无涯教程-Java 工厂模式工厂模式是Java中最常用的设计模式之一，这种设计模式属于创建模式，因为该模式提供了创建对

工厂模式是Java中最常用的设计模式之一，这种设计模式属于创建模式，因为该模式提供了创建对象的最佳方法之一。

工厂模式实例

无涯教程将创建一个 Shape 接口和实现 Shape 接口的具体类。下一步将定义工厂类 ShapeFactory 。

FactoryPatternDemo ，演示类将使用 ShapeFactory 获得 Shape 对象。它将( Circle/Rectangle/Square )传递给 ShapeFactory 以获取所需的对象类型。

第1步 - 创建一个接口。

Shape.java

public interface Shape {
   void draw();
}

第2步 - 创建实现相同接口的具体类。

Rectangle.java

public class Rectangle implements Shape {
@Override
public void draw() {
System.out.println("Inside Rectangle::draw() method.");
}
}

Square.java

public class Square implements Shape {
@Override
public void draw() {
System.out.println("Inside Square::draw() method.");
}
}

Circle.java

public class Circle implements Shape {
@Override
public void draw() {
System.out.println("Inside Circle::draw() method.");
}
}

第3步 - 创建一个Factory以根据给定的信息生成具体类的对象。

ShapeFactory.java

public class ShapeFactory {
//use getShape method to get object of type shape 
public Shape getShape(String shapeType){
if(shapeType == null){
return null;
}
if(shapeType.equalsIgnoreCase("CIRCLE")){
return new Circle();
  </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">else</span><span class="pln"> </span><span class="kwd">if</span><span class="pun">(</span><span class="pln">shapeType</span><span class="pun">.</span><span class="pln">equalsIgnoreCase</span><span class="pun">(</span><span class="str">"RECTANGLE"</span><span class="pun">)){</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">Rectangle</span><span class="pun">();</span><span class="pln">
     
  </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">else</span><span class="pln"> </span><span class="kwd">if</span><span class="pun">(</span><span class="pln">shapeType</span><span class="pun">.</span><span class="pln">equalsIgnoreCase</span><span class="pun">(</span><span class="str">"SQUARE"</span><span class="pun">)){</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">Square</span><span class="pun">();</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">
  
  </span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">null</span><span class="pun">;</span><span class="pln">

}
}

第4步 - 使用工厂通过传递诸如类型信息来获取具体类的对象。

FactoryPatternDemo.java

public class FactoryPatternDemo {
public static void main(String[] args) {
ShapeFactory shapeFactory=new ShapeFactory();
  </span><span class="com">//获取一个 Circle 对象并调用它的 draw 方法。</span><span class="pln">
  </span><span class="typ">Shape</span><span class="pln"> shape1</span><span class="pun">=</span><span class="pln">shapeFactory</span><span class="pun">.</span><span class="pln">getShape</span><span class="pun">(</span><span class="str">"CIRCLE"</span><span class="pun">);</span><span class="pln">

  </span><span class="com">//调用Circle的draw方法</span><span class="pln">
  shape1</span><span class="pun">.</span><span class="pln">draw</span><span class="pun">();</span><span class="pln">

  </span><span class="com">// 获取一个 Rectangle 对象并调用它的 draw 方法。</span><span class="pln">
  </span><span class="typ">Shape</span><span class="pln"> shape2</span><span class="pun">=</span><span class="pln">shapeFactory</span><span class="pun">.</span><span class="pln">getShape</span><span class="pun">(</span><span class="str">"RECTANGLE"</span><span class="pun">);</span><span class="pln">

  </span><span class="com">// 调用 Rectangle 的 draw 方法</span><span class="pln">
  shape2</span><span class="pun">.</span><span class="pln">draw</span><span class="pun">();</span><span class="pln">

  </span><span class="com">//get an object of Square and call its draw method.</span><span class="pln">
  </span><span class="typ">Shape</span><span class="pln"> shape3</span><span class="pun">=</span><span class="pln">shapeFactory</span><span class="pun">.</span><span class="pln">getShape</span><span class="pun">(</span><span class="str">"SQUARE"</span><span class="pun">);</span><span class="pln">

  </span><span class="com">// 调用正方形的draw方法</span><span class="pln">
  shape3</span><span class="pun">.</span><span class="pln">draw</span><span class="pun">();</span><span class="pln">

}
}

第5步 - 验证输出。

Inside Circle::draw() method.
Inside Rectangle::draw() method.
Inside Square::draw() method.

无涯教程-Java 工厂模式

工厂模式实例

参考链接