封装一个类MyStock存放在cn.com.my包中，这个类包括：

1 一个名为id的int数据字段表示股票代码；P96第四题

等等等

主函数中具体的数据可以自行修改

 import cn.com.my.MyStock; public class NewMain { public static void main(String[] args) { double a; MyStock MyStock = new MyStock(); MyStock.previousPrice = 12.34; MyStock.currentPrice =12.45; MyStock.setid(123214); MyStock.setname("烟带" ); System.out.println("id:"+MyStock.getid()); System.out.println(MyStock.getname()); System.out.printf("股票的变化：" + "%.5f", MyStock.getPriceChange()); System.out.print('%'); } } 

在MyStack类中

 package cn.com.my; public class MyStock { int id; String name; public double previousPrice; public double currentPrice; public int getid() { return id; } public void setid(int id) { this.id = id; } public String getname() { return name; } public void setname(String name) { this.name = name; } public double getpreviousPrice() { return previousPrice; } public void setpreviousPrice(double previousPrice) { this.previousPrice = previousPrice; } public double getcurrentPrice() { return currentPrice; } public void setcurrentPrice(double currentPrice){ this.currentPrice=currentPrice; } public double getPriceChange() { double a; a = ((currentPrice - previousPrice) / previousPrice) * 100; return (a); } } 

一个有特定代码和名称的股票构造方法就是上述中构造中的多个get和set，set是用来从主函数中获得数据的，get是把得到的数据输出到主函数中的。在主函数中若要直接引用MyStock中的数据的话，需要把MyStock中的数据public。

2.封装一个类MyAccount类存放在cn.com.my包中：

主函数与1中类似稍微修改模拟银行开户过程

import cn.com.my.MyAccount; public class NewMain { public static void main(String[] args) { System.out.println("正在创建新账户……"); MyAccount a = new MyAccount(); a.setId(4123); a.setBalance(0); a.setAnnualRate(0.1); System.out.println("账户ID为：" + a.getId()); System.out.println("账户余额为：" + a.getBalance()); System.out.println("开户日期为：" + a.getDateCreated()); System.out.println("月利率为" + a.getAnnualRate() + "%"); a.deposit(123); System.out.println("您当前的余额为" + a.getBalance()); a.withDarw(2); System.out.println("您当前的余额为" + a.getBalance()); } }

而在MyAccount中具体的代码如下

 package cn.com.my; import java.util.Date; public class MyAccount { public MyAccount(){ } public MyAccount(int a){ this.id=1; this.balance=9; } int id=0; double balance; double annualRate=0; Date dateCreated=new Date(); public void setId(int id){ this.id=id; } public int getId(){ return id; } public void setBalance(double balance){ this.balance=balance; } public double getBalance(){ return balance; } public void setAnnualRate(double annualRate){ this.annualRate=annualRate; } public double getAnnualRate(){ return annualRate; } public Date getDateCreated(){ return dateCreated; } public double getMonthRate(){ return 0.25; } public double withDarw(int n){ balance=balance-n; return balance; } public double deposit(int n){ balance=balance+n; return balance; } } 

封装一个MyPoint存放在cn.com.my包中，这个类包括：

1.两个double类型的私有坐标点x和y

等等等

主程序为

import cn.com.my.MyPoint; public class NewMain { public static void main(String[] args) { MyPoint first = new MyPoint(); MyPoint second= new MyPoint(1); System.out.println("MyPoint类型的两个点的距离为："+MyPoint.distance(first, second)); MyPoint b1=new MyPoint(); MyPoint b2=new MyPoint(); b1.setX(1.1); b1.setY(1.2); b2.setX(2.3); b2.setY(2.5); System.out.printf("指定x和y坐标的两个点之间的距离为："+MyPoint.distance(b1.getX(), b1.getY(), b2.getX(), b2.getY())); } }

MyPoint类里面

package cn.com.my; public class MyPoint { public MyPoint(){ x=0; y=0; } public MyPoint(int a){ x=1.1; y=2.1; } double x,y; public void setX(double x){ this.x=x; } public double getX(){ return x; } public void setY(double y){ this.y=y; } public double getY(){ return y; } public static double distance(MyPoint a,MyPoint b){ double x=(a.x-b.x)*(a.x-b.x); double y=(a.y-b.y)*(a.y-b.y); double c=Math.sqrt(x+y); return c; } public static double distance(double x1,double y1,double x2,double y2){ double x=(x1-x2)*(x1-x2); double y=(y1-y2)*(y1-y2); double c=Math.sqrt(x+y); return c; } } 

Beautiful

整个Java要比C更加美