设计模式之工厂模式

工厂模式（Factory Pattern）是 Java 中最常用的设计模式之一。这种类型的设计模式属于创建型模式，它提供了一种创建对象的最佳方式。

定义一个创建对象的接口，让其子类自己决定实例化哪一个工厂类，工厂模式使其创建过程延迟到子类进行。

首先，创建一个接口Shape.java

public interface Shape {
public void draw();
}

然后，创建子类Circle.java及Square.java

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

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

接着，创建一个工厂类ShapeFactory.java

public class ShapeFactory {
public <T> T getByClass(Class clazz) {
try {
return (T) Class.forName(clazz.getName()).newInstance();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

}

最后，创建测试类Test.java

public class Test {
public static void main(String[] args) {
ShapeFactory shapeFactory = new ShapeFactory();
Circle circle = (Circle) shapeFactory.getShapeByClass(Circle.class);
circle.draw();
Square square = (Square) shapeFactory.getShapeByClass(Square.class);
square.draw();
}
}

另外，如果是抽象工厂的话，创建一个抽象工厂类AbstractFactory.java

public abstract class AbstractFactory {
public abstract <T> T getByClass(Class clazz);
}

然后，创建实现类AbstractShapeFactory.java

public class AbstractShapeFactory extends AbstractFactory {
@Override
public <T> T getByClass(Class clazz) {
try {
T cls = (T) Class.forName(clazz.getName()).newInstance();
return cls;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}

最后，测试类Test.java

public class Test {
public static void main(String[] args) {
AbstractFactory shapeFactory = new AbstractShapeFactory();
Circle circle = (Circle) shapeFactory.getByClass(Circle.class);
circle.draw();
Square square = (Square) shapeFactory.getByClass(Square.class);
square.draw();
}
}