桥接模式-Bridge

桥梁模式的用意是"将抽象化(Abstraction)与实现化(Implementation)脱耦, 将"类的功能层次结构" 与 "类的实现层次结构"分离为两个独立的类层次结构.

类的实现层次接口

DisplayImpl接口

public interface DisplayImpl {    void rawOpen();    void rawPrint();    void rawClose();}

StringDisplayImpl类

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("+");    }}

类的功能层次结构

Display类

在功能实现的最高层上关联了DisplayImpl接口, 在此处进行了桥接.

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类

在Display类的基础上, 进行功能上的扩展. 扩展一个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

用于测试运行

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);    }}