How to pass a parameter that is of type class into another class's constructor?

[john kaine]

im very new to programming and im super confused about something.
basically, i have 4 classes. 1 2 3 and 4. 4 can be called by 2 and 3. 1 can call on both 2 and 3 and 2 can also call on 1. i feel like thats really bad explaining but its the only way i can explain without posting all the code on(i dont even know how)
i made a 2 fields in class 1 of type 2 and of type 3.  the problem i have is when i try to call a method on the type 2 field that is from class 2, that method also then asks for a parameter of type 4 and i dont know what im supposed to input as this is all in the constructor.

i get the    method in class cannot be applied to given types     error message.

any help would be appreciated.

[Paul Clapham]

new persons wrote:i feel like thats really bad explaining

Yes, your instinct is correct. It is really bad explaining. But don't let that deter you, you can do better.

but its the only way i can explain without posting all the code on(i dont even know how)

Show us the code. Do you think there's too much code and we're going to be put off by having to scroll forever? That's quite possible. But your question is just about how to declare parameters, so we don't really need to see what's inside the methods and constructors. You could leave that out.

Or are you concerned about how to get the code from your machine to the forum? Copy it from your code editor and paste it in the box you're posting in. If necessary, copy it to somewhere else on your machine and delete irrelevant code before pasting what's left into the forum's post box. Don't worry too much about whether it looks good, anything is better than what we have so far and we're all friendly and used to beginners here.

And, welcome to the Ranch!

[john kaine]

the thing i was told to do was only to write code for this class im about to post, it is pretty empty atm i have to fill stuff out

import java.awt.Desktop;
import java.net.URI;
import java.net.URISyntaxException;

/**
 * This project implements a simple application. Properties from a fixed
 * file can be displayed. 
 * 
 * 
 */
public class PropertyViewer
{    
    private PropertyViewerGUI gui;     // the Graphical User Interface
    private Portfolio portfolio;
    
    /**
     * Create a PropertyViewer and display its GUI on screen.
     */
    public PropertyViewer()
    {
        gui = new PropertyViewerGUI(this);
        portfolio = new Portfolio("airbnb-london.csv");
        portfolio.getProperty(0);
        gui.showProperty();
        
    }

i just copied the naming of the fields and the constructor part.  what im struggling with is the last line. it asks for type Property but i have no clue what to write.  the other classes i added below.

/**
 * Property is a class that defines a property for display.
 * 
 */
public class Property
{

    private String id;
    private String description;
    private String hostID;
    private String hostName;
    private String neighbourhood;
    private double latitude;
    private double longitude;
    private String roomType;
    private int price;
    private int minimumNights;
    private int availability365;
    private boolean isFavourite;
    
    /**
     * Create a new property with specified initial values.
     */
    public Property(String id, String name, String hostID, String hostName, 
            String neighbourhood, double latitude, double longitude, String roomType, 
            int price, int minimumNights, int availability365){
		this.id = id;
        this.description = name;
        this.hostID = hostID;
        this.hostName = hostName;
        this.neighbourhood = neighbourhood;
        this.latitude = latitude;
        this.longitude  = longitude;
        this.roomType = roomType;
        this.price = price;
        this.minimumNights = minimumNights;
        this.availability365 = availability365;
        
        isFavourite = false;
    }
    
    /**
     * Return the Id of this property.
     */
    public String getID(){
        return id;
    }
    
    /**
     * Return the hostId of this property.
     */
    public String getHostID(){
        return hostID;
    }
    
    /**
     * Return the latitude of this property.
     */
    public double getLatitude(){
        return latitude;
    }
    
    /**
     * Return the longitude of this property.
     */
    public double getLongitude(){
        return longitude;
    }
    
    /**
     * Return the price of this property.
     */
    public int getPrice(){
        return price;
    }
    
    /**
     * Returns true if this property is currently marked as a favourite, false otherwise.
     */
    public boolean isFavourite(){
        return isFavourite;
    }
    
    /**
     * Return the host name of this property.
     */
    public String getHostName(){
        return hostName;
    }
    
    /**
     * Return the neighbourhood of this property.
     */
    public String getNeighbourhood(){
        return neighbourhood;
    }
    
    /**
     * Return the room type of this property.
     */
    public String getRoomType(){
        return roomType;
    }
    
    /**
     * Return the minimum number of nights this property can be booked for.
     */
    public String getMinNights(){
        return "" + minimumNights;
    }
    
    /**
     * Return the description of this property.
     */
    public String getDescription(){
        return description;
    }
    
    /**
     * Toggles whether this property is marked as a favourite or not.
     */
    public void toggleFavourite()
    {
        isFavourite = !isFavourite;
    }

}

that is the first class, the one i said was 4 if you managed to decrypt my message.

[john kaine]

import java.util.List;
import java.util.ArrayList;
import java.io.File;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import com.opencsv.CSVReader;
import java.net.URISyntaxException;

/**
 * A portfolio is a collection of properties. It reads properties from a file on disk,
 * and it can be used to retrieve single properties.
 * 
 * The file name to read from is passed in at construction.
 * 
 */
public class Portfolio
{
    private List<Property> properties; 

    /**
     * Constructor for objects of class Portfolio
     */
    public Portfolio(String directoryName)
    {
        properties = loadProperties();
    }

    /**
     * Return a property from this Portfolio.
     */
    public Property getProperty(int propertyNumber)
    {
        return properties.get(propertyNumber);
    }

    /**
     * Return the number of Properties in this Portfolio.
     */
    public int numberOfProperties()
    {
        return properties.size();
    }
    
     /**
     * Return an ArrayList containing the rows in the AirBnB London data set csv file.
     */
    public List<Property> loadProperties() {
        System.out.print("Begin loading Airbnb london dataset...");
        ArrayList<Property> listings = new ArrayList<Property>();
        try{
            URL url = getClass().getResource("airbnb-london.csv");
            CSVReader reader = new CSVReader(new FileReader(new File(url.toURI()).getAbsolutePath()));
            String [] line;
            //skip the first row (column headers)
            reader.readNext();
            while ((line = reader.readNext()) != null) {
                String id = line[0];
                String name = line[1];
                String host_id = line[2];
                String host_name = line[3];
                String neighbourhood = line[4];
                double latitude = convertDouble(line[5]);
                double longitude = convertDouble(line[6]);
                String room_type = line[7];
                int price = convertInt(line[8]);
                int minimumNights = convertInt(line[9]);
                int availability365 = convertInt(line[10]);

                Property currentProperty = new Property(id, name, host_id, host_name, 
                    neighbourhood, latitude,longitude, room_type, price,
                    minimumNights, availability365);
                listings.add(currentProperty);
            }
        } catch(IOException | URISyntaxException e){
            System.out.println("Failure! Something went wrong when loading the property file");
            e.printStackTrace();
        }
        System.out.println("Success! Number of loaded records: " + listings.size());
        return listings;
    }

    /**
     *
     * @param doubleString the string to be converted to Double type
     * @return the Double value of the string, or -1.0 if the string is 
     * either empty or just whitespace
     */
    private Double convertDouble(String doubleString){
        if(doubleString != null && !doubleString.trim().equals("")){
            return Double.parseDouble(doubleString);
        }
        return -1.0;
    }

    /**
     *
     * @param intString the string to be converted to Integer type
     * @return the Integer value of the string, or -1 if the string is 
     * either empty or just whitespace
     */
    private Integer convertInt(String intString){
        if(intString != null && !intString.trim().equals("")){
            return Integer.parseInt(intString);
        }
        return -1;
    }
}

this was 3.

[john kaine]

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;

import java.io.File;

import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;

/**
 * PropertyViewerGUI provides the GUI for the project. It displays the property
 * and strings, and it listens to button clicks.

 * @author Michael Kölling, David J Barnes, and Josh Murphy 
 * @version 3.0
 */
public class PropertyViewerGUI
{
    // fields:
    private JFrame frame;
    private JPanel propertyPanel;
    private JLabel idLabel;
    private JLabel favouriteLabel;
    
    private JTextField hostIDLabel;
    private JTextField hostNameLabel;
    private JTextField neighbourhoodLabel;
    private JTextField roomTypeLabel;
    private JTextField priceLabel;
    private JTextField minNightsLabel;
    private JTextArea descriptionLabel;
    
    private Property currentProperty;
    private PropertyViewer viewer;
    private boolean fixedSize;
        
    /**
     * Create a PropertyViewer and display its GUI on screen.
     */
    public PropertyViewerGUI(PropertyViewer viewer)
    {
        currentProperty = null;
        this.viewer = viewer;
        fixedSize = false;
        makeFrame();
        this.setPropertyViewSize(400, 250);
    }


    // ---- public view functions ----
    
    /**
     * Display a given property
     */
    public void showProperty(Property property)
    {
        hostIDLabel.setText(property.getHostID());
        hostNameLabel.setText(property.getHostName());
        neighbourhoodLabel.setText(property.getNeighbourhood());
        roomTypeLabel.setText(property.getRoomType());
        priceLabel.setText("£" + property.getPrice());
        minNightsLabel.setText(property.getMinNights());
        //descriptionLabel.setText(property.getDescription());
    }
    
    /**
     * Set a fixed size for the property display. If set, this size will be used for all properties.
     * If not set, the GUI will resize for each property.
     */
    public void setPropertyViewSize(int width, int height)
    {
        propertyPanel.setPreferredSize(new Dimension(width, height));
        frame.pack();
        fixedSize = true;
    }
    
    /**
     * Show a message in the status bar at the bottom of the screen.
     */
    public void showFavourite(Property property)
    {
        String favouriteText = " ";
        if (property.isFavourite()){
            favouriteText += "This is one of your favourite properties!";
        }
        favouriteLabel.setText(favouriteText);
    }
    
    /**
     * Show the ID in the top of the screen.
     */
    public void showID(Property property){
        idLabel.setText("Current Property ID:" + property.getID());
    }
    
    // ---- implementation of button functions ----
    
    /**
     * Called when the 'Next' button was clicked.
     */
    private void nextButton()
    {
        viewer.nextProperty();
    }

    /**
     * Called when the 'Previous' button was clicked.
     */
    private void previousButton()
    {
        viewer.previousProperty();
    }
    
    /**
     * Called when the 'View on Map' button was clicked.
     */
    private void viewOnMapsButton()
    {
        try{
         viewer.viewMap();
        }
        catch(Exception e){
            System.out.println("URL INVALID");
        }
        
    }
    
    /**
     * Called when the 'Toggle Favourite' button was clicked.
     */
    private void toggleFavouriteButton(){
        viewer.toggleFavourite();     
    }

    // ---- swing stuff to build the frame and all its components ----
    
    /**
     * Create the Swing frame and its content.
     */
    private void makeFrame()
    {
        frame = new JFrame("Portfolio Viewer Application");
        JPanel contentPane = (JPanel)frame.getContentPane();
        contentPane.setBorder(new EmptyBorder(6, 6, 6, 6));

        // Specify the layout manager with nice spacing
        contentPane.setLayout(new BorderLayout(6, 6));

        // Create the property pane in the center
        propertyPanel = new JPanel();
        propertyPanel.setLayout(new GridLayout(6,2));
        
        propertyPanel.add(new JLabel("HostID: "));
        hostIDLabel = new JTextField("default");
        hostIDLabel.setEditable(false);
        propertyPanel.add(hostIDLabel);
        
        propertyPanel.add(new JLabel("Host Name: "));
        hostNameLabel = new JTextField("default");
        hostNameLabel.setEditable(false);
        propertyPanel.add(hostNameLabel);
        
        propertyPanel.add(new JLabel("Neighbourhood: "));
        neighbourhoodLabel = new JTextField("default");
        neighbourhoodLabel.setEditable(false);
        propertyPanel.add(neighbourhoodLabel);
        
        propertyPanel.add(new JLabel("Room type: "));
        roomTypeLabel = new JTextField("default");
        roomTypeLabel.setEditable(false);
        propertyPanel.add(roomTypeLabel);
        
        propertyPanel.add(new JLabel("Price: "));
        priceLabel = new JTextField("default");
        priceLabel.setEditable(false);
        propertyPanel.add(priceLabel);
        
        propertyPanel.add(new JLabel("Minimum nights: "));
        minNightsLabel = new JTextField("default");
        minNightsLabel.setEditable(false);
        propertyPanel.add(minNightsLabel);

        propertyPanel.setBorder(new EtchedBorder());
        contentPane.add(propertyPanel, BorderLayout.CENTER);
        
        // Create two labels at top and bottom for the file name and status message
        idLabel = new JLabel("default");
        contentPane.add(idLabel, BorderLayout.NORTH);

        favouriteLabel = new JLabel(" ");
        contentPane.add(favouriteLabel, BorderLayout.SOUTH);
        
        // Create the toolbar with the buttons
        JPanel toolbar = new JPanel();
        toolbar.setLayout(new GridLayout(0, 1));
        
        JButton nextButton = new JButton("Next");
        nextButton.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { nextButton(); }
                           });
        toolbar.add(nextButton);
        
        JButton previousButton = new JButton("Previous");
        previousButton.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { previousButton(); }
                           });
        toolbar.add(previousButton);

        JButton mapButton = new JButton("View Property on Map");
        mapButton.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { viewOnMapsButton(); }
                           });
        toolbar.add(mapButton);
        
        JButton favouriteButton = new JButton("Toggle Favourite");
        favouriteButton.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { toggleFavouriteButton(); }
                           });
        toolbar.add(favouriteButton);


        // Add toolbar into panel with flow layout for spacing
        JPanel flow = new JPanel();
        flow.add(toolbar);
        
        contentPane.add(flow, BorderLayout.WEST);
        
        // building is done - arrange the components     
        frame.pack();
        
        // place the frame at the center of the screen and show
        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setLocation(d.width/2 - frame.getWidth()/2, d.height/2 - frame.getHeight()/2);
        frame.setVisible(true);
    }    
}

this was 2.

[Paul Clapham]

john kaine wrote:i get the    method in class cannot be applied to given types     error message.

Okay. Then it would be useful for us to know exactly which line of code produced that message.

Maybe you get it more than once? Then you could tell us about every line of code which produces it.

[john kaine]

i was struggling with the last line on the 1st message that said gui.showProperty().  i spent about 3 hours on that one line before realising that i had to enter the line before it (the portfolio.getProperty(0) line) as the paramter for the gui.showProperty().  as painful as it was to waste so much time on something so easy you were probably cringing actually gave me suuuuch a huge smile.

[Campbell Ritchie]

Welcome to the Ranch

Please look at our link about the code button; it isn't obvious at first how to use it, but you put the code between the [‍code=java] part and the [‍/code] part. Since you are new I have corrected it.
If you hit problems, please ask for help early; it is much easier to help if you have written only a little code. The small parts I have read look good, but why are you matching a field description with a constructor parameter name?

Actually passing parameters to constructors is the same whether they are reference types or primitives. Let's have a Kettle which contains water when new, so its constructor might look like this:-

public Kettle(int capacity, String make, Water w)
{
   // ...
}

. . . and you can call it like this, assuming the Water object already exists:-

Kettle k = new Kettle(20, "Swan", myWater);

Beware: Strings are immutable and ints are primitives, so there is no need for a defensive copy of them, but Water might be mutable, so take a defensive copy OR tease the object apart into primitives and immutable objects, to maintain the integrity of your object. Your property class doesn't (I think) need any defensive copying.
Two old posts about defensive copies: 1 2.

[Paul Clapham]

john kaine wrote:i was struggling with the last line on the 1st message that said gui.showProperty().  i spent about 3 hours on that one line before realising that i had to enter the line before it (the portfolio.getProperty(0) line) as the paramter for the gui.showProperty().  as painful as it was to waste so much time on something so easy you were probably cringing actually gave me suuuuch a huge smile.

Yeah, we've all been there. I remember... but everyone has their own anecdotes. So, for you it's on to the next tar pit!

[Campbell Ritchie]

Paul Clapham wrote:. . . Yeah, we've all been there. I remember... . . .

I once spent two hours wondering why my method called throw() wouldn't compile.

on to the next tar pit!

You're such an incurable optimist, aren't you, Paul

[john kaine]

well it looks like i have a lot to learn :p