I am trying to sort an ArrayList of objects with the comparator as I want to sort based on a certain value for each object. I understand I would need to override compareTo() in the objects class, is there any way I can get around also needing to override for all subclasses of the object?
View RepliesI read the document [URL] ....
But I am not able to get what is actual use of this in set ?
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 Relatedoverriding of the compare method.
Here's an example I found:
public class Someone {
String name;
int age;
ArrayList <Someone> listarr = new ArrayList <Someone>();
public Someone(String name1, int age1) {
name = name1;
age = age1;
[code]...
1. In the compare method, what happens when it returns one of the 0, -1, or 1? How does returning such values contribute to the sorting process? How does it take in information (like I know it does through the parameters, but how exactly)?
2. Why do we use the class name for the generics?
Something about implementing Comparator interface isn't very clear to me: overriding the compare method.
Like here for example:
//This sorts a list of objects holding information based on age: the name and the age of the person
public class Person {
String name;
int age;
public Person (String name, int age)
{
this.name = name;
this.age = age;
[Code] ....
What exactly is happening behind the scenes? I don't understand mostly the part where it returns a 0, a 1, or a -1. After it returns one of those values, what really happens next?
For the displaying of the list, is the method toString() being accessed to output the list in the System.out.println statement?
For the generics, why do we use Person?
If an array has been sorted using a comparator then why is it necessary to pass on that comparator to the binaryserach method. What I want to know is that how come the presence of a comparator reference affect the way the algorithm works?
View Replies View RelatedI have a java code that should sort an array of names based on the last name. e.g jane a, jane b, jane z, jane d should be jane a, jane b, jane d, jane z. I have the following code but for some reasons, the s1 in the comparator method is always null.
public class ShuffleName {
public static void sortNames(String[] names){
Arrays.sort( names, new Comparator<String>() {
public int compare( String s1, String s2 ) {
String s1last = s1.split("s+")[1];
String s2last = s2.split("s+")[1];
return s1last.compareTo(s2last);
[code]....
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.
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?
Is it possible to compare 100 objects using comparator interface in java?
View Replies View RelatedSo 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]....
The initial output of the texfile is this. NO ARRAYLIST OR COMPARATOR IS ALLOWED:
Steve Jobs 9 f 91
Bill Gates 6 m 90
James Gosling 3 m 100
James Gosling 3 f 100
Dennis Ritchie 5 m 94
Steve Jobs 9 m 95
Dennis Ritchie 5 f 100
Jeff Dean 7 m 100
Bill Gates 6 f 96
Jeff Dean 7 f 100
Sergey Brin 27 f 97
Sergey Brin 22 m 98
The collateExams method collates/sorts exam objects starting with the first 'm' (midterm) of the first object and immediately followed by the same person's 'f'(final). Only a SINGLE loop construct is allowed. The output from collateExams() should be the one below but my code is not working, i.e. collateExams method is not working. The output from collateExams() should be
Bill Gates 6 m 90
Bill Gates 6 f 96
James Gosling 3 m 100
James Gosling 3 f 100
Dennis Ritchie 5 m 94
Dennis Ritchie 5 f 100
Steve Jobs 9 m 95
Steve Jobs 9 f 91
Jeff Dean 7 m 100
Jeff Dean 7 f 100
Sergey Brin 22 m 98
Sergey Brin 27 f 97
I am getting [b]NullExceptions[/b] at
r[2*position[exams[i].getID()]+1] =
new Exam(r[i].getFirstName(), r[i].getLastName(),
r[i].getID(), r[i].getExamType(), r[i].getScore());
import java.io.*;
import java.util.*;
[Code] ....
Ok here are my 2 Classes
Both have Identical Fields
package com.Lists;
public class EmployeeOffice implements EmpInterface {
private double salary;
private String name;
private String postion;
private double hoursWorked;
[Code] .....
So if i wanna sort this Generic class using comaparator what do i do... I cant find an answer to this... I wanna sort them on the basis of salary what to do ...
So we have to ask the user to put in a string of letters, and bring those letters in as cars to where there is a storage area and an assembly area, and we have to sort them from there into the assembly area with the smallest (A) at the head. I think I set up my code pretty well, but when I run it, no matter what I put in it returns CBAo. Say I input KATE, it should return TKEA but instead CBAo or if I input JANICE it should return NJIECA but it just returns EDCBAo. Here's my code:
import java.util.Scanner;
import java.util.Stack;
public class carStacksDessart
{
public static void main(String[] args) {
Stack<Integer> storage = new Stack();
[Code] ....
I'm trying to create a method that takes a map and sorts it alphabetically. I think I have the logic correct but I'm getting errors when I run it:
private static void sortMapAlphabetically(
Map<String, String> termsAndDefinitions) {
Map<String, String> tempMap = new Map2<String, String>();
[Code].....
I have to sort out my ArrayList but cannot make it work. Here is
Java Code:
Collections.sort(this.users);
User poor = this.users.get(0);
User ritch = this.users.get((this.users.size()-1));
System.out.println("Poorest user has" + poor.getUsername() + poor.getBalance() );
System.out.println("Ritches user has " + ritch.getUsername() + poor.getBalance() + "
"); mh_sh_highlight_all('java');
The Collections.sort(this.users); does not work.
i am doing a code using JSTL to fire a query. everything come fine except the resule is not sorted as desired. i am putting the code below--
String sort_order=(String)request.getAttribute("sort_order");
request.setAttribute("sort_order",sort_order);
<sql:query var="viewQueryj" sql= "select USER_ID, PERMISSION_ID, USER_NAME from administrator order by ?">
<sql:param value="${sort_order}"/>
</sql:query>
now the resule is always sorted by USER_ID. if i want to sort it using USER_NAME i pass parameter from controller to this page in sort_oredr variable which comes fine but the result doesn't sort by name, only by id. if i hardcode USER_NAME in query then the result is as desired.
I need to sort a 2D array to look like this : [URL] ....
Here is the code that I have.
File 1:
import java.text.DecimalFormat;
public class Assignment1 {
public static void main(String[] args) {
String[][] rainArray
= {
{"January", "3.03"},
[Code] ....
The following code is supposed to generate random integers and sort array1 and array2 using two different sorting methods. array1 is to be sorted with a "selection sort" method and array2 is to be sorted with the built-in Arrays.sort() method. However, array1 is the one that has a problem. It does not appear to output any values at all for array size of 4000 or more, such as array1[10000]. The assignment is to generate random integers, sort and benchmark the speeds at which array1 and array2 can generate and sort ints at array1[1000] array2[1000] array1[10000] array2[10000] array1[100000] array2[100000]
/**
*
* The following is a sorting and benchmarking program to sort
* array1 and array2 with 1,000 , 10,000 and 100,000 array sizes.
* array1 uses selection sort from section 7.4 of the book
* and array2 uses the built in Arrays.sort() method.
[code]....
I cannot post the output because the amount of data seems to have crashed the two previous posts I made on this topic due to the size of the problem.
I am reading a file and sorting a list, and I cannot figure out why I am getting an error on line 15 that contains the following code
Collections.sort(sortedContributorList, new Contributor());
This is the error I keep getting:
The method sort(List<T>, Comparator<? super T>) in the type Collections is not applicable for the arguments (LinkedList<Contributor>, Contributor)
import java.util.*;
import java.io.*;
public class myhashTable {
public static LinkedList<Contributor> sortedContributorList = new LinkedList<Contributor>();
public myhashTable(){
[code]....
I have a code that is meant to read a file and organize all the names from least to greatest salaries. It also allows the user to enter a name to find from the file, and the program finds the name and displays it. I have two errors, and I will show the error in my code
View Replies View RelatedI'm very new to Java and ran into a problem. My results are not in order and I'm not sure what I'm doing wrong.
My results come out like this instead of being in order from lowest to highest: "77 99 44 55 22 88 11 0 66 33"
Here's what I have:
class ArrayIns {
private long[] a; // ref to array a
private int nElems; // number of data items
//--------------------------------------------------------------
public ArrayIns(int max) // constructor
{
a = new long[max]; // create the array
nElems = 0; // no items yet
[Code] .....
I'm getting this error:
The operator < is undefined for the argument type(s) java.util.ArrayList<FacebookUser>, java.util.ArrayList<FacebookUser>
For this:
class FriendsComparator implements Comparator<FacebookUser>
{
@Override
public int compare(FacebookUser o1, FacebookUser o2)
{
int returnValue = 0;
if (o1.friends < o2.friends)
returnValue = -1;
[Code] ....
Same as for the second if condition. How can I fix this exactly? What I'm doing is trying to sort Facebook users by the most to least amount of friends.
Here's the Driver:
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.Scanner;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
[Code] .....
I have made a node class and im trying to implement a sorting method. I must use a selection sort but with specific instructions: "Your method should not need to use the new operator since it is just moving nodes from one list to another( not creating new nodes)
this is my current implementation ..but i am instantiating new object..
public class NodeInt
{
private int data;
private NodeInt next = null;
public NodeInt(){}
//precondition:
//postcondition:
public NodeInt(int data, NodeInt next)
{
this.data = data;
this.next = next;
[code]....
edit: this is the part that worked but i had it commented out so i have the previous and current declared above but didnt copy.
I'm trying to sort 10 inputted numbers (double precision) using the Array.sort() method. I can get the 10 numbers inputted, but the output is ten 0.0s; now (and this how I know I am learning some things) I'm fairly certain that the variable number is not storing the numbers inputted by the user otherwise I wild be seeing the program work correctly.
So my question is why isn't number storing the inputs?
import javax.swing.JOptionPane;
import java.util.Arrays;
public class KrisFrench3 {
public static void main(String[] args) {
double[] number = new double[10];
for(int i = 1; i <= i; i++) {
[Code] .....
Write a method called isSorted that accepts an array of real numbers as a parameter and returns true if the list is in sorted (nondecreasing) order and false otherwise. For example, if arrays named list1 and list2 store {16.1, 12.3,22.2, 14.4} and {1.5, 4.3, 7.0, 19.5, 25.1, 46.2} respectively, the calls is Sorted(list1) and isSorted(list2)should return false and true respectively. Assume the array has at least one element. A one-element array is considered
to be sorted. public class thirfd {
public static void main(String[] args) {
double[] arr1 = {16.1, 12.3,22.2, 14.4};
double[] arr2 = {1.5, 0.3, 7.0, 19.5, 25.1, 46.2};
isSorted(arr2);
System.out.println(isSorted(arr2));
[code]...