SimpleFactoryPattern（23种设计模式之一）

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设计模式六大原则（1）：单一职责原则
设计模式六大原则（2）：里氏替换原则
设计模式六大原则（3）：依赖倒置原则
设计模式六大原则（4）：接口隔离原则
设计模式六大原则（5）：迪米特法则
设计模式六大原则（6）：开闭原则

SimpleFactoryPattern，UML抽象图百度找，代码实现如下

使用简单工厂模式设计一个可以创建不同几何形状(如圆形、矩形和三角形等)的绘图工具，每个几何图形都要有计算面积area()和计算周长gride()两个方法

抽象产品类

package SimpleFactoryPattern;
public interface Product {
    public float area();
    public float gride();
}

具体产品类

package SimpleFactoryPattern.ConcreteProduct;
import SimpleFactoryPattern.Product;
public class Circular implements Product{
    private float r;
    public Circular(float r) {
        this.r = r;
    }
    @Override
    public float area() {
        return 3.14f * r * r;
    }

    @Override
    public float gride() {
        return 3.14f * 2 * r;
    }
}

package SimpleFactoryPattern.ConcreteProduct;
import SimpleFactoryPattern.Product;
public class Rectangle implements Product {
    private float width;
    private float height;
    public Rectangle(float width, float height) {
        this.width = width;
        this.height = height;
    }
    @Override
    public float area() {
        return width * height * 1.0f;
    }
    @Override
    public float gride() {
        return (width + height) * 2.0f;
    }

}

package SimpleFactoryPattern.ConcreteProduct;
import SimpleFactoryPattern.Product;
public class Triangle implements Product {
    private float a;
    private float b;
    private float c;
    public Triangle(float a, float b, float c) {
        this.a = a;
        this.b = b;
        this.c = c;
    }
    @Override
    public float area() {
        float p = (a+b+c)/2.0f;
        return (float) Math.sqrt(p*(p-a)*(p-b)*(p-c));
    }
    @Override
    public float gride() {
        return a+b+c;
    }

}

简单工厂类

package SimpleFactoryPattern;
import java.util.Scanner;
import SimpleFactoryPattern.ConcreteProduct.Circular;
import SimpleFactoryPattern.ConcreteProduct.Rectangle;
import SimpleFactoryPattern.ConcreteProduct.Triangle;
public class Creator {
    Scanner scan = new Scanner(System.in);
    Product product=null;
    public Product create(String type) {        //工厂里的制造方法一定是静态吗！？
        if("圆".equals(type)){
            return new Circular(scan.nextFloat());
        }else if("矩形".equals(type)){
            return new Rectangle(scan.nextFloat(),scan.nextFloat());
        }else if("三角形".equals(type)){
            return new Triangle(scan.nextFloat(),scan.nextFloat(),scan.nextFloat());
        }else{
            return product;
        }
    }
}

测试类

package SimpleFactoryPattern;
public class Test {
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Product product = new Creator().create("");
        if(product==null){
            System.out.println("请填写工厂条件");
        }else{
            System.out.println(product.area());
        }
    }

}

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别嫌弃我没写注释，这个代码很简单，注释省略，嘿嘿。