I have big problem with mergesort in Java. I can't figure out why it do not works. I need write it on lists using Comparable. Here is piece of code:
Java Code:
class MergeSort{
Comparator _comparator;
List lista = new ArrayList<>();
List list_temp = new ArrayList<>();
MergeSort(Comparator comparator){
[Code] ....
I have tried everything, still no results. It's return list with random placed numbers.
We are supposed to create a MergeSort method without the using recursion. Most of the code is already completed, the only thing that I believe I need are two for loops (an inner and an outter) that will make calls to the merge method. I need implementing the sort method of the merge sort algorithm without recursion, where the length of the array is a power of 2. Keep merging adjacent regions whose size is a power of 2. For ex: lengths will be 1, 2, 4, 8, 16,.
public class MergeSorter {
public static void sort(int[] a) {
//for(int i = 1; i <= a.length; i++) the parameters for the for loop are wrong.
{
merge(0,0,1,a);
merge(1,1,2,a);
merge(2,2,3,a);
[Code]...
I am asked to create a code that if a user enters 1 it will use the object natural comparison form ('default') as written in CompareTo method.But if he chooses to enter something else then another comparison is used.Maybe I just need to use 2 diff comparators? but then what;s the point of defining something as 'default'....
View Replies View RelatedI have the following code that will make linked list and order its elements using self referential objects. but i have the following error:
incompatible types
required: ListNode<T#2>
found: ListNode<T#1>
where T#1,T#2 are type-variables:
T#1 extends Comparable declared in method <T#1>insertInOrder(T#1)
T#2 extends Comparable declared in class OrderedList
import java.util.*;
public class ListNode<T> {
ListNode<T> nextNode;
T data;
public ListNode(T item)
{
this(item, null);
[code]...
I have a task to create a Java OOP program, I have a class Team which requires a comparable and iterable interface, the only way I know how to do this is either:
public class Team implements Iterable <Mechanic>
or
public class Team implements Comparable <Mechanic>
How do I add both?
Which of the following classes uses Comparable and Comparator?
QueueTreeSetStackPriorityQueue
In the above question, what does 'uses' mean? Does it mean do above classes implement Comparable and Comparator?
I know that in order to compare any two elements stored in one of the above classes, we need to make the elements' class to implement one of these - either Comparable or Comparator.
Here is my code:
/*
* Implement the Comparable interface on objects of type Order.
* Compare orderId, then productId. The lesser orderId should come first. If the orderIds match, then the lesser productId should come first.
*/
@Override
public int compareTo(Order ord) {
// TODO Auto-generated method stub
if(orderId > ord.orderId){
return 1;
[Code] ....
Here is the output:
Actual: 0
Expected: -1
Actual: -1
Expected: -1
Actual: 1
Expected: 1
Actual: 1
Expected: 1
Actual: 0
Expected: 0
Actual: 0
Expected: 0
In short, the "Actual" is what my code produces and the "Expected" is what it is supposed to produce. As you can see, only the first one is mismatching... I'll admit, the comment section above the method is confusing and I wasn't exactly sure what it wants me to do, but I thought I figured it out. I just don't see how 5/6 of these tests can work and the 6th one not.
Why is it necessary to implement the comparable interface for primitive types and not for classes such as Integer, String etc . . . ?
View Replies View RelatedMy book defines this generic method
Java Code:
public static <E extends Comparable<E>> void sort(E[] list... mh_sh_highlight_all('java');
Comparable is an interface and from how i look at this piece of code is that I can only use a class that implements the Comparable interface; however, this is the context my book uses when explaining the following code
First, it specifies that E is a subtype of Comparable.
Second, it specifies that the elements to be compared are of the E type as well.
What does it mean when it says E is a subtype.
I was going through some lectures online and found that to compare or even swap, the use of comparable or comparator argument like
public static boolean less(Comparable v,Comparable w)
{
return v.compareTo(w)<0;
}
public static void swap(Comparable []a,int i,int j)
{
Comparable swap=a[i];
a[i]=a[j];
a[j]=swap;
}
I did not get the use of passing Comparable or Comparator to the function as parameters. Object as parameter could have been used too?
Below is the requirements and code. I am getting the error CODELAB ANALYSIS: LOGICAL ERROR(S)We think you might want to consider using: >
Hints:
-Correct solutions that use equals almost certainly also uses high
-Correct solutions that use equals almost certainly also uses low
Assume the existence of a Widget class that implements the Comparable interface and thus has a compareTo method that accepts an Object parameter and returns an int . Write an efficient static method , getWidgetMatch, that has two parameters . The first parameter is a reference to a Widget object . The second parameter is a potentially very large array of Widget objects that has been sorted in ascending order based on the Widget compareTo method . The getWidgetMatch searches for an element in the array that matches the first parameter on the basis of the equals method and returns true if found and false otherwise.
public static boolean getWidgetMatch(Widget a, Widget[] b){
int bot=0;
int top=b.length-1;
int x = 0;
int y=0;
while (bot >= top)
[code]....
I am working on an assignment that requires me to implement 2 methods (add() and remove()) and create an inner class (OrderedListNode). I must use data items of type Comparable. The items should be sorted.
I understand what needs to be done, but I am having a difficult time actually writing the code. I added the main method to check to see if my code works, and it doesn't seem like that is even being read.It compiles without error - it only gives a warning of unchecked or unsafe operations.
Code:
package dataStructures;
//This class functions as a linked list, but ensures items are stored in ascending order.
public class OrderedLinkedList {
//return value for unsuccessful searches
private static final OrderedListNode NOT_FOUND = null;
[code]...
Operator is undefined for argument type. Error is located at the end of the binary search method array[position] < key
import java.util.Arrays;
public class binarySearch {
public static <T extends Comparable<T>> int binarysearch(T key, T[] array) {
int start = 0;
int end = array.length - 1;
int position =-1;
while (start <= end && position == -1) {
[Code]....
How do you enforce any class which implements an interface should also implement comparable too? Say for instance you may have an interface
public interface Task
{ ... }
public class DoThis implements Task { ... }
public class DoThis1 implements Task { ... }
I want all of the classes which implements the interface Task to implement comparable too. Of course I can just say implements Task, Comparable. But is there something which we could do from interface level, i mean interface Task level?
My assignment was to create a priority queue for Airline Passengers. Here is what I have done so far:
//Driver
package priorityqueuestandby;
import java.util.NoSuchElementException;
import javax.swing.JOptionPane;
public class PriorityQueueStandBy {
public static void main(String[] args) {
[Code] .....
So the part that I cant figure out is:
When a standby passenger is to be enqueued into the priority queue, it must be done so that at the moment of each dequeue operation, the item at the head of the queue is the standby passenger with the longest longevity, and also so that passengers with the same longevity are dequeued in a first-come-first-served fashion.
he says that we need to "Make your program so that it extends Comparable and implements the compareTo() method properly..."
So I was looking at the Comparable class and I could't find a compareTo() method... I am not confident I know how extends works either. I am assuming I need a new class if I am going to be extending another class. Right now I am taking in longevity as a String and converting it to an int because my last ditch effort is going to be to set up a loop that will organize longevity into a/an circular array based on the size of the incoming integer.
public void myFunc(MyNode n, ArrayList<MyNode> path) {
boolean hasChildren = false;
path.add(n);
int index = path.indexOf(n);
ArrayList<MyNode> statefulPath = new ArrayList<MyNode>();
[Code] ....
I have similar code that I stepped through in a debugger. After running the code I found that it built the desired tree, in this case a root node H with left child L and right child P. I want list of lists to contain all paths from root to leaf. I expected [H, L] and [H, P]. I discovered that statefulPath is not stateful; after a recursive stack frame pops, statefulPath still contains n! But that stack frame just popped! I expected to see statefulPath be [H] in the debugger and it was [H, L]! So I later have a list [H,L,P] which I don't want. How do I make the statefulPath list I want for my algorithm?
List list1 = query1.list();
List list2 = query2.list();
for (Iterator itr = list1.iterator(); itr.hasNext();) {
Object[] row = (Object[]) itr.next();
}
I currently don't understand how the node's work.
private static class Node<AnyType>
{
private AnyType data;
private Node<AnyType> next;
public Node(AnyType data, Node<AnyType> next)
{
this.data = data;
this.next = next;
}
}
Why do I make private Node<AnyType> next;And why do I have an inner class of Node for a linked list?I had the same topic in C, but there it was somehow easier than in java. Because there you have pointers.
Write a Java function Sum2List that takes two lists L1 and L2 of the same size and returns list L that contains the sum of data inside the corresponding nodes of lists L1 and L2.
ex: L1 = {1,2,3}
L2 = {4,5,6}
L = {5,7,9}
I do not know how to iterate through two different lists >>
public LinkedList Sum2List(LinkedList l1, LinkedList l2){
LinkedList l3 = new LinkedList();
ListNode Current1 = L1.getFront();
ListNode Current2 = L2.getFront();
while(Current1 != null){
l3.Add(Current1.getItem() + Current2.getItem());
[Code] .....
This my attempt to write the code , but the dr. side that we have not to use the build in methods ( getNext()...etc)
in the function .
I have an XML sheet and my project is top retrieve the required elements from XML sheet. So my format of XML was like follows:
<Class>
<Employees>
<EMPLOYEE>
<ENum> Abc123</ENum>
<Ename> John<?Ename>
<EType>Mathematics</EType>
[Code] ....
I have used unmarshalling concept to retrieve the data elements... I have to check whether the elements satisfy few regulations when compared with data in Database. So, i thought of grouping the employees depending on EType. I have created a Map with linkedlist of employees. Say Map<String, LinkedList<Employe>>EmpMap=new Map<String, LinkedList<Employe>>();
I have already created a class named Employee which has all the setter and getter methods for employee.
Here am going to take Etype(Employee type) as key and linkedlist(list of employees of certain type) as value. How to iterate these linked lists and place them in my Map.
What is going on here in the main class is a zoo that requires information to be read from and saved to a .txt file. I have made three arrayLists for each .txt file, I am getting errors for illegal start to an expression
import java.io.*;
import java.util.*;
public class ColumbusZoo
{
public static void addHelper(ArrayList<DomesticAnimal> a){
Scanner s = new Scanner(System.in);
System.out.println("What species");
[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)
Why is this method throwing a null pointer exception when I call it from main?
I'm trying to submit an integer to indicate the number of nodes in a linked list to delete and then delete them headfirst.
public boolean delete(int x){
if (x > count || head == null){
return false;
}else{ while (x>0){
head = head.getPrevious();
[Code] ....
A Employee Class where i want to sort there lists one by there salary and one by there name individually as per the requirement ? How we do it?
View Replies View RelatedI am familiar with Java but new to JSP. I have a Java Servlet app where user actions are recorded in a SQL Server database amd I now need to quickly put together a JSP front end application to view user actions. I want two drop down boxes to filter the results that will be displayed in a list box. What I need is the first drop down list box to show unique user names that have logged in. I can interrogate the database with the following SQL;
"SELECT DISTINCT(USER_ID) FROM AUDIT_MESSAGE"
Then when a user is selected from the first drop down list box (perhaps some sort of on change event) a second drop down list box shows the logins times of the selected user. Again I can interrogate the database with the following SQL;
SELECT SESSION_ID, EventTIME FROM dbo.AUDIT_MESSAGE
WHERE OPERATION = 'loginResponse' AND RESULTS = 'OK'
AND USER_ID = 'firstdropdownlistselection'
Then finally when a login time is selected in the second drop down list box all events for the selected user while logged in with that login time are displayed in the list box.
I have two JComboBox the first contains a list of patients, the second a list of antibiotics I want to make a button when I chose an antibiotic and a patient they will be added in my database (sql server)
View Replies View Related