Java 反射之工厂模式

一.简单工厂模式

//接口
package Factory;

public interface Fruit {
public void eat(); //吃
}

//实现接口类
package Factory;

public class Apple implements Fruit{

public Apple() {
// TODO Auto-generated constructor stub
}

public void eat() {
// TODO Auto-generated method stub
System.out.println("吃苹果！");
}

}
package Factory;

public class Banana implements Fruit{

public Banana() {
// TODO Auto-generated constructor stub
}

public void eat() {
// TODO Auto-generated method stub
System.out.println("吃香蕉！");
}

}

package Factory;

public class Orange implements Fruit{

public Orange() {
// TODO Auto-generated constructor stub
}

public void eat() {
// TODO Auto-generated method stub
System.out.println("吃橘子");
}

}

//工厂类
package Factory;

public class Factory {

public Factory() {
// TODO Auto-generated constructor stub

}
public static Fruit getInstance(String className){
if("apple".equals(className))
return new Apple(); //返回一个对象
if("banana".equals(className))
return new Banana();
if("orange".equals(className))
return new Orange();
return null;
}

}

//主方法
package Factory;

import java.util.Scanner;

public class FactoryTest {

public FactoryTest() {
// TODO Auto-generated constructor stub
}

public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner scanner=new Scanner(System.in);
String className=scanner.nextLine();//输入想要创建对象的名字
Fruit f=Factory.getInstance( className); //调用并接收
f.eat();
}

}

运行结果：







这个工厂类是最简单的工厂类，可以体会到工厂模式的设计思想，但是每次想添加一个类都需要更改大量的代码，所以后来演变了一个更方便使用的工厂模式，利用反射机制创建对象，从而减少对代码的修改。

如果想再添加一个葡萄类

package Factory;

public class Grape implements Fruit{

public Grape() {
// TODO Auto-generated constructor stub
}

@Override
public void eat() {
// TODO Auto-generated method stub
System.out.println("吃葡萄！");
}

}

//要在返回对象那多加一个创建葡萄类

package Factory;

public class Factory {

public Factory() {
// TODO Auto-generated constructor stub

}
public static Fruit getInstance(String className){
if("apple".equals(className))
return new Apple();
if("banana".equals(className))
return new Banana();
if("orange".equals(className))
return new Orange();
if("grape".equals(className))
return new Grape(); //这里还要修改
return null;
}

}

运行结果：



这样对代码的修改量会增大，这只是一个简单的工厂模式，若果放到一个项目当中那修改的代码量远远比这个要多很多。

二.反射之工厂模式

//接口
package fanshe;

public interface Fruit {
public void eat(); //吃

}

//实现接口的类
package fanshe;

public class Apple implements Fruit {

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blic Apple() {
// TODO Auto-generated constructor stub
}

public void eat() {
// TODO Auto-generated method stub
System.out.println("吃苹果~！");
}

}

package fanshe;

public class Banana implements Fruit{

public Banana() {
// TODO Auto-generated constructor stub
}

public void eat() {
// TODO Auto-generated method stub
System.out.println("吃香蕉~！");
}

}

package fanshe;

public class Orange implements Fruit {

public Orange() {
// TODO Auto-generated constructor stub
}

public void eat() {
// TODO Auto-generated method stub
System.out.println("吃橘子~！");
}

}

//工厂类
package fanshe;

public class Factory {

public Factory() {
// TODO Auto-generated constructor stub
}
public static Fruit getInstance(String className)
{
/*if("orange".equals(className))
return new Orange();
return null;*/
Fruit fruit=null;
try {
fruit=(Fruit) Class.forName(className).newInstance();//创建对象

} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return fruit;

}

}

//主方法
package fanshe;

import java.util.Scanner;

public class FactortDemo {

public FactortDemo() {
// TODO Auto-generated constructor stub
}

public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner scanner=new Scanner(System.in);
String className=scanner.nextLine(); //输入想要创建类的名字
Fruit fruit=Factory.getInstance("fanshe."+className);
fruit.eat();
}

}

运行结果：







如果再想添加一个葡萄类直接添加类就可以了，不用再修改其他代码，减少了代码的修改量

package fanshe;

public class Grape implements Fruit{

public Grape() {
// TODO Auto-generated constructor stub
}

@Override
public void eat() {
// TODO Auto-generated method stub
System.out.println("吃葡萄~！");
}

}

运行结果：