public class Student 
{ 
  private String name; 
  private int age; 
  private String college; 
  public Student() 
  { 
    age = 20; 
  } 
  public Student(String name) 
  { 
    this();//can not be call Student,only use this() method. 
    this.name = name; 
    System.out.println("this student name is "+name); 
  } 
  public Student(String name,String college) 
  { 
    this(name);//C++中可以直接用Student(name)调用其他构造函数 
    this.college = college; 
    System.out.println("this student name is "+name+" college is "+college);     
  } 
 
  public Student upgrade() 
  { 
    age++; 
    return this; 
  } 
 
  public void print() 
  { 
    System.out.println("name is: "+name 
        +" age is: "+age 
        +" college is: "+college); 
  } 
 
  public static void main(String[] args) 
  { 
    Student student1 = new Student("linc"); 
    Student student2 = new Student("linc","shenyang college"); 
    student2.upgrade().print(); 
  } 
} 

public class ClassLeader extends Student 
{ 
  private String duty; 
  public ClassLeader() 
  { 
    duty = "class monitor"; 
  } 
  public ClassLeader(String duty,String name,String college) 
  { 
    super(name,college); 
    this.duty = duty; 
  } 
 
  public void print() 
  { 
    super.print(); 
    System.out.println("duty is " + duty); 
  } 
   
  public static void main(String[] args)  
  {  
    ClassLeader leader = new ClassLeader("life","linc","shenyang"); 
  leader.print(); 
  }  
   
} 

D:\workspace\Java\project261\super>javac -d . *java 
 
D:\workspace\Java\project261\super>java ClassLeader 

this student name is linc 
this student name is linc college is shenyang 
name is: linc age is: 20 college is: shenyang 
duty is life