Develop Reference

Is there a way i can add multiple variables to one object?

So I've been given the method below and I'm not allowed to change it. What I need is it to create a couple of objects with the variables below but keeps coming up with an error that says "The constructor menu(int, String, String) is undefined." Am I doing something wrong?
import java.util.Scanner;
import java.util.*;
public class menu {
private static void addNewStudent()
{
Scanner scanner = new Scanner(System.in);
System.out.println("Please enter the correct details below");
System.out.println("ID: ");
int userId = scanner.nextInt();
System.out.println("First name: ");
String userFirst = scanner.next();
System.out.println("Last name: ");
String userLast = scanner.next();
System.out.println("English assignment 1 mark: ");
int english1 = scanner.nextInt();
System.out.println("English assignment 2 mark: ");
int english2 = scanner.nextInt();
System.out.println("English assignment 3 mark: ");
int english3 = scanner.nextInt();
System.out.println("Math assignment 1 mark: ");
int math1 = scanner.nextInt();
System.out.println("Math assignment 2 mark: ");
int math2 = scanner.nextInt();;
System.out.println("Math assignment 3 mark: ");
int math3 = scanner.nextInt();
menu userStudentObj = new menu(userId, userFirst, userLast);
menu userEnglishObj = new menu(english1, english2, english3);
menu userMathObj = new menu(math1, math2, math3);
// Asks the user for the student information (ID, First, Last, Assignments)
// Then creates the appropriate objects and adds the students to the student list
I would expect to have created 3 new object that contain the user input variables within the objects if that makes sense.

The main problem is that you didn't specify any non default constructor, to create objects so compiler have no ideas what do you want to create if object is not specified for that. But there is another problem. Your object is designed in not the best way. So if you want to handle it correctly you could change your class design so you handle it in right way.
For example you could make it a bit different, like in this example (it's not perfect, it still can be more separate and better designed):
class User {
int userId;
String userFirstName;
String userSecondName;
private ArrayList<Integer> mathSums = new ArrayList<>();
private ArrayList<Integer> englishSums = new ArrayList<>();
User(int userId, String userFirstName, String userSecondName) {
this.userId = userId;
this.userFirstName = userFirstName;
this.userSecondName = userSecondName;
}
public void addMathSums(int mathSums) {
this.mathSums.add(mathSums);
}
public void addEnglishSums(int englishSums) {
this.englishSums.add(englishSums);
}
}
So by the help of this class you could change the way, how you define and set the values for your object and it would look like that:
1) You define constructor with arguments so you're able to use it for object creation:
User user = new User(userId, userFirst, userLast);
2) Then you can add sums into ArrayLists that are member variables (fields) in User class:
user.addMathSums(math1);
user.addMathSums(math2);
user.addMathSums(math3);
user.addEnglishSums(english1);
user.addEnglishSums(english2);
user.addEnglishSums(english3);
It could be performed in different ways using arrays, lists or other data structure, but you really need to pay attention for your class design. More time you spend on designing object less modifications you will need later.
3) You probably want to interact with this object so you need to get a reference for it somehow. You could change the method signature so you will "return" created object after you finish your input. So you need to make some changes:
On the method change the signature return type to User:
private static User addNewStudent() { ... }
Then add return for that and return created user:
private static User addNewStudent() {
/* code */
User user = new User(userId, userFirst, userLast);
/* add sums */
return user;
}
4) Use this method in your main():
public static void main(String[] args) {
User createdUser = User.addNewStudent();
}

Storing data in an Array and outputting that data

I am working on a program that stores data in an Array from the user and outputs that data.
For example:
An input:
Happy HAPPY#foo.com
The output:
NAME: Happy
EMAIL: HAPPY#foo.com
I was hoping someone could look at what I've got so far and give me a pointer on how to continue. I know I have to use the scanner class and scan.nextLine, I'm not sure what comes next. I understand I don't have much, I'm not looking for someone to complete this, but maybe someone who can give me some pointers or point me in the right direction. I believe I have the correct base to my program.
My Code So Far:
import java.util.ArrayList;
import java.util.Scanner;
public class Program5 {
void loadContacts()
{
Scanner scan = new Scanner(System.in);
System.out.println(scan.nextLine());
scan.close();
}
void printContacts()
{
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Program5 program5 = new Program5();
program5.loadContacts();
program5.printContacts();
}
}

Better name the class "person" or like this, but nevermind for the explanation :
public class Program5 {
private String name;
private String mail;
public Program5(){}
void loadContacts(){
Scanner scan = new Scanner(System.in);
System.out.println("Please enter a name and a mail like this : name email#email.com (separate with ' ')");
String[] line = scan.nextLine().split(" ");
while(line.length!=2){
System.out.println("Again, enter a name and a mail like this : name email#email.com (separate with ' ')");
line = scan.nextLine().split("/");
}
this.setName(line[0]);
this.setMail(line[1]);
scan.close();
}
void printContacts() {
System.out.println("NAME : "+this.name+"\nEMAIL : "+this.mail);
}
public static void main(String[] args) {
Program5 program5 = new Program5();
program5.loadContacts();
program5.printContacts();
}
public void setName(String name) {
this.name = name;
}
public void setMail(String mail) {
this.mail = mail;
}
}
In the loadyou ask the user, check it he enter 2 element separate by '/' and if yes store them as attributes to be able to get them in another method ;)

You should have a global varible to store the name and the email. Try adding these lines on the top of the code. after public class Program5 {.
private String Name, Email;
The you must assing this values to void loadContacts(). Spliting the string you read.
void loadContacts()
{
Scanner scan = new Scanner(System.in);
String input = scan.nextLine();
String arr[] = input.split("\\s+");
Name = arr[0];
Email = arr[1];
scan.close();
}
And finally on void printContacts().
void printContacts()
{
System.out.println("NAME: " + Name + "\nEMAIL: " + Email);
}
Here is the code runnig: http://ideone.com/mjyfHK

You can do a variety of things.
You can make loadContacts() and printContacts() static methods, and also change loadContacts() so that it returns an Array or 2D array or however you choose to represent a name-email pair. Then change printContacts()` to take in that type and iterate through that Array to print out each name/email pair. This solution is a bit more work but you won't have to create an object of the same class within the main method of that class.
or
You can keep your method as they are and instead create a new field for the program class, called contacts and it would be of the type that you choose for representing name/email pairs. You would add items to contacts in loadContacts() and iterate through it in printContacts(). Then you don't have to change anything in your main method.

Java - Calling private arraylist from class [duplicate]

This question already has answers here:
Is it possible in Java to access private fields via reflection [duplicate]
(3 answers)
Closed 7 years ago.
My template opens with a menu of options and the user inputs something between 1-3 to select one of the three options.
When the user chooses option 1, it asks them to input a number teamNumber. One must instantiate the class Team, then it writes it to an arraylist.
If there is at least one number in numberList, the user can select option 2. It asks them to input any of the numbers from the arraylist and searches it. If the number they input is found, then you input a String teamMemberFirstName and a char firstInitialLastName. Then it will write the input to a private arraylist located in another class TeamMember.
Once they have input the info in option 1 and 2, they can choose option 3. It allows you to print the list of inputted names based on which team number you put them on.
I am not sure how, in option 3, to call the private arraylist from the TeamMember class teamList. Any guidance on how to proceed with this step? My code is below.
Main class:
public class Main {
public static void main(String[] args) {
int choosing;
Scanner scan = new Scanner(System.in);
String input;
int teamNumber;
boolean stayInLoop;
ArrayList<Team> numberList = new ArrayList<Team>();
do {
stayInLoop = true;
System.out.println("1. Add a new team");
System.out.println("2. Add a new team member");
System.out.println("3. View teams");
input = scan.nextLine();
if (input.equals("1")) {
System.out.println("Enter a team number:");
teamNumber = scan.nextInt();
scan.nextLine();
Team addTeam = new Team(teamNumber);
numberList.add(addTeam);
}
if (input.equals("2")){
boolean foundIt = false;
boolean valid = true;
System.out.println("Team number:");
teamNumber = scan.nextInt();
scan.nextLine();
for (int a = 0; a < numberList.size() && foundIt == false; a++){
Team addTeam = numberList.get(a);
if (addTeam.findTeam() == teamNumber) {
foundIt = true;
System.out.println("Enter first name of team member:");
String teamMemberFirstName = scan.nextLine();
System.out.println("Enter first initial of last name:");
char firstInitialLastName = scan.nextLine().charAt(0);
TeamMember inputTeamMember = new TeamMember(teamMemberFirstName, firstInitialLastName);
inputTeamMember.addMember(inputTeamMember, valid = true);
System.out.println("Success!");
}
}
if (foundIt == false) {
System.out.println("Try again.");
}
}
if (input.equals("3")){
for (int a = 0; a < numberList.size(); a++) {
Team addTeam = numberList.get(a);
//Not sure what to put where there are ????'s - I tried a few ideas and stuff I found online, but nothing worked
//I assume I call the method/class here????
System.out.println("Team: " + addTeam.findTeam() + " Members: " +
"I will put the member called from the arraylist here????");
}
}
}while (stayInLoop == true;)
}}
TeamMember class:
public class TeamMember {
private final String teamMemberFirstName;
private final char firstInitialLastName;
private ArrayList<TeamMember> teamList = new ArrayList<>();
public TeamMember(String teamMemberFirstName, char firstInitialLastName) {
this.teamMemberFirstName = teamMemberFirstName;
this.firstInitialLastName = firstInitialLastName;
}
public int addMember(TeamMember member, boolean valid) {
valid = teamList.add(member);
return teamList.size();
}
}

You cannot directly access private fields from other classes. Either move your list to the Team class or create a getter to retrieve the list.

In a public class, you can return a private object in a public method. This seems like the easiest way in this project. Add a new method to your TeamMember class, and have it return teamList:
//inside your TeamMember class, anywhere after you assign the private variable
public static ArrayList show(){
//the static keyword, in short, will make the method callable without a class instance.
return teamList;
}
Since the TeamMember method show() is now static, you should be able to simply call TeamMember.show() and get the ArrayList.
Important note: In order for this to work, you must make the private arraylist static too. A static object cannot call a non-static object.
This will turn it into private static ArrayList<TeamMember> teamList = new ArrayList<>();
In the Main class, like I said above, simply call TeamMember.show(). You do not need to create an instance.

If you change your teamList to public instead of private your Main class will be able to access the variable. When you make something private in Java you're basically making that instance variable accessible only through the class that it's instantiated in. If you want the variable to be visible to other classes for reference you should make it public
Since the assignment calls for it, you're going to need to define a getter and setter for your 'teamList' variable.
public void setArray(ArrayList newTeamList){
teamList = newTeamList;
}
public ArrayList getArray(){
return teamList;
}
This'll allow you to access the private variable through the methods

object java class code

These are the instructions for this assignment. Any help would be appreciated. I am a rookie when it comes to java and cant seem to figure this out.
This exercise has two classes. The first class is named ObjectsToArrayList. The second class is called just Objects.
Your responsibility is to create the Object class and figure out how the ObjectsToArrayList class works.
The ObjectsToArraylist class will create an ArrayList of objects. It will ask for and populate the data fields of an Object, then add it to the ArrayList. This can be done for as many instances of the Object that the user wants to enter.
Requirements for the Object Class.
2 data fields: int obj_id, String obj_name.
2 Constructors: No-Arg and one that takes both values and assigns them to the data field.
Gets and sets for both data fields
A toString() method that returns output like:
The object ID is 22 and the name is Andrea
Here's my code
import java.util.*;
/**
*
* #author Student
*/
public class ObjectsToArrayList {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
ArrayList <Object> objectList = new ArrayList();
System.out.println("Please enter information for your favorite object!");
do { // collect an indicator to determine the method to call
Object object = new Object();
System.out.println("Enter a whole number for the ID of your object:\n"
+ "or enter 99 to quit.");
int tmpInt = input.nextInt();
// if 99 is entered exit the loop.
if (tmpInt == 99) {
break;
}
object.setObj_id(tmpInt);
input.nextLine();
// ask for the Object Name
System.out.println("Please enter the name of the Object:");
object.setObj_name(input.nextLine());
objectList.add(object);
} while (true); // this is a contineous loop if the break isn't included.
for(Object object:objectList) {
System.out.println(object.toString());
}
}
}
//****************************************************
//**** Objects Class is below this block **
//****************************************************
class Object {
// enter object code here (This is the part I cannot figure out)
}

Here are examples of constructors:
class Objects{
// This is a constructor with no argument
public Objects(){
}
// This is a constructor with 2 arguments
public Objects(int obj_id, String obj_name){
}
}
You can refer in the link below to learn more about creating constructors and assigning values to fields:
http://docs.oracle.com/javase/tutorial/java/javaOO/constructors.html
Note: Do not use Object as a class because Object is the root of the class hierarchy. Every class has Object as a superclass. All objects, including arrays, implement the methods of this class.
http://docs.oracle.com/javase/8/docs/api/java/lang/Object.html

Try something like this:
public class ObjectsToArrayList {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
ArrayList <Object> objectList = new ArrayList();
System.out.println("Please enter information for your favorite object!");
do { // collect an indicator to determine the method to call
Object object = new Object();
System.out.println("Enter a whole number for the ID of your object:\n"
+ "or enter 99 to quit.");
int tmpInt = input.nextInt();
// if 99 is entered exit the loop.
if (tmpInt == 99) {
break;
}
object.setObj_id(tmpInt);//runs the setObj_id method in the Objects class
//for the users input
input.nextLine();
// ask for the Object Name
System.out.println("Please enter the name of the Object:");
object.setObj_name(input.nextLine());//runs the setObj_name method in the Objects class
//for the users input
objectList.add(object);
} while (true); // this is a contineous loop if the break isn't included.
for(Object object:objectList) {
System.out.println(object.toString());//prints out what the toString method returns in
//the Objects class
}
}
}
//****************************************************
//**** Objects Class is below this block **
//****************************************************
public class Objects
{
//add stuff like methods and instance variables
private int ID;
private String name;
public Objects(){//default constructor
}
public Objects(int i, String n){//constructor to change both ID and name at the same time
ID = i;
name = n;
}
public void setObj_id(int i){//constructor to change only ID
ID = i;
}
public void setObj_name(String n){//constructor to change only name
name = n;
}
public String toString(){
return (name + ": " + ID);
}
}

Ok so you want to create your own object soo have 2 classes rather, personProfile and arrayOfProfiles
So class personDetails object note seperate class file not *not in same file
class personProfile{
private int ID = 0;
private String Name = "";
public personProfile(int id,String name){
ID = id;
Name = name;
}
public int getID(){
return ID;
}
public String getName(){
return name;
}
}
now the other class* different file
class arrayOfProfiles{
personProfile profiles[] = new personProfile[0];
public personProfile[] array(){
return profiles;
}
public void addProfileToArray(personProfile profileObject){
personProfile arrayMod = new personProfile[profiles.length+1];
for(int i = 0;i<profiles.length;i++){
arrayMod[i] = profiles[i];
}
arrayMod[arrayMod.length-1] = profileObject;
}
public static void main(String args[]){
arrayOfProfiles profiles = new arrayOfProfiles();
for(int i = 0;i<5;i++){
int id = Integer.parseInt(JOptionPane.showInputDialog("enter ID ");
String name = JOptionPane.showInputDialog("enter name");
profiles.addProfileToArray(new personProfile(id,name));
}
for(int i =0;i<profiles.array().length;i++){
System.out.println("ID :"+profiles[i].getID()+" name - "+profiles[i].getName());
}
}
}

How to write a 3 class program and have the main class trigger methods in the other two

I have to write a program with 3 classes and lots of different methods.
I've written a simpler example to try and get an idea where I am going wrong
First class (music) is defining a music object with three data types. And should have a method to print the contents of an array.
the second class (musicArray) has all the data for the array and should build the array when the third class tells it too.
the third class(searchclass) has the main method it should tell the second class to make the array then with user input search the array for songs that match the rating.
import java.util.Arrays;
public class Music extends musicArray {
private String songTitle;
private double songLength;
private int rating;
static String everything;
public Music(String songTitle, double songLength, int rating) {
this.songTitle = songTitle;
this.songLength = songLength;
this.rating = rating;
}
public String getsongTitle()
{
return songTitle;
}
public double getsongLength()
{
return songLength;
}
public int rating()
{
return rating();
}
#Override
public String toString() {
return "music{"+ "songTitle= " + songTitle + ", songLength= "
+ songLength + ",rating=" + rating + '}';
}
public Music[] printsonglibrary(char[][] songDetails){
for (int count = 0; count <= 6; count++)
{
return System.out.println(songDetails[count]);
System.out.println(" ");
}
}
}
public class musicArray extends Searchclass{
static Music song1 = new Music ("achy breaky", 5.32, 10);
static Music song2 = new Music ("billy",1.2, 8 );
static Music song3 = new Music ("hello", 1.5, 9 );
static //Create array and make posistion 0 = song1
Music[] songDetails ={song1,song2,song3};
import java.util.Scanner;
public class Searchclass {
public static void main(String[] args) {
for(int count = 1; count <= songDetails.length; count++){
system out put for debugging
System.out.println(songDetails.length);
System.out.println(songDetails[count - 1]);}
}
/* public String songSeach(){
System.out.println("what rating of song do you want to search for?");
Scanner keyboard = new Scanner(System.in);
int searchValue = keyboard.nextInt();
if searchValue == rating in array use the printsonglibrary
method in the music class to print the array entry
*/
}
}
If I have the main method in the musicArray class I can print the array
So the question is how do I make the Songdetails array available in the seachclass?

You shouldn't directly expose any variables of one class to another. Instead consider giving the MusicArray class (note that by convention class names should begin with a capital letter) a public method, say public void printOutSongDetails() that would print out the contents of the array. Your main method can then call this method off of the MusicArray object that it has created. e.g.,
Edit 1
Also, the Music class should most definitely not extend the MusicArray class for there is no way that a Music object should behave like a MusicArray object. And on the same token, MusicArray should not extend the SearchClass.
Edit 2
Note that there are several other significant issues with your code that each one would prevent it from compiling, and this suggests that you should modify how you program (if you can't use an IDE). Try to compile early and often, and only add new code to the program after fixing any compilation errors so that the current code base compiles.
Edit 3
A small code example of what I was describing above.
class SearchClass {
public static void main(String[] args) {
MusicArray musicArray = new MusicArray();
musicArray.addMusic(new Music("Foobars Unit", 10.4, 5));
musicArray.addMusic(new Music("Spamalot", 11.0, 7));
//... etc ...
musicArray.printOutSongDetails();
}
}
Also, you'll probably not want those static Music variables but rather give MusicArray a method to add Music to its array, a public void addMusic method that accepts a Music object as a parameter.

One way is to make it public public Music[] songDetails ={song1,song2,song3};
A better way is to provide getter:
public Music[] getSongDetails() {
return songDetails;
}