如何在我的股票投资组合中增加头寸，当前遇到有关不兼容类型的错误，无法将其转换为int或String

Question

I'm having trouble adding the stock to the portfolio. I have tried without new Stock, with just stock instead of stock.tickersymbol and it still doesn't work. What would I need to change to add the stock and quantity to the positions?

The error I am getting is

error: incompatible types: Stock cannot be converted to String

error: incompatible types: Stock cannot be converted to int positions.add(new Stock(stock.tickerSymbol), quantity);

  positions.add(new Stock(stock), quantity);

I am trying to get this line working.

positions.add(new Stock(stock.tickerSymbol), quantity);

public boolean buy(Stock stock, int quantity, double price) {
    double total = price * quantity;

    if (cash >= total) {
        cash -= total;
        positions.add(new Stock(stock.tickerSymbol), quantity);
        return true;
    }

    return false;        
}

The following is my minimum viable code

import java.io.*;
import java.util.*;
import java.util.stream.*;
import org.junit.*;
import org.junit.runner.*;
import static org.junit.Assert.*;

class Stock {

  public String tickerSymbol;

  public Stock(String tickerSymbol) {
    this.tickerSymbol = tickerSymbol;
  }

}

class Position {

  public Stock stock;
  public int quantity;

  public Position(Stock stock, int quantity) {
    this.stock = stock;
    this.quantity = quantity;
  }

}

class Portfolio {



  public double cash;
  public List<Position> positions;


  public Portfolio(double cash, List<Position> positions) {
    this.cash = cash;
    this.positions = new ArrayList<>(positions);
  }

  /*
  If the buy is viable (sufficient cash), executes it and returns true,
  else returns false
  */
  public boolean buy(Stock stock, int quantity, double price) {



    double total = price * quantity;

    if (cash >= total)
    {
      cash -=total;
      positions.add(new Stock(stock.tickerSymbol), quantity);
      return true;

    }
    return false;

  }




}

Answer 1

The buy method needs to be part of the Portfolio class if it is going to access the positions variable (I'm going to go ahead and assume it is...). Then you need to define a new Position to add to the positions list, as that is a List of the object Position, not Stock:

positions.add(new Position(stock, quantity));