− Copy cards[j] to shuffled[k];
− Set k to k+2.
This approach moves the first half of cards to the even index positions of shuffled, and it moves the second half of cards to the odd index positions of shuffled.The above algorithm shuffles 52 cards. If an odd number of cards is shuffled, the array shuffled has one more even-indexed position than odd-indexed positions. Therefore, the first loop must copy one more card than the second loop does. This requires rounding up when calculating the index of the middle of the deck. In other words, in the first loop j must go up to (cards.length + 1) / 2, exclusive, and in the second loop j most begin at (cards.length + 1) / 2.
i'm trying to exit the recursion of a void method but some funny things are happening before and after the return statement.
public static void main(String args[])
{
//code
rec(x,y);
System.out.println("HEllooooooo");}
public static void rec(int x,int y)
{
try
{
System.out.println(x+" "+y+" "+check);
if(x==fx && y==fy)
[code]....
I am trying to run the following code but getting the error above.
import java.io.*;
public class StringBuilder {
public StringBuilder() {
super();
}
public static void main(String args[]) {
// creates empty builder, capacity 16
StringBuilder sb = new StringBuilder();
// adds 9 character string at beginning
sb.append("Greetings");
}
}
I am trying to return an array and I keep getting a null error. The below class sets the material numbers into an array and should return that array if called :
public class Jobs {
private int[] materialsNumber;
//change to parts and create another class that gets the materials for the parts
public int[] job1() {
materialsNumber[0] = 11960120;
[Code] ....
I later try to call the method. The program executes but stops after I println "test in loop"
public class PurchaseOrdersToParts {
private Jobs job = new Jobs();
int[] getPartsForPurchaseOrder(BigDecimal purchaseOrder) {
System.out.println("inside getparts");
BigDecimal testNum = new BigDecimal(123.0);
[Code] ....
This is the method that is calling the method in the GenerateOrdersToParts class
private PurchaseOrdersToParts purchaseOrdersToParts = new PurchaseOrdersToParts();
@Inject
PoRepository poRepository;
public GenerateShopJobTickets() {
[Code] .....
I am writing a palindrome program. I don't understand what is wrong with my Main method. It is giving me error and error is "Can not find symbol in main method"
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class PalindromeA extends JFrame {
private JTextField inText;
private JTextField outText;
[Code] ....
So I built this comparator exactly the same way I built my others that are working.But the comparator for UserComparator is not being found for some reason.I will post my usercomparator class and JSP page.
<%@page import="tickets.UserComparator"%>
<%@page import="tickets.User"%>
<%@page import="tickets.ReporterTTComparator"%>
<%@page import="tickets.StatusTTComparator"%>
<%@page import="tickets.SystemTTComparator"%>
<%@page import="java.util.Collections"%>
<%@page import="java.util.ArrayList"%>
<%@page import="tickets.TroubleTicket"%>
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
[code]....
I'm trying to call the grade.processFile method from the main method but I'm getting this Error below. I'll post my code which includes the main method and the class underneath the error message:
Exception in thread "main" java.lang.NullPointerException
at java.io.FileInputStream.<init>(FileInputStream.jav a:130)
at java.util.Scanner.<init>(Scanner.java:611)
at MyGrades.processFile(MyGrades.java:49)
at myGradesMain.main(myGradesMain.java:19)
import java.util.Scanner;
import java.io.*;
[code]...
I am trying to create a Hangman program using Arrays. When trying to compile my code I get the following error: 50: error: no suitable method found
for setCharAt(int,String)
method StringBuffer.setCharAt(int,char) is not applicable
method AbstractStringBuilder.setCharAt(int,char) is not applicable
Here's the code:
import java.util.*;
import java.io.*;
public class hangman {
public static void main() throws IOException {
Scanner kb = new Scanner(System.in);
String filename;
[code]....
My code is giving me an error at the main method and it says that modifier 'static' is not allowed in constant variable declarations. every program that i searched for had the same code line but none had the problem i do.
package regularpolygon;
/**
*
* @author home1
*/
import java.lang.Math;
import java.text.*;
[code]...
Need to write two files but getting an expected exception error.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Scanner;
import java.io.FileWriter;
public class TestingPanel extends JPanel
[Code] ....
TestingPanel.java:49: error: unreported exception IOException; must be caught or declared to be thrown
FileWriter outputFileQuestions = new FileWriter("Test.txt");
^
TestingPanel.java:50: error: unreported exception IOException; must be caught or declared to be thrown
FileWriter outputFileAnswers = new FileWriter("Answers.txt");
[Code] ....
I am new to Java and trying to learn it.I wrote the following program but while creating the method nav i am getting errors.
Error:- void is an invalid type for the variable nav
import org.openqa.selenium.*;
import org.openqa.selenium.firefox.FirefoxDriver;
import java.util.*;
public class YahooHomepage {
private static WebDriver driver;
[Code] .....
I wrote this program to prompt user to enter his choice to do a i/o operation in a file. It shows error. How to clear the error. My code is:
import java.io.*;
import java.util.*;
class Files {
public static void main(String args[]) {
String n;
[Code] ....
error:
E:java>javac Files.java
Files.java:26: error: no suitable method found for write(String)
fos.write(n);
[Code] ....
The error I get when I execute my java file.
Exception in thread "main" java.lang.NullPointerExceptionat DogTestDrive.main(DogTestDrive.java:19)
Here is the source
class Dog {
int size;
String name;
void bark () {
if (size < 60) {
System.out.println("Woof woof");
[code]....
Some background: I'm reading "Head first Java 2nd edition" and I'm going through the examples which is showing me how to change the state of an object. The original code looks like the code below, however the previous chapter went over creating array's of an object, so I created an array of the object "Dog" and wanted to re-write it this way. To my understanding, it should work but it's giving me that error when I execute it. The error itself isn't very clear, if I could get a line number pointed to, that would work.
class Dog {
int size;
String name;
void bark() {
if (size > 60) {
System.out.println(“Wooof! Wooof!”);
} else if (size > 14) {
System.out.println(“Ruff! Ruff!”);
} else {
System.out.println(“Yip! Yip!”);
[code]....