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