设计一个Stock类和DividendStock类 - 编写了一个表示拥有股票情况的Stock类，这里给出了一个简化版，去掉了对参数的合法性的检查等细节：

/**
 *作者：魏宝航
 *2020年11月22日,下午15:40
 */
public class test {
    public static void main(String[] args) {
            DividendStock oracle = new DividendStock("Oracle");
            oracle.purchase(200,32);
            oracle.purchase(350,40);
            oracle.payDividend(2.8);
            System.out.println(oracle.toString());
            System.out.println(oracle.getProfit(50));
    }
}
class Stock {
    private String symbol;
    private int totalShares;
    private double totalCost;
        public Stock(){
        }
    // Initializes a new Stock with no shares purchased.
    public Stock(String theSymbol) {
        symbol = theSymbol;
        totalShares = 0;
        totalCost = 0.0;
    }
    // Returns the total shares purchased of this stock.
    public int getTotalShares() {
        return totalShares;
    }
    // Returns the total profit or loss earned on this stock.
    public double getProfit(double currentPrice) {
        double marketValue = totalShares * currentPrice;
        return marketValue - totalCost;
    }
    // Records purchase of the given shares at the given price.
    public void purchase(int shares, double pricePerShare) {
        totalShares += shares;
        totalCost += shares * pricePerShare;
    }
    @Override
    public String toString() {
        return "Stock [symbol=" + symbol + ", totalShares=" + totalShares + ", totalCost=" + totalCost + "]";
    }
//getter和setter方法自己补充
        public void setTotalCost(double totalCost) {
                this.totalCost = totalCost;
        }
        public void setTotalShares(int totalShares) {
                this.totalShares = totalShares;
        }
        public void setSymbol(String symbol) {
                this.symbol = symbol;
        }
        public double getTotalCost() {
                return totalCost;
        }
        public String getSymbol() {
                return symbol;
        }
}
class DividendStock extends Stock{
        double dividents;
        public DividendStock(String symbol){
                super(symbol);
        }
        @Override
        public double getProfit(double currentPrice) {
                return super.getProfit(currentPrice)+dividents;
        }
        public void payDividend(double amountPerShare){
                dividents=super.getTotalShares()*amountPerShare;
        }
        @Override
        public String toString() {
                return "Stock [symbol=" + super.getSymbol() + ", totalShares=" + super.getTotalShares() + ", totalCost=" + super.getTotalCost() +", dividents="+dividents+ "]";
        }
}