Probably really simple solution!

Hey guys, basically i have been asked to create a program that helps a shop manage its art gallery. i am stuck on the method that allows me to print my ArrayList<Art> collection; in order of value. i can print out all elements of collection no problem but i cannot sort for some reason.

i have tried using implements Comparable<collection> but i get the error cannot find class, and saying it is not an abstract class so it cannot overide compareTo method. but i dont have a compare to method :)

Code:

---


import java.util.*;
import java.io.*;


public class Inventory
{
    private Art a; //holds the Art class and allows piece collection
    private String name;
    private Scanner scan; //allows user input
    private int total; //total value of the collection
    private List<Art> collection;
    private int nextFreeLocation; //used to determine size
    private int capacity;
    private double sessionTotal; //allows me to keep a running total for session
    public double VAT=0.2; //public variable for VAT

    public Inventory(int maxCollectionSize)
    {
        nextFreeLocation=0; //empty array so next free location is 0
        capacity=maxCollectionSize;
        scan=new Scanner(System.in);
        collection=new ArrayList<Art>(capacity);

    }

    /**
    * This method sets the name attribute
    * this method allows us to name the inventory
    * example "ChrisShop"
    *
    * @param inventoryName
    */

    public void setName(String inventoryName)
    {
        inventoryName=name;
    }

    /**
    * This method allows us to return the name of the inventory
    *
    * example return "ChrisShop"
    *
    * @return String
    */
    public String getName()
    {
        return name;
    }

    /**
    * This methods allows us to "count" the elements in the inventory
    * it does this by returning the next free 'space'
    *
    * @return int
    */
    public int getNumOfPieces()
    {
        return nextFreeLocation;
    }

    /**
    * This method allows the user to create a piece to add to inventory
    * this is ran externally through the Menu class
    * it is called when the user inputs the correct input:
    * this case being '1'
    * @param Art a
    *
    */
    public void addArt(Art a)
    {
        a=new Art();
        System.out.println("enter name of artist \n");
        String artist=scan.nextLine();
        System.out.print("enter name of art piece \n");
        String name=scan.nextLine();
        System.out.print("Enter value of art piece \n");
        int value=scan.nextInt();
        System.out.print("Enter file name of art piece \n");
        String image=scan.nextLine();
        //finished constructing dog(x, x, x);
        a=new Art(artist, name, value, image);
        collection.add(a);

    }

    /**
    * prints information about the pieces in Inventory
    *
    * @return String
    */
    public String toString() {

        /*code adapted from worksheet 5-daphne, by Lynda
        * added my own class names and toString
        */
        String results = "Pieces in Shops Invetory are:";
        for (Art a:collection)
        {
            results = results + a.toString() + "\n";
        }
        return results;
    }

    /**
    *  save() method writes data back to file
    *  this will write all the to strings for each piece in collection
    *  to the specified text file called from UserMenu in Menu class
    *  try catch block prevents bombing, as expecption is caught and handled
    *  @param fileName file to write to called in UserMenu
    */
    public void save(String fileName)
    {

        /*
        * adapted from Lynda's Contact code, made it handle my arrays
        * and my art toString
        */
        System.out.println("**method save writes data back to a file "+fileName);
        try {
            PrintWriter outfile = new PrintWriter(new OutputStreamWriter
                    (new FileOutputStream(fileName)));
            outfile.println(collection.size());
            for (Art a:collection) {
                /*
                * reason i have adapted this code as follows:
                * if i chose to to a.tostring it would cause my load method to bomb
                * This way saving each variable to a new line allows
                * my load method to read the same file allowing me to save/load
                *                  *
                */
                outfile.println(a.getArtist()); //stores only this variable
                outfile.println(a.getTitle());
                outfile.println(a.getValue());
                outfile.println(a.getFileName());
                //can also use any other art method such as getValue
            }
            outfile.close();
        }
        catch (IOException e) {

            System.out.println("file not found try again");

            //trycatch prevents bombing
        }
    }

    /**
    * load() method reads from a file
    * @param fileName file to read from
    * the file must be of the form
    * hense why save method prints variables instead of a.toString
    * 5(X) (num) must match the amount of art pieces in the file
    *artist
    *title
    *value
    *filename - must include file extension e.g xxx.jpeg
    *called from UserMenu in Menu class
    * try catch block prevents bombing, as expecption is caught and handled
    */
    public void load(String fileName){

        /*
        * Code adapted from Lynda's worksheet 5 - Daphne
        * adapted to understand my code and arrays
        */

        try // prevents crashing if no exsistent file is inputted
        {

            {
                System.out.println("reads using file "+fileName);

                Scanner infile =new Scanner(new InputStreamReader
                        (new FileInputStream(fileName)));
                int num=infile.nextInt();          // counts lines in file ready for loop:
                for (int i=0;i<num;i++) {      //loops through everyline in the file
                    String artist=infile.next(); //check for next string in the file and it becomes name
                    String name=infile.next(); //check for next string in file it becomes owner
                    int value=infile.nextInt();//checks for next int it becomes value
                    String image=infile.next();
                    Art a=new Art(artist, name, value, image);  //created new art piece using these variables from file
                    collection.add(a); //adds the new piece(a) based off file read and loaded
                }
                infile.close();
            }
        }
        catch (IOException e)
        {
            System.out.println("File not found - please try again");
        }

    }

    public void print() {
        System.out.println("The pieces in the Inventory are: \n");
        for(Art a: collection){
            System.out.println(a.toString()); //executes Art toString
            Collection.sort(collection);
        }
    }

    public void totalValue()
    {
        /*
        *Below method taken from useful collections worksheet
        *i have ammended the code to allow for use within my project
        * added total as my own variable
        * allowed it to serach my collections list
        *
        */
        Scanner avg=new Scanner(System.in);//for use in  calling avg method
        String q;//for use in calling avg method
        int subTotal=0;
        for(Art a:collection){
            subTotal += a.getValue();
        }
        total=subTotal; //gives total a value for sue with other methods
        System.out.println("Total value of collection is: £"+total);
        System.out.println("Would like to find the average value of collection? (yes or no)");;
        q=scan.nextLine();
        if(q.equals("yes")){
            averageValue();
        }else {
            return; //jumps out of method
        }
    }

    private void averageValue()
    {
        /*
        * set method to private so it cant be called before total value is calculated
        * will be called after totalValue has been called so it has data to
        * calculate and prevent errors.
        */
        double averageValue=total/collection.size();
        System.out.println("The average Value of the collection is £"+averageValue);
        return;

    }

    /**
    * Enables a user to delete Search the collection for an Ar piece.
    * Searches the ArrayList<Art> collection: for "title"
    * if it find this it will display the toString(a),
    * return jumps it out the method so after it finds the piece so method is stopped
    * @param title
    */
    public void searchForPiece(String title) {
        /*
        * The below code has been adapted from my own worksheet 5/6 in CS122.
        * the way in which i created this method was to use information provided by Lynda on searching arrays
        * then created an equals and something to return accordingly
        *          *
        *search for Art and print toString
        */
        for (Art a:collection) {
            if (title.equals(a.getTitle()))  {
                System.out.println(a.toString());

                return; //jump out of method
            }
        }
        System.out.println("Piece not in collection, please try again");
    }

    /**
    * Enables a user to delete Search the collection for an Art
    * piece also prints recipt and removes piece if sold
    * Searches the ArrayList<Art> collection: for "title"
    * if it find this it will display the toString(a),
    * return jumps it out the method so after it finds the piece so method is stopped
    * @param title
    */
    public void SellPieceAndRecipt(String title) {
        /*
        * The below code has been adapted from my own worksheet 5/6 in CS122.
        * the way in which i created this method was to use information provided by Lynda on searching arrays
        * then created an equals and something to return accordingly
        *          *
        *search for Art and remove from array list whilst printing a "recipt"
        */
        for (Art a:collection) {
            if (title.equals(a.getTitle()))  {  //title = search param "String title"
                /*
                * creating the recipt, adding variables as needed some methods acces each other
                * also since selling an Art piece removes it from array i used a scanner
                * to confirm sale (removal) to avoid accidental deleted
                * recipt will be printed before this is asked
                * recipt all created by me using standard println and
                * creating suitable variables and simple math for calcs.
                * also if the piece is sold it will display a running total for this 'session'
                *
                */

                //start of recipt and variables
                double c; //for use with payment
                System.out.println("********** TRANSACTION RECIPT *******");
                System.out.println(" The transaction is as follows ");
                System.out.println(" Piece name  " +title);
                int price=a.getValue();
                System.out.println(" Price  £" +price);
                double vatTotal=price*VAT;
                System.out.println(" VAT @ 20%  £"+vatTotal);
                double rest=price-vatTotal; //calculating price after vat been deducted
                System.out.println(" Sale price -VAT  £"+rest);
                double artistOwed=rest*0.75; //creating artist owed variable 75%
                System.out.println(" Artist owed (75% of fee)  £"+artistOwed);
                double gallery=rest*0.25; //25% percentage calc
                System.out.println(" Gallery recieves  £" +gallery);
                System.out.println(" Total for sale  £"+price);

                //end of recipt print

                //confirm sale using scanner, thus removing piece
                String q;//input variable for scanner
                System.out.println("Would to complete sale? (yes or no)");
                q=scan.nextLine(); //user responce
                if(q.equals("yes")){
                    sessionTotal += price; // keeps a running total of the sales
                    collection.remove(a);
                    System.out.println("Item sold, thank you for your custom!" );
                    System.out.println("Total for this session £"+sessionTotal); //displays total for this session based on sales
                    return; //jumps out of method
                }else {
                    System.out.println(" Transaction incomplete, item not removed");
                    System.out.println(" ******** END ******");
                    return; //jumps out of method
                }

            }
        }
        System.out.println("Piece not in collection, please try again");
    }

}

---

That class has the array list i need to sort in

This class (Art) are the elements of the array list

Code:

---



public class Art
{
    private String artist;
    private String title;
    private int value;
    private String filename;

    public Art()

    {

        artist="unknown";
        title="unknown";
        value=0;

    }

    public Art(String artistName, String pieceTitle, int worth, String image)
    {
        artist=artistName;
        title=pieceTitle;
        value=worth;
        filename=image;

    }

    public void setArtist(String artistName)
    {
        artistName=artist;

    }

    public String getArtist()
    {
        return artist;
    }

    public void setTitle (String pieceName)
    {
        pieceName=title;

    }

    public String getTitle()
    {
        return title;

    }

    public void setValue(int worth)
    {
        worth=value;
    }

    public int getValue()
    {
        return value;
    }

    public void setFileName(String image)
    {
        image=filename;

    }

    public String getFileName()
    {
        return filename;
    }

    public String toString(){
        if (value==0) {
            return " This piece is by " +artist+ " and is called " +title+ " and has no value" ;
        }
        else {
            return " This piece is by " +artist+ " and is called " +title+ " and is worth £"+value;
        }
    }

}

---

any ideas?

Thanks.

Perhaps this would be useful to you?

How to sort an ArrayList in java

i tried many websites like that, but the point im trying to make is i cant use Collection.sort(collection);
i get the error message:
no suitable method found for sort(java,util.List<Art>
method java.util.Collections<T>sort(java.util.List<T>,jav a.util.Comparator<? super T> is not applicable;
(cannot instantiate from arguments because actual and formal arguments differ in length);

Quote:

---

Originally Posted by monkeyjr97

i tried many websites like that, but the point im trying to make is i cant use Collection.sort(collection);
i get the error message:
no suitable method found for sort(java,util.List<Art>
method java.util.Collections<T>sort(java.util.List<T>,jav a.util.Comparator<? super T> is not applicable;
(cannot instantiate from arguments because actual and formal arguments differ in length);

---

Make your Art class implement the Comparable<Art> interface; you must implement one single method in that class: public int compareTo(Art a) { ... } Read the API documentation for the Comparable<T> interface for details.

kind regards,

Jos

monkeyjr97, please go through the Forum Rules -- particularly the third paragraph.

db

sorry DarrylBurke!

got it all working now cheers guys!