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How can i use two extended classes in java

I am learning about java inheritance and i am a bit confused, if i write a program that handles 3 files:
1) cheese.txt
2) fruits.txt
3) drinks.txt
If i have a parent class called Food that handles fruits.txt
and a class Cheese that handles cheese.txt that extends Foods
and a class Drinks that handles drinks.txt that extends Foods
so it looks like this
class Foods {
// code
}
class Cheese extends Foods {
// code
}
class Drinks extends Foods {
// code
}
public static void main(String[] args) {
Foods one = new Foods("fruits.txt"); // call to constructors
Cheese two = new Cheese("cheeses.txt"); // call to constructors
Drinks three = new Drinks("drinks.txt"); // call to constructors
}
How ever upon running this code it seems like the last class (Drinks) overlaps all the other classes. If i comment out the object three it works properly. How can i use all 3 classes in the main method at one time?

First of all, like others suggested you to do, you should show us the class with all the code in it so it would be easier for us to help you.
Second of all, you need to check all those things :
(good source of "documentation" is https://www.w3schools.com/java/java_files_read.asp)
1- Check if you have all your imports right :
import java.io.File; // Import the File class
import java.util.Scanner; // Import the Scanner class to read text files
2- Check if you code is something similar to that :
File myObj = new File("filename.txt"); // allows you to "bind" the file and use it for manipulations
Scanner myReader = new Scanner(myObj); // allows you to do manipulations on your determined file
while (myReader.hasNextLine()) { // make sure that as long as there is another line that the reader has not read, it continues to read the file
String data = myReader.nextLine(); // where the read line is stored
System.out.println(data); // print the determined line
If you could show us both the super-class and the inheriting classes, it would

Creating a Input Char menu

Coding a Ask for Char menu
Trying to construct a menu in which allows a user to add or view parts from a linkedlist. Ive been following a tutors video, however when he enters In.nextChar his program works fine, however my program wont accept that as an option/method of obtaining the users input.
The code is exactly the same as the tutors but as you can see I get the error where return In.nextChar(); is

I suggest using something like an ArrayList as storage for your Parts.
public class Catalogue {
private ArrayList<Part> parts;
public Catalogue() {
parts = new ArrayList<Part>();
}
}
if you want to be able to add certain Parts to the Catalogue you can just add the the Part-Instances to the ArrayList by
Part myExamplePart = new Part(...);
parts.add(myExamplePart);

Comparing strings from a written file

I'm stuck on this program I'm making for school. Here's my code:
public static void experiencePointFileWriter() throws IOException{
File writeFileResults = new File("User Highscore.txt");
BufferedWriter bw;
bw = new BufferedWriter(new FileWriter(writeFileResults, true));
bw.append(userName + ": " + experiencePoints);
bw.newLine();
bw.flush();
bw.close();
FileReader fileReader = new FileReader(writeFileResults);
char[] a = new char[50];
fileReader.read(a); // reads the content to the array
for (char c : a)
System.out.print(c); // prints the characters one by one
fileReader.close();
}
The dilemma I'm facing is how can I sort new scores with the scores in writeFileResults by the numerical value of int experiencePoints? If you're wondering about the variables userName is assigned by a textfield.getText method, and an event happens when you press one of 36 buttons which launches a math.Random statement with one of 24 possible outcomes. They all add different integer numbers to experiencePoints.

Well, I don't want to do your homework, and this does seem introductory so I'd like to give you some hints.
First, there's a few things missing:
We don't have some of the variables you've given us, so there is no type associated with oldScores
There is no reference to userName or experiencePoints outside this method call
If you can add this information, it would make this process easier. I could infer things, but then I might be wrong, or worse yet, have you learn nothing because I did your assignment for you. ;)
EDIT:
So, based on extra information, you're data file is holding an "array" of usernames and experience values. Thus, the best way (read: best design, not shortest) would be to load these into custom objects then write a comparator function (read: implement the abstract class Comparator).
Thus, in pseudo-Java, you'd have:
Declare your data type:
private static class UserScore {
private final String name;
private final double experience;
// ... fill in the rest, it's just a data struct
}
In your reader, when you read the values, split each line to get the values, and create a new List<UserScore> object which contains all of the values read from the file (I'll let you figure this part out)
After you have your list, you can use Collections#sort to sort the list to be the correct order, here would be an example of this:
// assuming we have our list, userList
Collections.sort(userList, new Comparator<UserScore>() {
public int compare(UserScore left, UserScore right) {
return (int)(left.getExperience() - right.getExperience()); // check the docs to see why this makes sense for the compare function
}
}
// userList is now sorted based on the experience points
Re-write your file, as you see fit. You now have a sorted list.

CSV to a String Array - JAVA

I have a CSV file which has only one column with 100+ rows. I would like to put those values in an one dimensional array(only if its possible). So that it works as same as if I wrote a string array manually. I.e.
String[] username = {'lalala', 'tatata', 'mamama'}; //<---if I did it manually
String[] username = {after passing the CSV values}; //<---I want this like the above ones.
Then later I would like to be able to initialized that class to a different class, say if the class that holds the array is called ArrayClass, I would like to be able to initialized this to different class, like this --
public class MainClass{
ArrayClass array = new ArrayClass();
//Then I would like to be able to do this
someMethod(array.username);
}
I know I asked a lot of things but I seriously appreciate all your help. Even if you see this question and say THIS IS BS. Oh and one more thing I would prefer it to be in JAVA.

It might be easier to use an arraylist rather than an array as you dont have to worry about number of rows. An array has a fixed size that cant be changed. i.e ArrayList
As you have only one column you will not need to worry about commas in csv
Example code would look something like this:
import java.util.*;
import java.io.*;
public class MyClass {
private ArrayList<String> MyArray = new ArrayList<String>();
private Scanner scan;
public MyClass(){
try {
scan = new Scanner(new File("MyFile.csv"));
} catch (IOException ioex) {
System.out.println("File Not Found");
}
}
public ArrayList<String> getArray() {
while (scan.hasNext()) {
Scanner line = new Scanner(scan.nextLine());
MyArray.add(line.next());
}
return MyArray;
}
}
And in the main:
MyClass f = new MyClass();
System.out.println(f.getArray());

If it's just a csv you can use the split method of string with a proper regex.
Please do check the split method

The first half of your question is easy and can be handled in a number of different ways. Personally, I would use the Scanner class and set the delimiter to be ",". Create a new Scanner Object and then call setDelimiter(",") on it. Then simply scan through the tokens. See the example on the documentation. This method of doing things is effective because it handles reading in the file and separating it based on your criteria (the ',' character).

problems with RequestForFile() class that is using User class in Java

Okay I'll try to be direct.
I am working on a file sharing application that is based on a common Client/Serer architecture. I also have HandleClient class but that is not particularly important here.
What I wanna do is to allow users to search for a particular file that can be stored in shared folders of other users. For example, 3 users are connected with server and they all have their respective shared folders. One of them wants to do a search for a file named "Madonna" and the application should list all files containing that name and next to that file name there should be an information about user(s) that have/has a wanted file. That information can be either username or IPAddress. Here is the User class, the way it needs to be written (that's how my superiors wanted it):
import java.io.File;
import java.util.ArrayList;
import java.util.Scanner;
public class User {
public static String username;
public static String ipAddress;
public User(String username, String ipAddress) {
username = username.toLowerCase();
System.out.println(username + " " + ipAddress);
}
public static void fileList() {
Scanner userTyping = new Scanner(System.in);
String fileLocation = userTyping.nextLine();
File folder = new File(fileLocation);
File[] files = folder.listFiles();
ArrayList<String> list = new ArrayList<String>();
for (int i = 0; i < files.length; i++) {
list.add(i, files[i].toString().substring(fileLocation.length()));
System.out.println(list.get(i));
}
}
public static void main(String args[]) {
System.out.println("Insert the URL of your shared folder");
User.fileList();
}
}
This class stores attributes of a particular user (username, IPAddress) and also creates the list of files from the shared folder of that particular user. the list type is ArrayList, that's how it has to be, again, my superiors told me to.
On the other hand I need another class that is called RequestForFile(String fileName) whose purpose is to look for a certain file within ArrayLists of files from all users that are logged in at the moment of search.
This is how it should look, and this is where I especially need your help cause I get an error and I can't complete the class.
import java.util.ArrayList;
public class RequestForFile {
public RequestForFile(String fileName) {
User user = new User("Slavisha", "84.82.0.1");
ArrayList<User> listOfUsers = new ArrayList();
listOfUsers.add(user);
for (User someUser : listOfUsers) {
for (String request : User.fileList()) {
if (request.equals(fileName))
System.out.println(someUser + "has that file");
}
}
}
}
The idea is for user to look among the lists of other users and return the user(s) with a location of a wanted file.
GUI aside for now, I will get to it when I fix this problem.
Any help appreciated.
Thanks
I'm here to answer anything regarding this matter.

There are lots of problems here such as:
I don't think that this code can compile:
for (String request : User.fileList())
Because fileList() does not return anything. Then there's the question of why fileList() is static. That means that all User objects are sharing the same list. I guess that you have this becuase you are trying to test your user object from main().
I think instead you should have coded:
myUser = new User(...);
myUser.fileList()
and so fileList could not be static.
You have now explained your overall problem more clearly, but that reveals some deeper problems.
Let's start at the very top. Your request object: I think it represents one request for one user with one file definition. But it needs to go looking in the folders of many users. You add the the requesting user to a list, but what about the others. I think that this means that you need another class responsible for holding all the users.
Anyway lets have a class called UserManager.
UserMananger{
ArrayList<User> allTheUsers;
public UserManager() {
}
// methods here for adding and removing users from the list
// plus a method for doing the search
public ArrayList<FileDefinitions> findFile(request) [
// build the result
}
}

in the "line 14: for (String request : User.fileList()) {" I get this error: "void type not allowed here" and also "foreach not applicable to expression type"
You need to let User.fileList() return a List<String> and not void.
Thus, replace
public static void fileList() {
// ...
}
by
public static List<String> fileList() {
// ...
return list;
}
To learn more about basic Java programming, I can strongly recommend the Sun tutorials available in Trials Covering the Basics chapter here.

It looks like you're getting that error because the fileList() method needs to returns something that can be iterated through - which does not include void, which is what that method returns. As written, fileList is returning information to the console, which is great for your own debugging purposes, but it means that other methods can't get any of the information fileList sends to the console.
On a broader note, why is RequestForFile a separate class? If it just contains one method, you can just write it as a static method, or as a method in the class that's going to call it. Also, how will it get lists of other users? It looks like there's no way to do so as is, as you've hard-coded one user.
And looking at the answers, I'd strongly second djna's suggestion of having some class that acts as the controller/observer of all the Users.