Java ninth job: Chapter 9 contains three examples and chapter 9 of Chapter 9

Java ninth job: Chapter 9 contains three examples and chapter 9 of Chapter 9

Job 1:

Example 9.1 create a circle class and obtain the perimeter and area based on the circle radius

Package com. swift; // abstract method composition class, which encapsulates attributes and methods in public class Circle {// two aspects: one is the field also called attribute, and the other is the method, also known as the implemented function private double radius; // constructor, with parameters to construct public Circle (double radius) {this. radius = radius;} // method overload. Different parameters // constructor. public Circle () {this. radius = 1;} // Method for Calculating the circular area public double getArea () {return radius * Math. PI;} // Method for Calculating the circumference public double getPerimeter () {return 2 * Math. PI * radius;} public void setRadius (double newRadius) {this. radius = newRadius ;}}

Circle display

package com.swift;public class DemoCircle {    public static void main(String[] args) {        Circle circle1=new Circle();        double area=circle1.getArea();        System.out.println(area);        Circle circle2=new Circle(10);        System.out.println(circle2.getArea());        System.out.println(circle1.getPerimeter());        System.out.println(circle2.getPerimeter());        double ridius=10;        double areaCircle=Math.PI*ridius*ridius;        System.out.println(areaCircle);        circle2.setRadius(5);        System.out.println(circle2.getArea());    }}

Job 2:

Combine the classes of the above two circles into one class and implement the same function.

package com.swift;public class SimpleCircle {    private double radius;    public SimpleCircle() {        this.radius=1;    }    public SimpleCircle(double radius){        this.radius=radius;    }    public double getArea() {        // TODO Auto-generated method stub        return Math.PI*radius*radius;    }    public double getPerimeter() {        return 2*Math.PI*radius;    }        public static void main(String[] args) {        SimpleCircle cir1=new SimpleCircle();        System.out.println("The area of the circle of radius "+cir1.radius+" is "+cir1.getArea());        SimpleCircle cir2=new SimpleCircle(10);        System.out.println("The area of the circle of radius "+cir2.radius+" is "+cir2.getArea());    }}

Job 3:

Example 9.3 create a TV set and implement the functions of FM channels and sound adjustment

Package com. swift; public class TV {public int channel = 1; public int volumeLevel = 1; public boolean on = false; public TV () {} public void turnOn () {on = true; system. out. println ("the TV has been turned on. ");} Public void turnOff () {on = false; System. out. println (" the TV has been disabled. ");} Public int getChannel () {return channel;} public void setChannel (int channel) {if (on) {System. out. println ("the TV is on. You can start to set up the TV. "); If (channel> = 1 & channel <= 120) {this. channel = channel; System. out. println ("channel has been adjusted to" + channel + "");} else {System. out. println ("the channel you want to call does not exist. ") ;}} Else {System. out. println ("the TV cannot be redeployed when it is turned off") ;}} public int getVolumeLevel () {return volumeLevel;} public void setVolumeLevel (int volumeLevel) {if (on) {System. out. println ("TV on, adjustable sound size"); if (volumeLevel> = 1 & volumeLevel <= 7) {this. volumeLevel = volumeLevel; System. out. println ("the sound size is set to" + volumeLevel + "size") ;}} else {System. out. println ("audio cannot be played when the TV is turned off") ;}} public void channelUp () {if (on & channel <120) {channel ++ ;}} public void channelDown () {if (on & channel> 1) {channel -- ;}} public void volumeUp () {if (on & volumeLevel <7) {volumeLevel ++ ;}} public void volumeDown () {if (on & volumeLevel> 1) {volumeLevel --;}}}

Test TV class

package com.swift;public class TestTV {    public static void main(String[] args) {//        TV tv1=new TV();//        tv1.turnOff();//        tv1.setChannel(30);//        tv1.setVolumeLevel(3);                TV tv2=new TV();        tv2.turnOn();        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);        tv2.channelUp();        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);        tv2.channelUp();        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);        tv2.channelUp();        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);        tv2.volumeUp();        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);        tv2.volumeUp();        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);        tv2.volumeUp();        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);                    }}