抽象工厂模式与印刷

Question

学习更多的设计模式--特别是在这里，我正在研究抽象的工厂模式。我试图输出“接收1头1页脚1”全部在一行，但我似乎只能通过displayName方法一次输出。连接它们的最佳方法是什么？抽象类中的toString方法？任何指示都将不胜感激。以下是我的课程：

public abstract class AbstractSalesReceiptFactory {
    public abstract AbstractReceipt createReceipt();
    public abstract AbstractHeader createHeader();
    public abstract AbstractFooter createFooter();


}

public abstract class AbstractReceipt {
    public abstract void displayName(AbstractReceipt a);

}

public abstract class AbstractHeader {
    public abstract void displayName(AbstractHeader a);

}

public abstract class AbstractFooter {
    public abstract void displayName(AbstractFooter a);

}

public class ConcreteReceipt1 extends AbstractSalesReceiptFactory{

    public AbstractReceipt createReceipt() {
        return new Receipt1();
    }
    public AbstractHeader createHeader() {
        return new Header1();
    }


    public AbstractFooter createFooter() {
        return new Footer1();
    }

    private ConcreteReceipt1() {}

    public String displayName() {
        return "Receipt1";
    }

    private static ConcreteReceipt1 instance = null;

    public static ConcreteReceipt1 getInstance() {
        instance = new ConcreteReceipt1();
        return instance;
    }

}

public class ConcreteReceipt2 extends AbstractSalesReceiptFactory{

    public AbstractReceipt createReceipt() {
        return new Receipt1();
    }

    public AbstractHeader createHeader() {
        return new Header1();
    }


    public AbstractFooter createFooter() {
        return new Footer1();
    }

    private ConcreteReceipt2() {
    }

    public String displayName() {
        return "Receipt2";
    }
    private static ConcreteReceipt2 instance = null;

    public static ConcreteReceipt2 getInstance() {
        instance = new ConcreteReceipt2();
        return instance;
    }


}

public class Footer1 extends AbstractFooter{
    public void displayName(AbstractFooter a) {
        System.out.println("Footer 1");
    }
}

public class Footer2 extends AbstractFooter{
    public void displayName(AbstractFooter a) {
        System.out.println("Footer 2");
    }
}

public class Header1 extends AbstractHeader{
    public void displayName(AbstractHeader a) {
        System.out.println("Header 1");
    }

}

public class Header2 extends AbstractHeader{
    public void displayName(AbstractHeader a) {
        System.out.println("Header 2");
    }

}

public class Receipt1 extends AbstractReceipt{
    public void displayName(AbstractReceipt a) {
        System.out.println("Receipt 1");
    }

}

public class Receipt2 extends AbstractReceipt{
    public void displayName(AbstractReceipt a) {
        System.out.println("Receipt 2");
    }

}

我的主修班：

public class Client {

    private static AbstractReceipt ar;
    private static AbstractHeader ah;
    private static AbstractFooter af;

    public Client(AbstractSalesReceiptFactory factory) {
        ar = factory.createReceipt();
        ah = factory.createHeader();
        af = factory.createFooter();
    }

    public void run() {
        ar.displayName(ar);
        ah.displayName(ah);
        af.displayName(af);
    }

    public static void main (String [] args) {
        AbstractSalesReceiptFactory receipt1 = ConcreteReceipt1.getInstance();

        Client c1 = new Client(receipt1);
        c1.run();
    }
}

Answer 1

implementations.

• You可以在现有的displayName方法中将System.out.println更改为System.out.print，

1. 可以重写toString方法，但是您可能希望保留toString，并使用displayName.
2. Another简单的方法获得您希望的输出，首先在抽象类中更新displayName的签名，这样它就返回String而不是void (并且不带参数)。例如，

    public abstract class AbstractReceipt {
        public abstract String displayName();
    }

然后更新所有具体类中的实现，以返回所需的显示名称，而不是直接打印。

    public class Receipt1 extends AbstractReceipt{
        public String displayName() {
            return "Receipt 1";
        }
    }

最后，更新run方法以执行System.out.println。

    public void run() {
        System.out.println(
            String.format( "%s %s %s", ar.displayName(), ah.displayName(),  af.displayName() )
        );
    }

但是，您的请求更多地与Java /O相关，而不是设计模式。您只需使用控制台输出来提供模式实现的简单验证。