Builder

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Builder模式的使用情景

相同的方法, 不同的执行顺序, 产生不同的事件结果
多个部件或零件, 都可以装配到一个对象中, 但是产生的运行结果又不相同
产品类比较复杂, 或者产品类中的调用顺序不同产生了不同的作用.
当初始化一个对象特别复杂, 如参数多, 且很多参数都具有默认值.

Builder模式的整体构造

产品类

abstract class Computer {    protected String mBoard;    protected String mDisplay;    protected String mOS;    protected Computer(){    }    public void setBoard(String board){        mBoard=board;    }    public void setDisplay(String display){        mDisplay=display;    }    public abstract void setOS();    @Override    public String toString() {        return "Computer [mBoard="+ mBoard+", mDisplay="+mDisplay+", mOS="+mOS+"]";    }}class Macbook extends Computer{    protected Macbook(){    }    @Override    public void setOS() {        mOS="Mac OS X 10.10";    }}

Builder类

//抽象Builder类abstract class Builder{    public abstract void buildBoard(String board);    public abstract void buildDispaly(String display);    public abstract void buildOS();    public abstract Computer create();}//具体Builder类class MacbookBuilder extends Builder{    private Computer mComputer=new Macbook();    @Override    public void buildBoard(String board) {        mComputer.setBoard(board);    }    @Override    public void buildDispaly(String display) {        mComputer.setDisplay(display);    }    @Override    public void buildOS() {        mComputer.setOS();    }    @Override    public Computer create() {        return mComputer;    }}

导演类

导演类起到封装的作用, 避免高层模块深入到建造者内部的实现类

class Direcotr{    Builder mBuilder=null;    public Direcotr(Builder builder){        mBuilder=builder;    }    public void construct(String board,String dispaly){        mBuilder.buildBoard(board);        mBuilder.buildDispaly(dispaly);        mBuilder.buildOS();    }}

public class BuildTest{    public static void main(String[] args){        Builder builder=new MacbookBuilder();        Direcotr pcDirector=new Direcotr(builder);        pcDirector.construct("intel","retina");        StdOut.println("Computer Info : "+builder.create().toString());    }}

忽略Director类

在开发过程中, 可以忽略Director类, 直接使用Builder来进行对象的组装, 可以使用setter方法进行链式调用.
new Builder().setA("A").setB("B").create()

public class BuildTest {    public static void main(String[] args){        ConcreteProductA A= (ConcreteProductA)new A_Buider().setArg_1("aa")                                        .setArg_2("bb").create();        StdOut.print(A);    }}abstract class abstractProduct{    protected String arg_1;    protected String arg_2;    protected abstract void setArg_1(String arg_1);    protected abstract void setArg_2(String arg_2);    @Override    public String toString() {        return "arg_1: "+arg_1+", arg_2: "+arg_2;    }}class ConcreteProductA extends abstractProduct{    protected void setArg_1(String arg_1){        this.arg_1=arg_1;    }    protected void setArg_2(String arg_2){        this.arg_2=arg_2;    }}abstract class Builder {    public abstract Builder setArg_1(String arg_1);    public abstract Builder setArg_2(String arg_2);    public abstract abstractProduct create();}class A_Buider extends Builder{    private ConcreteProductA mConcreteProductA=new ConcreteProductA();    @Override    public Builder setArg_1(String arg_1) {        mConcreteProductA.setArg_1(arg_1);        return this;    }    @Override    public Builder setArg_2(String arg_2) {        mConcreteProductA.setArg_2(arg_2);        return this;    }    @Override    public abstractProduct create(){        return mConcreteProductA;    }}

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