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工厂模式主要是避免new所带来的依赖，这样可以在应用直接替换对象而不用修改。

实现要点：

1.创建一个Product的类或者接口，Product的子类实现这个接口（或继承这个类）；

2.创建一个Factory的类或者接口，Factory的子类实现这个接口（或继承这个类），实现建造对象的方法。

public interface Shape {void draw();
}
public class Circle implements Shape {@Overridepublic void draw() {System.out.println("draw circle");}
}
public class Square implements Shape{public void draw() {System.out.println("draw square");}
}
public interface ShapeFactory {public Shape make(String shapeName) throws Exception;}
public class ShapeFactoryImpl implements ShapeFactory{@Overridepublic Shape make(String shapeName) throws Exception {if (shapeName.equals("Circle")) {return new Circle();} else if (shapeName.equals("Square")) {return new Square();} else {throw new Exception("Shape Factory can't create " + shapeName);}}
}public class Test {/*** @param args*/public static void main(String[] args) {ShapeFactory shapeFactory = new ShapeFactoryImpl();Shape circleShape;try {circleShape = shapeFactory.make("Circle");circleShape.draw();} catch (Exception e) {e.printStackTrace();}Shape squareShape;try {squareShape = shapeFactory.make("Square");squareShape.draw();} catch (Exception e) {e.printStackTrace();}}
}

Java 类库中的使用范例：

java.util.Calendar – getInstance()
java.util.Calendar – getInstance(TimeZone zone)
java.util.Calendar – getInstance(Locale aLocale)
java.util.Calendar – getInstance(TimeZone zone, Locale aLocale)

java.text.NumberFormat – getInstance()
java.text.NumberFormat – getInstance(Locale inLocale)