//股票1
class shares1{
    public void buy1(){
        System.out.println("股票1買入");
    };

    public void sell1(){
        System.out.println("股票1賣出");
    };
}
//股票2
class shares2{
    public void buy2(){
        System.out.println("股票2買入");
    };

    public
 
 void sell2(){
        System.out.println("股票2賣出");
    };
}
//股票3
class shares3{
    public void buy3(){
        System.out.println("股票3買入");
    };

    public void sell3(){
        System.out.println("股票3賣出");
    };
}

public static void main(String[] args) {
    shares1 shares1 = new
 
 shares1();
    shares2 shares2 = new shares2();
    shares3 shares3 = new shares3();
    shares1.buy1();
    shares2.buy2();
    shares3.buy3();

    shares1.sell1();
    shares2.sell2();
    shares3.sell3();
}

//
 
基金
class Fund {
    private Shares1 shares1;
    private Shares2 shares2;
    private Shares3 shares3;

    public Fund(Shares1 shares1, Shares2 shares2, Shares3 shares3) {
        this.shares1 = shares1;
        this.shares2 = shares2;
        this.shares3 = shares3;
    }

    public void buy(){
        shares1.buy1();
        shares2.buy2();
        shares3.buy3();
    }

    public void sell(){
        shares1.sell1();
        shares2.sell2();
        shares3.sell3();
    }
}

public static void main(String[] args) {
    Fund fund = new Fund(new Shares1(), new Shares2(), new Shares3());
    fund.buy();
    fund.sell();
}

總結：