java设计模式之建造者模式学习
1概述
建造者模式(BuilderPattern)主要用于“分步骤构建一个复杂的对象”,在这其中“分步骤”是一个稳定的算法,而复杂对象的各个部分则经常变化。因此,建造者模式主要用来解决“对象部分”的需求变化。这样可以对对象构造的过程进行更加精细的控制。
2示例
以生产手机为例,每个手机分为屏幕Screen、CPU、Battery。现在要生产两种手机,苹果机和三星。
苹果:
packageorg.scott.builder.before.use;
importjava.util.ArrayList;
importjava.util.List;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicclassApplePhone{
List<String>parts=newArrayList<String>();
publicvoidcreateCPU(){
parts.add("CUP:Qualcomm");
}
publicvoidcreateScreen(){
parts.add("SCREEN:JDI");
}
publicvoidcreateBattery(){
parts.add("BATTERY:DeSai");
}
publicvoidshow(){
System.out.print("产品部件信息:");
for(Stringpart:parts){
System.out.print(part+"\t");
}
}
}
三星:
packageorg.scott.builder.before.use;
importjava.util.ArrayList;
importjava.util.List;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicclassSamsungPhone{
List<String>parts=newArrayList<String>();
publicvoidcreateCPU(){
parts.add("CUP:MTK");
}
publicvoidcreateScreen(){
parts.add("SCREEN:Samsung");
}
publicvoidcreateBattery(){
parts.add("BATTERY:DeSai");
}
publicvoidshow(){
System.out.print("产品部件信息:");
for(Stringpart:parts){
System.out.print(part+"\t");
}
}
}
测试客户端:
是不是发现个问题?那就是生产手机的每一道工序都是一样的,确切的说是工序名称一样,只是具体的每个工序的处理不同,工序是不变的,就这么几步,每道工序的具体处理是变化的,由此,我们可以把不变的抽取出来,以“不变应万变”,将变化的,交给具体的产品来做。 首先来个Phone的接口: importjava.util.ArrayList; /** publicvoidshow(){ 苹果手机类: } 三星手机类: } 再定义个生产步骤的接口Builder: 苹果手机的Builder: @Override @Override @Override } 三星手机的Builder: @Override @Override @Override } 指导具体生产手机的Director: 最后写个测试类: privatestaticBuilderiPhoneBuilder=newApplePhoneBuilder(); } 运行结果: 这里的两个Phone实体类是空的,如果是这种情况,那么它们可以省略掉,如果Phone接口也可以被省略掉,最终剩下的就只有Director、Builder、和具体的Bulider实现类。并且,ApplePhone类和SamsungPhone类是有关系的两个类,它们不同的手机品牌,如果遇到两个或多个没有太多关系的类,公共的接口Phone就没有存在的必要,但是这时候,那么Builder接口的规定的getPhone()方法的返回值怎么确定呢? 无论返回值类型是ApplePhone还是SamsungPhone,都会产生问题,因为返回结果的类型不统一。此时,可以将Phone定义成一个空接口(不包含任何方法的接口),再让这些没有相互关系的具体产品类都去实现这个接口,那么Builder接口里面规定的getPhone()方法的返回值类型依然是Phone类型,就解决问题了。不过这种情况下,也就没有使用Builder模式的必要了。
packageorg.scott.builder.before.use;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicclassBuilerTest{
privatestaticApplePhoneiphone=newApplePhone();
privatestaticSamsungPhonesamPhone=newSamsungPhone();
publicstaticvoidmain(Stringargs[]){
iphone.createCPU();
iphone.createScreen();
iphone.createBattery();
iphone.show();
samPhone.createCPU();
samPhone.createScreen();
samPhone.createBattery();
samPhone.show();
}
}
具体怎么做?这回的Builder模式派上用场了。
packageorg.scott.builder.after.use;
importjava.util.List;
*@authorScott
*@version2013-11-20
*@description
*/
publicabstractclassPhone{
protectedList<String>parts=newArrayList<String>();
publicvoidadd(Stringpart){
parts.add(part);
}
System.out.print("产品部件信息:");
for(Stringpart:parts){
System.out.print(part+"\t");
}
}
}
packageorg.scott.builder.after.use;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicclassApplePhoneextendsPhone{
packageorg.scott.builder.after.use;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicclassSamsungPhoneextendsPhone{
packageorg.scott.builder.after.use;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicinterfaceBuilder{
publicvoidbuildCPU();
publicvoidbuildScreen();
publicvoidbuildBattery();
publicPhonegetPhone();
}
packageorg.scott.builder.after.use;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicclassApplePhoneBuilderimplementsBuilder{
privatePhonephone=newApplePhone();
@Override
publicvoidbuildCPU(){
phone.add("CUP:Qualcomm");
}
publicvoidbuildScreen(){
phone.add("SCREEN:JDI");
}
publicvoidbuildBattery(){
phone.add("BATTERY:DeSai");
}
publicPhonegetPhone(){
returnphone;
}
packageorg.scott.builder.after.use;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicclassSamsungPhoneBuilderimplementsBuilder{
privatePhonephone=newSamsungPhone();
@Override
publicvoidbuildCPU(){
phone.add("CUP:MTK");
}
publicvoidbuildScreen(){
phone.add("SCREEN:Samsung");
}
publicvoidbuildBattery(){
phone.add("BATTERY:DeSai");
}
publicPhonegetPhone(){
returnphone;
}
packageorg.scott.builder.after.use;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicclassDirector{
privateBuilderbuilder;
publicDirector(Builderbuilder){
this.builder=builder;
}
publicvoidconstruct(){
builder.buildCPU();
builder.buildScreen();
builder.buildBattery();
}
}
packageorg.scott.builder.after.use;
/**
*@authorScott
*@version2013-11-20
*@description
*/
publicclassBuilderTest{
privatestaticBuildersamPhoneBuilder =newSamsungPhoneBuilder();
publicstaticvoidmain(String[]args){
Directordirector=newDirector(iPhoneBuilder);
director.construct();
Phonephone=iPhoneBuilder.getPhone();
System.out.println("iphone");
phone.show();
director=newDirector(samPhoneBuilder);
director.construct();
phone=samPhoneBuilder.getPhone();
System.out.println("\nsamSung");
phone.show();
}
iphone
产品部件信息:CUP:Qualcomm SCREEN:JDI BATTERY:DeSai
samSung
产品部件信息:CUP:MTK SCREEN:Samsung BATTERY:DeSai
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