从零自学Java-8.创建第一个对象

1.创建对象；
2.使用属性描述对象；
3.确定对象的行为；
4.合并对象；
5.从其他对象继承；
6.转换对象和其他类型的信息。

程序NewRoot2：计算输入数的算数平方根并输出

 package com.jsample;

 public class NewRoot2 {
     public static void main(String[] args){
         int number = 100;
         if (args.length > 0){
             number = Integer.parseInt(args[0]);
         }
         System.out.println("The square root of "
                 + number
                 + " is "
                 + Math.sqrt(number)
         );
     }

输出：

The square root of 169 is 13.0

程序ModemTester：测试下属四个class的功能

 package com.jsample;

 public class ModemTester {
     public static void main(String[] args){
         CableModem surfBoard = new CableModem();
         DslModem gateway = new DslModem();
         AcousticModem acoustic = new AcousticModem();
         surfBoard.speed = 500000;
         gateway.speed = 400000;
         acoustic.speed = 300;
         System.out.println("Trying the cable modem:");
         surfBoard.displaySpeed();
         surfBoard.connect();
         System.out.println("Trying the DSL modem");
         gateway.displaySpeed();
         gateway.connect();
         System.out.println("Trying the acoustic modem");
         acoustic.displaySpeed();
         acoustic.connect();
         System.out.println("Closing all modems");
         surfBoard.disconnect();
         gateway.disconnect();
         acoustic.disconnect();
     }
 }

下属class：Modem

 package com.jsample;

 public class Modem {
     int speed;

     public void displaySpeed(){
         System.out.println("Speed: " + speed);
     }

     public void disconnect(){
         System.out.println("Disconnecting to the Internet");
     }
 }

下属class：CableModem

 package com.jsample;

 public class CableModem extends Modem{
     String method = "cable connecttion";

     public void connect(){
         System.out.println("Connecting to the Internet");
         System.out.println("Using a " + method);
     }
 }

下属class：DslModem

 package com.jsample;

 public class DslModem extends Modem{
     String method = "DSL phone connection";

     public void connect(){
         System.out.println("Connecting to the Internet");
         System.out.println("Using a " + method);
     }
 }

下属class：AcousticModem

 package com.jsample;

 public class AcousticModem extends Modem{
     String method = "acoustic connection";

     public void connect(){
         System.out.println("Connecting to the Internet");
         System.out.println("Using a " + method);
     }
 }

输出：
Trying the cable modem:
Speed: 500000
Connecting to the Internet
Using a cable connecttion
Trying the DSL modem
Speed: 400000
Connecting to the Internet
Using a DSL phone connection
Trying the acoustic modem
Speed: 300
Connecting to the Internet
Using a acoustic connection
Closing all modems
Disconnecting to the Internet
Disconnecting to the Internet
Disconnecting to the Internet