How to add this to an ArrayList

[lo2]

Hey there I trying to make a kind of spreadsheet in java, we are implementing it step by step of course. But we have something called a node which contains a position and an expression, each node should represent a cell in our spreadsheet.

We then would like to add these to the ArrayList, and for this I have written the following:

package spreadsheet;
import java.util.ArrayList;

public class Spreadsheet {
private ArrayList<Node> sheet;

  public Spreadsheet() {
    sheet = new ArrayList<Node>();
  }

  public void set(final Position position, final Expression expression) { 
    sheet.add(position, expression);
  }

But I get this error code then:

error: no suitable method found for add(Position,Expression)
sheet.add(position, expression);
^
method ArrayList.add(int,Node) is not applicable
(actual argument Position cannot be converted to int by method invocation
conversion)
method ArrayList.add(Node) is not applicable
(actual and formal argument lists differ in length)

So well I guess I am adding these elements in the wrong way, so I how should I do it diffrently?

[Sierra]

You need to add a object of the type you created the list with: "Node"
try e.g.: add(new Node(position, expression) )

[lo2]

You need to add a object of the type you created the list with: "Node"
try e.g.: add(new Node(position, expression) )

Ah yeah ok, it is because I can only add one object at a time right?

And thanks it seems to work now ;)

[Sierra]

You may add multiple objects using .addAll(...) from the ArrayList.

[lo2]

Ok well I have another question:

I have this method where I want to be able to determine if two cells are equal, this means to determine if they have the same position. I have then written this piece of code where I both use instanceof and casting to make sure that my object is of the type position and then make it of the type position, but it does not seem to work for some reason. Here is my code:

 

public class Position {

	private int column;
	private int row;
	
	public Position (final int column, final int row) 
	{
		this.column = column;
		this.row = row;
	}
	
		public int getColumn()
		{
			return column;
		}
		
		public int getRow()
		{
			return row;
		}

		public boolean equals(final Object other) {
      if(other instanceof Position) {
      Position position = (Position) other;
        return ((column == other.getColumn()) && (row == other.getRow()));
		}
    else {
      return false;
      }
    }

I get this error code, in fact I get an error code for both of the get. methods:

error:
cannot find symbol
return ((column == other.getColumn()) && (row == other.getRow()));
^
symbol: method getRow()
location: variable other of type Object

[wsaryada]

Your code should be:

return ((column == position.getColumn()) && (row == position.getRow()))

Because "other" type is java.lang.Object it will never find the getRow() method in there.