Accessing object variable in extended generic arraylist

user_13045538 0
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For an assignment, I have to create and manipulate a generic object arraylist MyArrayList<E> extended from java.util.ArrayList<E>. I need to access a variable highScore inside the object GameEntry for the purpose of adding the entry into a MyArrayList if it meets the requirements, but I can't seem to do it?

GameEntry class

public class GameEntry
{   public String name;
    public int highScore;
    public String handle;

    public GameEntry()
    {   name = this.name;
        highScore = this.highScore;
        handle = this.handle;
    }

    public GameEntry(String n, int hs, String h)
    {   name = n;
        highScore = hs;
        handle = h;
    }

    public String getName() { return name; }
    public int getHScore() { return highScore; }
    public String getHandle() { return handle; }

    public String toString() {
        return "(" + handle + ", " + name + ": " + highScore + ")";
    }
}

MyArrayList class

public class MyArrayList<E> extends java.util.ArrayList<E>
{   private int numEntries = 0;
    public MyArrayList() { super(); }
    public MyArrayList(int capacity) { super(capacity); }

    public boolean isListEmpty() { return this.isEmpty(); }

    // add new score to MyArrayList (if it is high enough)
    public void addInOrder(GameEntry e) {
        int newScore = e.getHScore();

        // is the new entry e really a high score?
        if(numEntries<this.size() || newScore > this.get(numEntries-1).getHScore())
        //ERROR: cannot find symbol - method getHScore()
        // ...rest of addInOrder code...
        }
    }    
}
arraylist generics java
1 Answers

You are getting this error because this.get(numEntries - 1) will return a generic, and the program will not be able to use getHScore() with it unless you cast it to GameEntry.

You can do this by checking to see if it is a GameEntry object with instanceof and then casting it:

public void addInOrder(GameEntry e) {
    int newScore = e.getHScore();

    // is the new entry e really a high score?
    if (this.get(numEntries - 1) instanceof GameEntry) {

        GameEntry ge = (GameEntry) this.get(numEntries - 1); //Cast to GameEntry
        if(numEntries<this.size() || newScore > ge.getHScore()) {
            //Do whatever
        }
    }
   //Add behavior for when it is NOT an instance of GameEntry
}

There are probably better ways to implement the behavior you want for addInOrder, but I thought I'd answer your literal question on why getHScore() is not working for you correctly.

user_114345520
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