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;    }}