[LintCode] Shape Factory

Problem

Factory is design pattern in common usage. Implement a ShapeFactory that can generate correct shape.

Example

ShapeFactory sf = new ShapeFactory();
Shape shape = sf.getShape("Square");
shape.draw();
 ----
|    |
|    |
 ----

shape = sf.getShape("Triangle");
shape.draw();
   /\
  /  \
 /____\

shape = sf.getShape("Rectangle");
shape.draw();
  ----
 |    |
  ----

Note

这道题考了interface & implementation & override，具体概念如下：

Interface: A Java interface is a bit like a class, except that it can only contain method signatures and fields, which is saying that it cannot contain any implementation of the methods. You can use interface to achieve polymorphism.

Implementation: To declare a class that implements an interface, you have to include an implements clause in the class definition. Your class can implement more than one interface.

Overriding: If subclass provides the specific/close implementation of the method that has been provided by one of its parent class, it is known as method overriding.

除此之外，还需要注意正则表达式的写法。

Solution

interface Shape {
    void draw();
}

class Rectangle implements Shape {
    @Override
    public void draw() {
        System.out.println(" ----"); 
        System.out.println("|    |");
        System.out.println(" ----");    
    }
}

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

class Triangle implements Shape {
    @Override
    public void draw() {
        System.out.println("  /\\"); 
        System.out.println(" /  \\");
        System.out.println("/____\\");
    }
}

public class ShapeFactory {
    public Shape getShape(String shapeType) {
        if (shapeType.equalsIgnoreCase("Rectangle")) return new Rectangle();
        else if (shapeType.equalsIgnoreCase("Square")) return new Square();
        else if (shapeType.equalsIgnoreCase("Triangle")) return new Triangle();
        return null;
    }
}