Prototype Mode - Prototype

Prototype Mode - Prototype

Create more objects of the same type by duplicating (clone, copy) an object of a specified type.

Product interface

We will use the prototype pattern to create objects, and these objects are abstracted as Product

Product also provides a copy method createClone(). It inherits the Cloneable interface.

Note: The createClone() method here is not inherited from Cloneable. There is no method declared in Cloneable. Cloneable is just an interface for marking.

public interface Product extends Cloneable {
    void use(String str);

    Product createClone();
}

UnderlinePen class

This is the implementation class of the Product interface, the underscore class. 

After passing a string to a specific underscore class, it will print out the string and the underscore

public class UnderLinePen implements Product {
    /**
     * underscore character
     */
    private char underLineChar;

    public UnderLinePen(char ch) {
        this.underLineChar = ch;
    }

    /**
     * After passing in str, it will print str and underscore
     */
    @Override
    public void use(String str) {
        System.out.println("\"" + str + "\"");
        System.out.print(" ");
        for (int i = 0; i < str.getBytes().length; i++) {
            System.out.print(underLineChar);
        }
        System.out.println("");
    }

    /**
     * return a clone
     */
    @Override
    public Product createClone() {
        try {
            return (Product) this.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace ();
            return null;
        }
    }
}

UnderLinePenManager类

For unified management of products, he is responsible for registration and cloning

public class UnderLinePenManager {
    /**
     * All kinds of pens are registered here, unified management
     */
    private static final HashMap<String, Product> PENS = new HashMap<>();

    /**
     * Registration pen
     */
    public static void register(String name, Product pen) {
        PENS.put(name, pen);
    }

    /**
     * Take a pen from the registry HashMap with name as the key, and then clone a new one to return
     */
    public static Product createPen(String name) {
        return PENS.get(name).createClone();
    }
}

Main

This class is used to run tests

public class Main {
    static {
        /**
         * Register various pens to Manager for unified management
         */
        UnderLinePenManager.register("wave-line"  , new UnderLinePen('~'));
        UnderLinePenManager.register("bee-line"   , new UnderLinePen('_'));
        UnderLinePenManager.register("dotted-line", new UnderLinePen('.'));
    }

    public static void main(String[] args) {
        // Every time you need a certain pen, just clone a copy based on the existing pen
        // Take out a wavy pen
        Product anotherPen1 = UnderLinePenManager.createPen("wave-line");
        // print with a wavy pen
        anotherPen1.use("hello world");
    }
}