CODEWITHSUNDEEP
javaclassobjectarraylist
user3221439
user3221439

Reputation: 3

How can I access a part of an object that is part of an ArrayList?

as the title says. I have two classes, one that makes a "player", and another that makes a "team", which includes an arraylist of players. one of my methods in the team class is howmanyallstars, where I try to see how many allstars there are on the team, but I'm getting an error on my boolean. 

public class Player {
private String nameofplayer;
private int currentposition;
private double baverage;
private boolean allstar;

public Player (String name, int position, double battingaverage, boolean isallstar) {

    nameofplayer = name;
    currentposition = position;
    baverage = battingaverage;
    allstar = isallstar;

}

then I have:

public class Team {

private String nameteam;
private static ArrayList roster;
private double priceofgame;
private double budget;
private int numberofgames;

public Team (String teamname, ArrayList teamroster, double price, double teambudget, int games) {

    nameteam = teamname;
    roster = teamroster;
    priceofgame = price;
    budget = teambudget;
    numberofgames = games;
}


public static int numberOfAllstars(Team name) {

    int rostersize = roster.size();

    int numofallstars = 0;
    for (int counter = 0; counter <= rostersize; counter++) {

        if (roster.get(counter).allstar == true)  numofallstars++;
    }

    return numofallstars;
}

as I said, the .allstar is being flagged, and I don't know how to fix it. Can someone please help?

Upvotes: 0

Views: 131

Answers (5)

mburke13
mburke13

Reputation: 500

One problem is you declared roster as a generic ArrayList without any type information.

roster.get(counter) will return an Object instead of a Player.

You can solve this two ways:

  1. Declare roster as an ArrayList of Player objects instead of as a generic ArrayList

    private static ArrayList<Player> roster;

  2. Cast roster.get(counter) to an object of type Player

    if (((Player) roster.get(counter)).allstar == true) {
    numofallstars++;
}

Another problem is that you have declared allstar as a private variable in the Player class. Private variables can only be accessed by the class in which they are declared.

The best solution to this is not to change the visibility of the variable from private to public. Instead, you should create an accessor method to retrieve the value of the variable from outside of the class.

Here is an example:

private boolean allstar;

//...

public boolean isAllstar() {
    return allstar;    
}

A third problem is see is that your method, numberOfAllstars, will throw an exception because the for loop's terminating condition is incorrect.

Just like Arrays, Lists of size n will be accessed with indices starting at 0 and ending at n - 1. Because your for loop terminates when counter <= rosterSize, your next line will try to access the List at an index equal to its size. This index is invalid for the List, so an exception will be thrown.

Here is the correct way to write the loop:

for (int counter = 0; counter < rosterSize; counter++)

Upvotes: 1

Ali Alavi
Ali Alavi

Reputation: 2467

1- Define allstar in your class as public, or use a public get/private set property:

private bool _allstar = false;

public string allstar
{
    get
    {
        return name;
    }
    private set
    {
        name = _allstar;
    }
}

2- It is better to define roster list as an ArrayList<Player>.

3- You can use linq to make your function a one liner:

public static int numberOfAllstars(Team name) {
    return roster.Where (e=>e.allstar).Count();
     }

Upvotes: 0

rgettman
rgettman

Reputation: 178263

First, your roster is of the raw form of ArrayList, so the get method will return an Object, not a Player. Use generics to specify "of what" on your ArrayList:

private static ArrayList<Player> roster;

and in your Team constructor:

public Team (String teamname, ArrayList<Player> teamroster, double price,
    double teambudget, int games) {

Next, allstar is a private field in Player. Create a public getter method and call it instead of referencing the field directly.

Next, for some reason your roster variable and numberOfAllstars method are static. There's no reason for that. Just make everything non-static here. Also, there's no reason for the name parameter on numberOfAllStars; it can be removed.

Additionally, once you do that, you will run off the end of the array with this for loop, because indexes range from 0 to size() - 1.

for (int counter = 0; counter <= rostersize; counter++) {

Try

for (int counter = 0; counter < rostersize; counter++) {

And, the comparison to true is unnecessary; the condition is already a boolean. Try

if (roster.get(counter).isAllstar())

(once you've made the getter method isAllstar().

Upvotes: 2

Alexis C.
Alexis C.

Reputation: 93842

The problem is that the allStar field is private. So you can't access it in your Team class. You need to create a getter to access the allstar value for your player class.

public class Player {



     public boolean isAllStar(){
          return this.allStar;
     }
}

Then you'll be able to call it in your loop :

public static int numberOfAllstars(Team name) {

    int numofallstars = 0;    
    for (int counter = 0; counter < roster.size(); counter++) {
        if (roster.get(counter).isAllStar())  numofallstars++;
    }

    return numofallstars;
}

Note that arrays are 0 base indexed so if should be counter < roster.size(). Also don't use raw types, use generics.

ArrayList<Player> roster;

Upvotes: 1

MGorgon
MGorgon

Reputation: 2607

private boolean allstar; is private, so you can't access it outside of Player class. Make geter for it in Player class:

public boolean getAllstar() {
    return allstar;
}

and then, in Team class:

if (roster.get(counter).getAllstar())  numofallstars++;

Upvotes: 1

Related Questions