抽象类 需要用abstract 修饰类和接口

abstract class Person{String address;String name;abstract public void eat();abstract public void drink();public void printInfo(){System.out.println("name= " + name);}}
class Student extends Person{public void eat(){System.out.println("学生吃饭");}public void drink() {// TODO Auto-generated method stubSystem.out.println("学生喝水");}
}
public class Test {public static void main(String[] args) {Student t = new Student();t.eat();t.drink();}
}

接口需要interface修饰，更强调行为

interface Xinwei{abstract void eat();abstract void drink();
}class man implements Xinwei{public void eat() {// TODO Auto-generated method stubSystem.out.println("人吃饭");}public void drink() {// TODO Auto-generated method stubSystem.out.println("人喝水");	}	
}class dog implements Xinwei{public void eat() {// TODO Auto-generated method stubSystem.out.println("狗吃饭");}public void drink() {// TODO Auto-generated method stubSystem.out.println("狗喝水");	}	
}public class Test {public static void main(String[] args) {new man().drink();new dog().drink();}
}