1.1(设计模式）工厂模式

 工厂模式：

工厂模式通过工厂创建对象，用户无需注意内部细节，只需要调用工厂类，

将需要创建的类名称传递给工厂即可。

采用工程类创建，最后返回的是接口类型，所以只用关心接口，不用关心接口的具体实现类。

Shape接口

public interface Shape {
    public void draw();
}

实现Shape接口的具体类：

public class Circle implements Shape{

    @Override
    public void draw() {
        System.out.println("draw circle");
    }  
}

public class Rectangle implements Shape{

    @Override
    public void draw() {
        System.out.println("draw rectangle");
    }
}

public class Square implements Shape{

    @Override
    public void draw() {
        System.out.println("draw square");
    }
}

ShapeFactory工厂：

public class ShapeFactory {
    public Shape getShape(String shape) {//传递图像字符串，根据字符串判断并实例化对应对象
        if("circle".equals(shape)) {
            return new Circle();
        }else if("rectangle".equals(shape)) {
            return new Rectangle();
        }else if("square".equals(shape)) {
            return new Square();
        }
        return null;
    } 
}

Main调用ShapeFactory实例化对象

public class Main {
    public static void main(String[] args) {
        ShapeFactory shapeFactory = new ShapeFactory();
        Shape circle = shapeFactory.getShape("circle"); 
        circle.draw();
    }
}

运行结果：
draw circle

ShapeFatory中采用if else，当工厂中类多了后采用if else不易于扩展，且代码结构复杂不好分析。

故将图形用枚举类型代替，结合switch代替if else.

图形枚举

public enum ShapeEnum {
    CIRCLE,RECTANGLE,SQUARE
}

ShapeFactory

public class ShapeFactory {
    public Shape getShape(ShapeEnum shape) {
        switch(shape) {
        case CIRCLE:       return new Circle();
        case RECTANGLE:    return new Rectangle();
        case SQUARE:    return new Square();
        default : try {//没有找到指定类型则抛出ClassNotFound异常
                throw new ClassNotFoundException();
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return null;
    } 
}

Main

public class Main {
    public static void main(String[] args) {
        ShapeFactory shapeFactory = new ShapeFactory();
        Shape circle = shapeFactory.getShape(ShapeEnum.CIRCLE); 
        circle.draw();
    }
}

运行结果：
draw circle

参考资料：

http://www.runoob.com/design-pattern/factory-pattern.html