/**Toss coin test that allow the you guess the upside as many times as you wish. When exit, the system would give you a list of information about your guesses.*/
import java.io.*;
public class TossCoin {
 public static void main(String[]args)
 {
  String input=null;
  long seed=System.currentTimeMill

接口类只可以继承接口类的，例如Student是一个类，而“public interface CollegeStudentInterface extends Student”就是错误的。如果要写一个CollegeStudent的接口只能先把Student接口化，然后将CollegeStudentInterface继承它。

/**An interface for a class of students.*/
public interface StudentInterface
{
 /**

·实验说明：模拟一个银币，此银币有两个面。方法为‘抛银币’，银币顶面、底面随机向上。抛两银币各50次，并显示两银币顶面向上次数和哪个银币顶面次数较多。

·代码：

import java.util.*;
public class GenericCoin {
 private int front;
 private int back;
 
 GenericCoin(){ 
  front=1;
  back=0;
 }//end constructor
 
 

/** a person with name and age*/
public class Person {
 private Name name;
 private int age;
 
 public Person(){
  name=null;
  age=0;
 }//end default constructor
 
 public Person(Name personName,int personAg

·实验说明：创建了Student类，数据域中声明了类型为一个先前创建的Name类的私有变量。main方法中使用两种创建Student对象的方法。

·代码
public class Student {
   private Name fullName;
   private String id;//学号
  
   public Student(){
    fullName=new Name();
    id="";

· 实验

·作用：计数器，实现每次加一或减一运算

·代码：
public class Counter {
//post:increase or decrease cnt by 1
private int cnt;
public Counter(){
 cnt=0;
}//end default constructor
public void inc(){
 ++cnt;
}//end inc 
public void dec(){