Java, the keyword abstract (abstract classes and abstract methods)

/ * 
* Abstract using keywords 
* 1.abstract: abstract 
* 2.abstract can be used to modify the structure: Class, Method 
* 
* 3. Modified abstract class: abstract 
*> such can not be instantiated 
*> abstract class there must be a constructor, to facilitate call when the subclass is instantiated (involving: subclass object instantiated whole process) 
*> development, are provided subclasses of the abstract class so that the child class object is instantiated, are supposed to do 
* 
* 
* 4. abstract modification methods: method abstract 
*> the only way to abstract method declarations, no method body 
*> contains the abstract class methods, it must be an abstract class. Conversely, there may be no abstract class abstract methods. 
*> If a subclass overrides After all the abstract methods of the parent class, the subclass is instantiated only 
* if not all of the subclasses of the abstract parent class for reprogramming This abstract class is a subclass, abstract modification required 
* / 
public class AbstractTest { 
   public static void main (String [] args) { 
      
      // Once the abstract Person class, it can not be instantiated 
// new new Person Person P1 = (); 
// p1.eat () ; 
      
   } 
}

abstract class Creature{
   public abstract void breath();
}

abstract class Person extends Creature{
   String name;
   int age;
   
   public Person(){
      
   }
   public Person(String name,int age){
      this.name = name;
      this.age = age;
   }
   
   //不是抽象方法：
// public void eat(){
//    
// }
   //抽象方法
   public abstract void eat();
   
   public void walk(){
      System.out.println("人走路");
   }
   
   
}


class Student extends Person{
   
   public Student(String name,int age){
      super(name,age);
   }
   public Student(){
   }
   
   EAT void public () { 
      System.out.println ( "Student more nutritious foods"); 
   } 

   @Override 
   public void Breath () { 
      System.out.println ( "student should not haze of the fresh air" ); 
   } 
}