Simple Factory
Prerequisites:
未優化前
以下是一個訂購Pizza與制作Pizza的流程。
制作Pizza
Pizza
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public abstract class Pizza {
private String name;
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
// 不同的pizza準備的材料不同，由不同的pizza去覆寫
public abstract void prepare();
// 相同的作法就統一寫
public void bake() {
System.out.println("放進烤箱");
}
public void cut() {
System.out.println("把pizza切片");
}
public void box() {
System.out.println("pizza裝進盒子");
}
}
CheesePizza
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public class CheesePizza extends Pizza{
@Override
public void prepare() {
System.out.println(getName() + "有:起士");
}
}
TomatoPizza
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public class TomatoPizza extends Pizza{
@Override
public void prepare() {
System.out.println(getName() + "有:蕃茄");
}
}
訂購pizza
OrderPizza
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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class OrderPizza {
public OrderPizza() {
Pizza pizza = null;
String pizzaType;
do {
pizzaType = getType();
if (pizzaType.equals("tomato")) {
pizza = new TomatoPizza();
pizza.setName("瑪格麗特pizza");
} else if (pizzaType.equals("cheese")) {
pizza = new CheesePizza();
pizza.setName("起士pizza");
} else {
// 輸入其它的字就離開迴圈
break;
}
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
} while (true);
}
private String getType() {
try {
BufferedReader strin = new BufferedReader(new InputStreamReader(System.in));
System.out.println("input pizza type:");
String str = strin.readLine();
return str;
} catch (IOException e) {
e.printStackTrace();
return "";
}
}
}
main 主程式
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public class PizzaStore {
public static void main(String[] args) {
OrderPizza orderPizza = new OrderPizza();
}
}
input pizza type:
cheese
起士pizza有:起士
放進烤箱
把pizza切片
pizza裝進盒子
input pizza type:
tomato
瑪格麗特pizza有:蕃茄
放進烤箱
把pizza切片
pizza裝進盒子
input pizza type:
a
優化
以上的問題是，為什麼產生pizza的程式碼在訂購的流程中？
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if (pizzaType.equals("tomato")) {
pizza = new TomatoPizza();
pizza.setName("瑪格麗特pizza");
} else if (pizzaType.equals("cheese")) {
pizza = new CheesePizza();
pizza.setName("起士pizza");
} else {
// 輸入其它的字就離開迴圈
break;
}
把產生pizza的程式碼放入工廠的類別中，由Pizza工廠來生產pizza，只需要給它pizzaType的參數。
SimpleFactory
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public class SimpleFactory {
public Pizza createPizza(String pizzaType) {
Pizza pizza = null;
if (pizzaType.equals("tomato")) {
pizza = new TomatoPizza();
pizza.setName("瑪格麗特pizza");
} else if (pizzaType.equals("cheese")) {
pizza = new CheesePizza();
pizza.setName("起士pizza");
}
return pizza;
}
}
OrderPizza類別增加設置Pizza工廠
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private SimpleFactory factory;
public void setFactory(SimpleFactory factory) {
this.factory = factory;
}
OrderPizza增加order()的方法，只負責取得pizza的種類、事前準備prepare()、烤、切、裝盒子。
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public void order() {
Pizza pizza = null;
String pizzaType;
do {
pizzaType = getType();
// 產生pizza
pizza = factory.createPizza(pizzaType);
// 跳離迴圈
if (pizza == null) break;
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
} while (true);
}
類別圖如下:
setFactory是聚合的關係，所以是用空白菱型，請見類別圖文章。
完整的OrderPizza
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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class OrderPizza {
private SimpleFactory factory;
public void setFactory(SimpleFactory factory) {
this.factory = factory;
}
public void order() {
Pizza pizza = null;
String pizzaType;
do {
pizzaType = getType();
pizza = factory.createPizza(pizzaType);
if (pizza == null) break;
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
} while (true);
}
public OrderPizza() {
}
private String getType() {
try {
BufferedReader strin = new BufferedReader(new InputStreamReader(System.in));
System.out.println("input pizza type:");
String str = strin.readLine();
return str;
} catch (IOException e) {
e.printStackTrace();
return "";
}
}
}