1、设计四个类,分别是:(知识点:抽象类及抽象方法)(1)Shape表示图形类,有面积属性area、周长属性per,颜色属性color,有两个构造方法(一个是默认的、一个是为颜色赋值的),还有3个抽象方法,分别是:getArea计算面积、getPer计算周长、showAll输出所有信息,还有一个求颜色的方法getColor。(2)2个子类:    1)Rectangle表示矩形类,增加两个属性,Width表示长度、height表示宽度,重写getPer、getArea和showAll三个方法,另外又增加一个构造方法(一个是默认的、一个是为高度、宽度、颜色赋值的)。    2)Circle表示圆类,增加1个属性,radius表示半径,重写getPer、getArea和showAll三个方法,另外又增加两个构造方法(为半径、颜色赋值的)。 (3)一个测试类PolyDemo,在main方法中,声明创建每个子类的对象,并调用2个子类的showAll方法。package study;public abstract class Shape {    double area;    double per;//perimeter    String color;    public Shape() {            }    public Shape(String color) {        super();        this.color = color;    }    public abstract void getArea();    public abstract void getPer();    public abstract void showAll();    public String getColor() {        return color;    }    public void setColor(String color) {        this.color = color;    }        }package study;public class Rectangle extends Shape{    double length;    double width;    public Rectangle() {                }    public Rectangle(double a, double b,String c) {        super();        length=a;        width=b;        color=c;    }    @Override    public void getArea() {        // TODO Auto-generated method stub        area=length*width;    }    @Override    public void getPer() {        // TODO Auto-generated method stub        per=(length+width)*2;    }    @Override    public void showAll() {        // TODO Auto-generated method stub        System.out.println("颜色是"+color+"面积是"+area+"周长是"+per);            }    }package study;public class Circle extends Shape{    double radius;        public Circle() {            }    public Circle(double radius,String a) {        super();        this.radius = radius;        color=a;    }        @Override    public void getArea() {        // TODO Auto-generated method stub        area=radius*radius*3.14;    }    @Override    public void getPer() {        // TODO Auto-generated method stub        per=2*radius*3.14;    }    @Override    public void showAll() {        // TODO Auto-generated method stub        System.out.println("颜色是"+color+"半径是"+radius+"面积是"+area+"周长是"+per);    }}package study;public class PolyDemo {    public static void main(String[] args) {        // TODO Auto-generated method stub        Rectangle r=new Rectangle(3,4,"月白");        r.getArea();        r.getPer();        r.showAll();        Circle c=new Circle(2.0,"橙黄");        c.getArea();        c.getPer();        c.showAll();    }}2、Cola公司的雇员分为以下若干类:(知识点:多态)(1) ColaEmployee :这是所有员工总的父类,属性:员工的姓名,员工的生日月份。Ÿ 方法:getSalary(int month) 根据参数月份来确定工资,如果该月员工过生日,则公司会额外奖励100 元。(2) SalariedEmployee :    ColaEmployee 的子类,拿固定工资的员工。Ÿ 属性:月薪(3) HourlyEmployee :ColaEmployee 的子类,按小时拿工资的员工,每月工作超出160 小时的部分按照1.5 倍工资发放。Ÿ 属性:每小时的工资、每月工作的小时数(4) SalesEmployee :ColaEmployee 的子类,销售人员,工资由月销售额和提成率决定。Ÿ 属性:月销售额、提成率(5) 定义一个类Company,在该类中写一个方法,调用该方法可以打印出某月某个员工的工资数额,写一个测试类TestCompany,在main方法,把若干各种类型的员工放在一个ColaEmployee 数组里,并单元出数组中每个员工当月的工资。package Cola;public abstract class ColaEmployee {    String name;    int birthmonth;        public ColaEmployee() {            }    public ColaEmployee(String name, int birthmonth) {        this.name = name;        this.birthmonth = birthmonth;    }    abstract double getSalary(int month) ;}package Cola;public class SalariedEmployee extends ColaEmployee{    double salar;        public SalariedEmployee() {            }    public SalariedEmployee(String name, int birthmonth,double salar) {        super(name,birthmonth);        this.salar=salar;    }    @Override     double getSalary(int month) {        if(month==birthmonth) {            salar+=100;        }        return salar;    }}package Cola;public class HourlyEmployee extends ColaEmployee{    double shourly;    double hours;    public HourlyEmployee() {        super();        // TODO Auto-generated constructor stub    }    public HourlyEmployee(String name, int birthmonth,double shourly,double hours) {        super(name, birthmonth);        // TODO Auto-generated constructor stub        this.shourly=hours;        this.hours=hours;    }    double getSalary(int month) {        if(hours>160.0) {            shourly=(160.0*shourly)+(hours-160.0)*(shourly*1.5);        }else {            shourly=hours*shourly;        }        if(month==birthmonth) {            shourly+=100.0;            return shourly;        }else {            return shourly;        }    }}package Cola;public class SalesEmployee extends ColaEmployee{    double smonthly;    double rate;         public SalesEmployee() {        super();        // TODO Auto-generated constructor stub    }    public SalesEmployee(String name, int birthmonth, double smonthly,double rate) {        super(name, birthmonth);        // TODO Auto-generated constructor stub        this.smonthly=smonthly;        this.rate=rate;    }    public double getSalary(int month) {         smonthly=smonthly+smonthly*rate;         if(month==birthmonth) {             smonthly+=100;             return smonthly;         }else {             return smonthly;         }     }}package Cola;public class Company{    public static void getSalary(ColaEmployee a,int month) {        System.out.println(month+"月"+a.name+"员工"+"的月薪是"+a.getSalary(month)+"元。");    }}package Cola;public class TestCompany {    public static void main(String[] args) {        // TODO Auto-generated method stub        ColaEmployee [] b=new ColaEmployee[6];        b[0]=new SalesEmployee("王伟", 4, 10000, 5);        b[1]=new SalesEmployee("刘美",8,12000,5);        b[2]=new SalariedEmployee("张钧", 11, 20000);        b[3]=new SalariedEmployee("高晟", 2, 23000);        b[4]=new HourlyEmployee("季澊", 9, 200, 168);        b[5]=new HourlyEmployee("沈复",5,300,170);        for (ColaEmployee a:b) {            Company.getSalary(a,5);        }    }}3、利用接口实现动态的创建对象:(知识点:接口 )(1)创建4个类    1苹果    2香蕉    3葡萄    4园丁(2)在三种水果的构造方法中打印一句话.    以苹果类为例    class apple    {        public apple()        {            System.out.println(“创建了一个苹果类的对象”);    }    }(3)类图如下:(4)要求从控制台输入一个字符串,根据字符串的值来判断创建三种水果中哪个类的对象。    运行结果如图:        package study;public interface Fruit {    }package study;public class apple implements Fruit {    public apple() {        super();        // TODO Auto-generated constructor stub        System.out.println("创建了一个苹果类的对象");    }    }package study;public class Banana  implements Fruit {    public Banana() {        super();        // TODO Auto-generated constructor stub        System.out.println("创建了一个香蕉类的对象");    }    }package study;public class Pear  implements Fruit {    public Pear() {        super();        // TODO Auto-generated constructor stub        System.out.println("创建了一个梨类的对象");    }    }package study;import java.util.Scanner;public class Garder {     public void creater() {             System.out.println("请输入你想创建的果园(苹果,梨,香蕉):");            String s = "";            Scanner input = new Scanner(System.in);            s = input.nextLine();            if (s.equals("苹果")) {                new apple();            } else if (s.equals("香蕉")) {                new Banana();            } else if (s.equals("梨")) {                new Pear();            } else {                System.out.println("请输入正确的对象");            }        }}package study;public class Test {    public static void main(String[] args) {        // TODO Auto-generated method stub         new Garder().creater();                        }    }