Java study notes the abstract classes and interfaces

Abstract class (abstract)

Overview abstract class : a class is abstract modification indicates that this class is an abstract class,  define their own methods but not implementation, to achieve the offspring

Abstract methods :    a method to be abstract modification indicates that this method is an abstract method, abstract method is no method body        

Features :

1, there must be a class abstract methods abstract class, an abstract method of the abstract class does not necessarily have. Abstract class has abstract methods 0-N

2, abstract class can not be instantiated, meaning not new an abstract class

3, those who inherit the abstract class, must implement the abstract class method is an abstract class or their own

4, constructors and static methods can not be abstract

The following is an example :

Abstract class Person

. 1  public  abstract  class the Person {
 2      // private attributes gender 
. 3      Private String Sex;
 . 4      // has parameters configured 
. 5      public the Person (String Sex) {
 . 6          the this .sex = Sex;
 . 7      }
 . 8      // abstract method 
. 9      public  abstract  void doSomething ();
 10      
. 11 }

Subclass Student

. 1  public  class Student the extends the Person {
 2  
. 3      Private String name; // name 
. 4      Private  int Age; // Age
 5      // there is a reference configuration 
. 6      public   Student ( int Age) {
 . 7          Super ( "M" );
 . 8          the this .age = Age;
 . 9      }
 10      public Student ( int Age, String name) {
 . 11          the this (Age);
 12 is          the this .name = name;
13 is      }
 14      public  void doSomething () {
 15          System.out.println ( "I am a student class implements the abstract method doSomething" );
 16      }
 . 17  
18 is }

Subclass Teacher

. 1  public  class Teacher the extends the Person {
 2      public Teacher (String Sex) {
 . 3          Super (Sex);
 . 4      }
 . 5  
. 6      public  void doSomething () {
 . 7          System.out.println ( "I am a teacher class implements the abstract method doSomething" );
 8      }
 . 9     
10 }

Test class Text

1 public class Text {
2 
3     public static void main(String[] args) {
4         Person p=new Student(12);
5         p.doSomething();
6         Person p1=new Teacher("男");
7         p1.doSomething();
8     }
9 }

Console output is:

I am a student class implements the abstract method doSomething
I am a teacher class implements the abstract method doSomething

Interface (interface)