继承原则：子类只继承超类中非private的成员变量 *隐藏原则(Hiding)：子类的成员变量和超类的成员变量同名时，超类的成员变量被隐藏。
若想使用超类的成员变量用super.  
class Person{        
String name;
                         int age;        
                       String address;        
void setPerson(String name,int age,String address)
{
this.name=name;
this.address=address;
this.age=age;                        
}        
void print()
{                
System.out.println("woshiperson");
} }
class Student extends Person{        
String department;        
void setStudent(String name,int age,String address,String department){                 this.name=name;
this.age=age;
this.address=address;
this.department=department;
}        
void print(){
System.out.println("woshistudent");
} }
public class Person_ex {        
public static void main(String arge[])       
{
Person p=new Person();
p.setPerson("tom",21,"121");
Student s=new Student();
s.setStudent("john",22,"336","computer");
/*System.out.println(p.name+"  "+p.age+"  "+p.address);System.out.println(s.name+"  "+s.age+"  "+s.address);*/
s.print();        
}
}

继承原则：子类只继承超类中非private的成员变量 *隐藏原则(Hiding)：子类的成员变量和超类的成员变量同名时，超类的成员变量被隐藏。
若想使用超类的成员变量用super.  
class Person{        
String name;
                         int age;        
                       String address;        
void setPerson(String name,int age,String address)
{
this.name=name;
this.address=address;
this.age=age;                        
}        
void print()
{                
System.out.println("woshiperson");
} }
class Student extends Person{        
String department;        
void setStudent(String name,int age,String address,String department){                 this.name=name;
this.age=age;
this.address=address;
this.department=department;
}        
void print(){
System.out.println("woshistudent");
} }
public class Person_ex {        
public static void main(String arge[])       
{
Person p=new Person();
p.setPerson("tom",21,"121");
Student s=new Student();
s.setStudent("john",22,"336","computer");
/*System.out.println(p.name+"  "+p.age+"  "+p.address);System.out.println(s.name+"  "+s.age+"  "+s.address);*/
s.print();        
}
}