橋接模式-Bridge

橋梁模式的用意是"將抽象化(Abstraction)與實現化(Implementation)脫耦, 將"類的功能層次結構" 與 "類的實現層次結構"分離為兩個獨立的類層次結構.

類的實現層次接口

DisplayImpl接口

public interface DisplayImpl {
    void rawOpen();

    void rawPrint();

    void rawClose();
}

StringDisplayImpl類

public class StringDisplayImpl implements DisplayImpl {
    private String string;
    private int width;

    public StringDisplayImpl(String string) {
        this.string = string;
        this.width = string.getBytes().length;
    }

    public void rawOpen() {
        printLine();
    }

    public void rawPrint() {
        System.out.println("|" + string + "|");
    }

    public void rawClose() {
        printLine();
    }

    private void printLine() {
        System.out.print("+");
        for (int i = 0; i < width; i++) {
            System.out.print("-");
        }
        System.out.println("+");
    }
}

類的功能層次結構

Display類

在功能實現的最高層上關聯了DisplayImpl接口, 在此處進行了橋接.

public class Display {
    private DisplayImpl impl;

    public Display(DisplayImpl impl) {
        this.impl = impl;
    }

    public void open() {
        impl.rawOpen();
    }

    public void print() {
        impl.rawPrint();
    }

    public void close() {
        impl.rawClose();
    }

    public final void display() {
        open();
        print();
        close();
    }
}

CountDisplay類

在Display類的基礎上, 進行功能上的擴展. 擴展一個multiDisplay()功能.

public class CountDisplay extends Display {
    public CountDisplay(DisplayImpl impl) {
        super(impl);
    }

    public void multiDisplay(int times) {
        open();
        for (int i = 0; i < times; i++) {
            print();
        }
        close();
    }
}

Main

用於測試運行

public class Main {
    public static void main(String[] args) {
        Display d1 = new Display(new StringDisplayImpl("Hello, China."));
        Display d2 = new CountDisplay(new StringDisplayImpl("Hello, World."));
        CountDisplay d3 = new CountDisplay(new StringDisplayImpl("Hello, Universe."));
        d1.display();
        d2.display();
        d3.display();
        d3.multiDisplay(5);
    }
}

橋接模式-Bridge(Java實現)