scala Quick Start series [abstract]

        Benpian scala fast as twenty-four series of blog entry, for everyone to bring about an abstract class content.

        

---

Abstract class

        And Java languages, scala can also be defined in the abstract class.

definition

        If a member of a class defined in the current class does not contain complete, it is an abstract class .

Incomplete definition of two situations:

1. No method Method body ( abstract method )
2. Uninitialized variables ( abstract field )

        The definition of abstract classes and Java, in front of the class plus the abstract keyword.

Abstract method

Examples

• Design of classes, inheritance represents the above-described FIG.
• Each form has its own method of seeking area, but different methods of calculating the area of ​​a different shape

step:

1. Creates a Shape abstract class, an abstract method to add an area for calculating the area.
2. Square square create a class that inherits from the Shape, which has a side length of the primary builder, and area calculation method implemented.
3. Create a rectangle class inherits from the Shape, which has a length and width of the main structure, to achieve a method to calculate the area.
4. Creating a circular class inherits from the Shape, which has a radius of the primary constructor, and to achieve a method to calculate the area.
5. Write the main method, respectively, to create a square, rectangular, circular object, and print area thereof.

Reference Code:

---

Abstract field

        In the scala, abstract fields may be defined. If a member variable is not initialized, we think it is abstract.

Syntax

example

1. Create a Person abstract class with a String abstract field WHO_AM_I
2. Creating a Student class inherits from the Person class, rewrite WHO_AM_I field, initialized to students
3. Creating a Student class inherits from the Person class, rewrite WHO_AM_I field, initialized to students
4. Add the main method, create an instance of Student / Policeman, respectively, and then were printed WHO_AM_I

Reference Code

---

        This issue of content sharing on here, like little friends remember a point like this, continued attention to the next one will bring you yo ~Anonymous inner classesIntroduction, stay tuned 9 (1> ◡ <1) 6