currently, I'm doing an assignment that deals with the ArrayList class.
at some point, I need to check of the id of the instructor and make sure that the instructor is not added twice to the ArrayList, so I made a for loop to go through all the id that has been registered and get the id and check if it exists already
the problem is when I use the method " .size()" in the loop, the JVM throws NullPointerException
and I don't know why.
==========================================================================
what I need to read is this:
\\name - id - dateOfBirth - gender - degree - speciality - city - availability
Amanda Smith, 102020, 320101200000, M, PhD, Software Engineering, NewYork, true
=======================================================================
this is the code:
public static void main(String[] args) {
/* NOTE: I HAVE A CLASS CALLED "UniversityMember" THAT IS A SUPERCLASS FOR "Instructor" CLASS */
//declare what I need
ArrayList<UniversityMember> membersList;
Scanner read = new Scanner("inputFile.txt");//the file contains the text above
//First: Split the line everytime the sign ", " shows
String[] line = read.nextLine().split(", ");
//Second: Assign each valuse to its correspondeding variable
String name = line[0];
String id = line[1];
long date = Long.parseLong(line[2]);
Date birthDate = new Date(date);
char gender = line[3].charAt(0);
String degree = line[4];
String specialization = line[5];
String address = line[6];
boolean availability = Boolean.parseBoolean(line[7]);
//check if the Id is registered already
for (int i = 0; i < membersList.size(); i++) { //ERROR OCCURE
if (membersList.get(i) == null) {
break;
}
if (membersList.get(i).id.equals(id)) {
System.out.println("The instructor is registered already, the ID is found in the system.");
System.exit(0);
}
}
//add and make a new object for the constructor
membersList.add(new Instructor(name, id, birthDate, gender, degree, specialization, address, availability));
System.out.println("The instructor is successfully added.");
}//end main
The problem is membersList doesn't exist when you call .size() on it
instead of
ArrayList<UniversityMember> membersList;
you need to initialize it
ArrayList<UniversityMember> membersList = new ArrayList<UniversityMember>();
You need to initialize the ArrayList.
Like that ArrayList membersList = new ArrayList();
After that, in the first size() returns 0 and not null. Remember all data structure must be initialize in java.
You haven't added anything to the membersList then asking for the size for something that has nothing in it.
Example of whats going on
String str;
for(int i = 0; i < str.length(); i++){
System.out.println("hey");
}
also you need to declare the array list like this
ArrayList<Method name> membersList = new ArrayList<Method name>();
also don't forget to import the ArrayList class
import java.util.ArrayList;
nvm I figured out that I haven't initialized my array ( ╥ω╥ )
I'll keep the question for others to be carefull
==================================================
The code after fixing it:
public static void main(String[] args) {
/* NOTE: I HAVE A CLASS CALLED "UniversityMember" THAT IS A SUPERCLASS FOR "Instructor" CLASS */
//declare what I need
ArrayList<UniversityMember> membersList;
Scanner read = new Scanner("inputFile.txt");//the file contains the text above
/* ===== FIXING THE ERROR ======*/
membersList = new ArrayList();
//First: Split the line everytime the sign ", " shows
String[] line = read.nextLine().split(", ");
//Second: Assign each valuse to its correspondeding variable
String name = line[0];
String id = line[1];
long date = Long.parseLong(line[2]);
Date birthDate = new Date(date);
char gender = line[3].charAt(0);
String degree = line[4];
String specialization = line[5];
String address = line[6];
boolean availability = Boolean.parseBoolean(line[7]);
//check if the Id is registered already
for (int i = 0; i < membersList.size(); i++) {
if (membersList.get(i) == null) {
break;
}
if (membersList.get(i).id.equals(id)) {
System.out.println("The instructor is registered already, the ID is found in the system.");
System.exit(0);
}
}
//add and make a new object for the constructor
membersList.add(new Instructor(name, id, birthDate, gender, degree, specialization, address, availability));
System.out.println("The instructor is successfully added.");
}//end main
Related
I doing a bigger school project (first part of basic objective programming in java - so not touched extended, polyphorism etc yet, thats next part), but run in to a small problem and tried for couple of days to find solution (thru books and internet). I constructed different ArrayLists in one class and different classes (at least two) should get access to them.
public class Customer
{
public void subMenuCustomer()
{
............code............
int subMenuCust;
ServiceLogic addCustomer = new ServiceLogic();
ServiceLogic listAllCustomers = new ServiceLogic();
while(true)
{
System.out.println("Please Choose your preference: ");
System.out.println("Create account, press \"1\": ");
System.out.println("Get list of clustomers, press \"2\": ");
System.out.println("Log out, press \"0\": ";
subMenuCust = input.nextInt();
switch(subMenuCust)
{
case 1 ://Call method createCustomer in class ServiceTech to add new customers
addCustomer.createCustomer(name, lastname, ssNo);
break;
case 3
listAllCustomers.getCustomer();
............more code..............
}
}
When user has added details (social secuity number, name and lastname) it is stored in seperate ArrayList. These three ArrayList are added(merge/concat) together to a fourth ArayList, listCustomer , so that all elements from the three ArrayList end up in same index [101 -54 Clark Kent, 242-42 Linus Thorvalds, ...].
import java.util.ArrayList;
import java.util.Scanner;
public class ServiceLogic
{
//Create new ArrayLists of Strings
private ArrayList<String> listSSNoCustomers = new ArrayList<>();
private ArrayList<String> listNameCustomers = new ArrayList<>();
private ArrayList<String> listLastnameCustomers = new ArrayList<>();
private ArrayList<String> listCustomers;
Scanner input = new Scanner(System.in);
public boolean createCustomer(String name, String lastname, String ssNo) //
{
System.out.println("Write social security number; ");
ssNo = input.next();
//loop to check that it is a uniq social security number
for(String ssNumber : listSSNoCustomers)
{
if (ssNumber.equals(ssNo))
{
System.out.println("This customer already exist. Must be uniq social security number.");
return true;
}
}
//If social security number is not on list, add it
//and continue add first name and surname
listSSNoCustomers.add(ssNo);
System.out.println(ssNo);
System.out.println("Write firstname; ");
name = input.next();
listNameCustomers.add(name);
System.out.println(name);
System.out.println("Write lastnamame; ");
surname = input.next();
listSurnameCustomers.add(lastname);
System.out.println(lastname);
return false;
}
public void setListCustomer(ArrayList<String> listCustomers)
{
this.listCustomers = listCustomers;
}
public ArrayList<String> getCustomer()
{
//ArrayList<String> listCustomers = new ArrayList<>();
for(int i = 0; i <listSSNoCustomers.size(); i++)
{
listCustomers.add(listSSNoCustomers.get(i) + " " + listNameCustomers.get(i) + " " + listFirstnameCustomers.get(i));
}
System.out.println("customer" + listCustomers);
return listCustomers;
}
}
According to the specification we got, when user want to see list of all customer the outputs should be in format [666-66 Bruce Wayne, 242-42 Linus Thorvalds, ...].
When user (staff) choose to enter details in class Customer ( Case 1 ) it works and elements get stored in the Arraylists for social security numbers, name and lastname (have checked that) .
The problem: when I run I can add customers, but when I try to get a list of customer the output: [] . I tried different solution, but same output only empty between the brackets.
So the question, how do I get ouput to work when user choose case 2 to get a list of all cutomers?
I have a txt document where each line is an independent message. This may include name, date of birth, address, etc. In addition to the address, all other information is in a row. Their order is not fixed. Name and birthday must be available, other information may not be available. If there is no name or birthday, this person should be ignored. Different people use blank lines to distinguish them. I want to read this information and put them in the arraylist, but I have no idea how to write the code.
My initial idea was to use a loop to read the content and store it, and if there was a blank line, start saving another content. But how to implement the code specifically I have no idea.
public class InforProcessor {
private File recordFile;
private File instructionFile;
private File outputFile;
private InforList inforlist;
public InforProcessor(String[]s)
{
recordFile = new File(s[0]);
instructionFile = new File(s[1]);
outputFile = new File(s[2]);
inforlist = new InforList();
}
}
This is my existing code, I want to read the contents of the recordFile and write to the arraylist.
Input file is like：
name john
birthday 11-11-2015
Address 11 Harry St, montain, TRY
birthday 12-25-2017
name peter
Postcode 2005
name jane
birthday 25-19-1998
Address 25 jeoje St, Sky, FLY
Postcode 1998
name geoge
The output information or useful information should be:
name john
birthday 11-11-2015
Address 11 Harry St, montain, TRY
birthday 12-25-2017
name peter
Postcode 2005
name jane
birthday 25-19-1998
Address 25 jeoje St, Sky, FLY
The last information should be delete because it do not have birthday.
First,you need to read all line from file,and every message splited by empty line.
Second,iterate over the message and check the messag is valid or not,if the message is valid then add the message to list.
private static List<String> filterFile(final String input) throws Exception {
List<String> result = new ArrayList<>();
List<String> lines = FileUtils.readLines(new File(input), "UTF-8");
System.out.println(lines.size());
int begin = 0;
int end = 0;
for (; end < lines.size(); end++) {
if (Strings.isNullOrEmpty(lines.get(end))) {
if (isValidInfo(lines, begin, end)) {
result.addAll(lines.subList(begin, end + 1));
}
begin = end + 1;
}
}
return result;
}
if message has name and birthday,the message is we want.
private static boolean isValidInfo(List<String> infos, int begin, int end) {
int counts = 0;
for (int i = begin; i < end; i++) {
String line = infos.get(i);
if (line.startsWith("name")) {
counts++;
}
if (line.startsWith("birthday")) {
counts++;
}
}
return counts == 2;
}
The overall project is creating a system manager for airports. It keeps track of airports, flights, seating sections, seats and other relevent info for each of those catagories. The initial system is set up by importing from a file that's formatted a certain way. I'm having problems parsing the file properly to set up the initial system. the data is parsed from the file and used as method parameters to create the objects: Airport, Airline, Flight, FlightSection, and Seat.
the formatting is:
[list-of-airport-codes] {list-of-airlines}
list-of-airport-codes ::= comma-separated strings
list-of-airlines ::= airline-name1[flightinfo-list1], airline-name2[flightinfo-list2], airlinename3[flightinfo-list3], …
flightinfo-list ::= flightID1|flightdate1|originAirportCode1|destinationAirportCode1[flightsectionlist1], flightID2|flightdate2|originAirportCode2|destinationAirportCode2[flightsection-list2], …
flightdate ::= year, month, day-of-month, hours, minutes
flightsection-list ::= sectionclass: seat-price: layout: number-of-rows, …
sectionclass ::= F, B, E (for first class, business class, economy class)
layout ::= S, M, W (different known seating layouts)
example:
[DEN,NYC,SEA,LAX]{AMER[AA1|2018,10,8,16,30|DEN|LAX[E:200:S:4,F:500:S:2],
AA2|2018,8,9,7,30|LAX|DEN[E:200:S:5,F:500:S:3], …], UNTD[UA21|2018,11,8,12,30|NYC|SEA[E:300:S:6,F:800:S:3], UA12|2018,8,9,7,30|SEA|DEN[B:700:S:5, F:1200:S:2], …], FRONT[…], USAIR[…]}
I tried brute forcing it using a combination of delimiters and while loops. The code successfully creates the Airports, first Airline and Flighsections, but when it gets to creating the second airline it crashes, because i'm not looping properly, and having a hard time getting it right. My code for it as of now, is a mess, and if you're willing to look at it, I would appreciate any constructive input. My question is what would be a better way to approach this? A different design approach? Maybe a smarter way to use the delimiters?
Thanks in advance for your help!!
here's what i've tried.
private void readFile(File file){
System.out.println("reading file");
Scanner tempScan;
String result;
String temp = "";
scan.useDelimiter("\\[|\\{");
try{
// AIRPORTS
result = scan.next();
tempScan = new Scanner(result);
tempScan.useDelimiter(",|\\]");
while(tempScan.hasNext()){
temp = tempScan.next();
sysMan.createAirport(temp);
}
tempScan.close();
/* AIRLINE
* FLIGHT
* FLIGHTSECTION
*/
do{
// AIRLINE (loop<flight & fsection>)
result = scan.next();
sysMan.createAirline(result);
// FLIGHT
result = scan.next();
tempScan = new Scanner(result);
do{
tempScan.useDelimiter(",|\\|");
ArrayList flightInfo = new ArrayList();
while(tempScan.hasNext()){
if(tempScan.hasNextInt()){
flightInfo.add(tempScan.nextInt());
} else {
flightInfo.add(tempScan.next());
}
}
tempScan.close();
sysMan.createFlight(sysMan.getLastAddedAirline(),(String)flightInfo.get(0), (int)flightInfo.get(1), (int)flightInfo.get(2), (int)flightInfo.get(3), (int)flightInfo.get(4), (int)flightInfo.get(5), (String)flightInfo.get(6), (String)flightInfo.get(7));
// FLIGHTSECTION (loop<itself>)
result = scan.next();
tempScan = new Scanner(result);
tempScan.useDelimiter(",|:|\\]");
ArrayList sectInfo = new ArrayList();
int i = 1;
while(!temp.contains("|")){
if(tempScan.hasNextInt()){
sectInfo.add(tempScan.nextInt());
} else {
temp = tempScan.next();
if(temp.equals(""))
break;
char c = temp.charAt(0);
sectInfo.add(c);
}
if(i == 4){
sysMan.createSection(sysMan.getLastAddedAirline(), sysMan.getLastAddedFlightID(), (char)sectInfo.get(0), (int)sectInfo.get(1), (char)sectInfo.get(2), (int)sectInfo.get(3));
i = 1;
sectInfo = null;
sectInfo = new ArrayList();
continue;
}
i++;
}
}while(!temp.equals("\\s+"));
}while(!temp.contains("\\s+"));
}catch(NullPointerException e){
System.err.println(e);
}
}
I'd rather chunk it down by regexp mathing the outer bounds, have a look, I took it a couple of levels broken.
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Tokeni {
static String yolo = "[DEN,NYC,SEA,LAX]{AMER["
+ "AA1|2018,10,8,16,30|DEN|LAX[E:200:S:4,F:500:S:2],"
+ "AA2|2018,8,9,7,30|LAX|DEN[E:200:S:5,F:500:S:3]],"
+ "UNTD[UA21|2018,11,8,12,30|NYC|SEA[E:300:S:6,F:800:S:3],"
+ "UA12|2018,8,9,7,30|SEA|DEN[B:700:S:5, F:1200:S:2]]}";
public static void main(String[] args) {
Matcher airportCodesMatcher = Pattern.compile("\\[(.*?)\\]").matcher(yolo);
airportCodesMatcher.find();
String[] airportCodes = airportCodesMatcher.group(1).split(",");
Matcher airLinesMatcher = Pattern.compile("\\{(.*?)\\}").matcher(yolo);
airLinesMatcher.find();
String airLinesStr = airLinesMatcher.group(1);
System.out.println(airLinesStr);
Pattern airLinePattern = Pattern.compile("\\D+\\[(.*?)\\]\\]");
Matcher airLineMatcher = airLinePattern.matcher(airLinesStr);
while( airLineMatcher.find() ) {
String airLineStr = airLineMatcher.group(0).trim();
if(airLineStr.startsWith(",")) {
airLineStr = airLineStr.substring(1, airLineStr.length()).trim();
}
System.out.println(airLineStr);
Matcher airLineNameMatcher = Pattern.compile("[A-Z]+").matcher(airLineStr);
airLineNameMatcher.find();
String airLineName = airLineNameMatcher.group(0).trim();
System.out.println(airLineName);
airLineStr = airLineStr.substring(airLineStr.indexOf("[")+1, airLineStr.length());
Matcher airLineInfoMatcher = Pattern.compile("\\D+(.*?)\\]").matcher(airLineStr);
while(airLineInfoMatcher.find()) {
String airLineInfoStr = airLineInfoMatcher.group(0).trim();
if(airLineInfoStr.startsWith(",")) {
airLineInfoStr = airLineInfoStr.substring(1, airLineInfoStr.length()).trim();
}
System.out.println(airLineInfoStr);
}
}
}
}
I am working on a project where I have been given a text file and I have to add up the points for each team and printout the top 5 teams.
The text file looks like this:
FRAMae Berenice MEITE 455.455<br>
CHNKexin ZHANG 454.584<br>
UKRNatalia POPOVA 453.443<br>
GERNathalie WEINZIERL 452.162<br>
RUSEvgeny PLYUSHCHENKO 191.399<br>
CANPatrick CHAN 189.718<br>
CHNHan YAN 185.527<br>
CHNCheng & Hao 271.018<br>
ITAStefania & Ondrej 270.317<br>
USAMarissa & Simon 264.256<br>
GERMaylin & Daniel 260.825<br>
FRAFlorent AMODIO 179.936<br>
GERPeter LIEBERS 179.615<br>
JPNYuzuru HANYU 197.9810<br>
USAJeremy ABBOTT 165.654<br>
UKRYakov GODOROZHA 160.513<br>
GBRMatthew PARR 157.402<br>
ITAPaul Bonifacio PARKINSON 153.941<br>
RUSTatiana & Maxim 283.7910<br>
CANMeagan & Eric 273.109<br>
FRAVanessa & Morgan 257.454<br>
JPNNarumi & Ryuichi 246.563<br>
JPNCathy & Chris 352.003<br>
UKRSiobhan & Dmitri 349.192<br>
CHNXintong &Xun 347.881<br>
RUSYulia LIPNITSKAYA 472.9010<br>
ITACarolina KOSTNER 470.849<br>
JPNMao ASADA 464.078<br>
UKRJulia & Yuri 246.342<br>
GBRStacey & David 244.701<br>
USAMeryl &Charlie 375.9810<br>
CANTessa & Scott 372.989<br>
RUSEkaterina & Dmitri 370.278<br>
FRANathalie & Fabian 369.157<br>
ITAAnna & Luca 364.926<br>
GERNelli & Alexander 358.045<br>
GBRPenny & Nicholas 352.934<br>
USAAshley WAGNER 463.107<br>
CANKaetlyn OSMOND 462.546<br>
GBRJenna MCCORKELL 450.091<br>
The first three letters represent the team.
the rest of the text is the the competitors name.
The last digit is the score the competitor recived.
Code so far:
import java.util.Arrays;
public class project2 {
public static void main(String[] args) {
// TODO Auto-generated method stub
String[] array = new String[41];
String[] info = new String[41];
String[] stats = new String[41];
String[] team = new String[41];
//.txt file location
FileInput fileIn = new FileInput();
fileIn.openFile("C:\\Users\\O\\Desktop\\turn in\\team.txt");
// txt file to array
int i = 0;
String line = fileIn.readLine();
array[i] = line;
i++;
while (line != null) {
line = fileIn.readLine();
array[i] = line;
i++;
}
//Splitting up Info/team/score into seprate arrays
for (int j = 0; j < 40; j++) {
team[j] = array[j].substring(0, 3).trim();
info[j] = array[j].substring(3, 30).trim();
stats[j] = array[j].substring(36).trim();
}
// Random stuff i have been trying
System.out.println(team[1]);
System.out.println(info[1]);
System.out.println(stats[1]);
MyObject ob = new MyObject();
ob.setText(info[0]);
ob.setNumber(7, 23);
ob.setNumber(3, 456);
System.out.println("Text is " + ob.getText() + " and number 3 is " + ob.getNumber(7));
}
}
I'm pretty much stuck at this point because I am not sure how to add each teams score together.
This looks like homework... First of all you need to examine how you are parsing the strings in the file.
You're saying: the first 3 characters are the country, which looks correct, but then you set the info to the 4th through the 30th characters, which isn't correct. You need to dynamically figure out where that ends and the score begins. There is a space between the "info" and the "stats," knowing that you could use String's indexOf function. (http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#indexOf(int))
Have a look at Maps.
A map is a collection that allows you to get data associated with a key in a very short time.
You can create a Map where the key is a country name, with value being the total points.
example:
Map<String,Integer> totalScore = new HashMap<>();
if (totalScore.containsKey("COUNTRYNAME"))
totalScore.put("COUNTRYNAME", totalScore.get("COUNTRYNAME") + playerScore)
else
totalScore.put("COUNTRYNAME",0)
This will add to the country score if the score exists, otherwise it will create a new totalScore for a country initialized to 0.
Not tested, but should give you some ideas:
public static void main(String... args)
throws Exception {
class Structure implements Comparable<Structure> {
private String team;
private String name;
private Double score;
public Structure(String team, String name, Double score) {
this.team = team;
this.name = name;
this.score = score;
}
public String getTeam() {
return team;
}
public String getName() {
return name;
}
public Double getScore() {
return score;
}
#Override
public int compareTo(Structure o) {
return this.score.compareTo(o.score);
}
}
File file = new File("path to your file");
List<String> lines = Files.readAllLines(Paths.get(file.toURI()), StandardCharsets.UTF_8);
Pattern p = Pattern.compile("(\\d+(?:\\.\\d+))");
List<Structure> structures = new ArrayList<Structure>();
for (String line : lines) {
Matcher m = p.matcher(line);
while (m.find()) {
String number = m.group(1);
String text = line.substring(0, line.indexOf(number) - 1);
double d = Double.parseDouble(number);
String team = text.substring(0, 3);
String name = text.substring(3, text.length());
structures.add(new Structure(team, name, d));
}
}
Collections.sort(structures);
List<Structure> topFive = structures.subList(0, 5);
for (Structure structure : topFive) {
System.out.println("Team: " + structure.getTeam());
System.out.println("Name: " + structure.getName());
System.out.println("Score: " + structure.getScore());
}
}
Just remove <br> from your file.
Loading file into memory
Your string splitting logic looks fine.
Create a class like PlayerData. Create one instance of that class for each row and set all the three fields into that using setters.
Keep adding the PlayerData objects into an array list.
Accumulating
Loop through the arraylist and accumulate the team scores into a hashmap. Create a Map to accumulate the team scores by mapping teamCode to totalScore.
Always store row data in a custom object for each row. String[] for each column is not a good way of holding data in general.
Take a look in File Utils. After that you can extract the content from last space character using String Utils e removing the <br> using it as a key for a TreeMap. Than you can have your itens ordered.
List<String> lines = FileUtils.readLines(yourFile);
Map<String, String> ordered = new TreeMap<>();
for (String s : lines) {
String[] split = s.split(" ");
String name = split[0].trim();
String rate = splt[1].trim().substring(0, key.length - 4);
ordered.put(rate, name);
}
Collection<String> rates = ordered.values(); //names ordered by rate
Of course that you need to adjust the snippet.
I am have trouble creating an array or object(with multiple fields) and sending it to an array-list. Any help would be greatly appreciated. I have spent hours looking through every video on YouTube with the words object and array-list in them and have been unable to find much help.
The program needs to prompt the user to pick a option (1. AddItem) then prompt the user for the name and format (dvd, vhs) and save multiple objects with these variables in an array-list. I either keep having the location where it is saved in memory returned to me or instead of multiple objects one large object is created.
Library:
import java.util.Scanner;
import java.util.ArrayList;
public class Library {
static ArrayList<Object> items = new ArrayList<Object>();
static int menuOption;
static Scanner scan = new Scanner(System.in);
public static void main(String args[]) {
String title, format;
boolean right = false;
do{
displayMenu();
if (menuOption == 1){
System.out.println("Enter Title: ");
title = scan.next();
System.out.println("Enter format: ");
format = scan.next();
addNewItem(title, format);
} else {System.out.println(items);
}
} while (!right);
}
static int displayMenu(){
System.out.println("Menu: ");
System.out.println("1. Add New Item");
menuOption = scan.nextInt();
return menuOption;
}
static void addNewItem(String title, String format){
MediaItem b = new MediaItem();
b.setTitle(title);
b.setFormat(format);
items.add(b);
}
}
MediaItem:
public class MediaItem {
String title;
String format;
MediaItem(){
title = null;
format = null
}
MediaItem(String title, String format){
title = new String();
format = new String();
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getFormat() {
return format;
}
public void setFormat(String format) {
this.format = format;
}
}
The program will run if you:
1 - Change the line
static ArrayList<Object> items = new ArrayList<Object>();
to
static ArrayList<MediaItem> items = new ArrayList<MediaItem>();
2 - Change the line
System.out.println( items );
to
for ( MediaItem mi : items )
{
System.out.println( mi.getTitle() + ", " + mi.getFormat() );
}
3 - Insert a ";" at the end of the line
format = null
I did it here and it worked.
I either keep having the location where it is saved in memory returned to me
I am guessing you ran into this when you tried to either use System.out.println() to print a MediaItem, or you otherwise tried to automatically convert an object to a string. Whatever approach you took when you were seeing the memory addresses is probably the right way to do it, your problem was only in your displaying of the data.
Consider:
MediaItem item = ...;
System.out.println(item);
By default, Java doesn't know how to convert arbitrary objects to strings when you do stuff like that, and so it just spits out the class name and memory address. You either need to print the fields separately (e.g. Java knows how to display a String already), like:
System.out.println("Title: " + item.getTitle() + " Format: " + item.getFormat());
Or you can override toString() (declared in Object) to provide a custom string conversion:
class MediaItem {
...
#Override public String toString () {
return "Title: " + title + " Format: " + format;
}
}
And then you can print it directly:
System.out.println(item);
It is the default base implementation of Object.toString() that produces those strings with the memory address in them.
Based on your description, I'm guessing you had a roughly working implementation but ran into this issue and ended up changing around (and breaking) a bunch of other unrelated things to try and fix it.