第一题

import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.geom.PathIterator;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.Scanner;//把main 函数的给替换了
public static void main(String[] args) {Scanner scanner = new Scanner(System.in);double radius = scanner.nextDouble();double length = scanner.nextDouble();double width = scanner.nextDouble();Circle circle = new Circle(radius);Rectangle rectangle = new Rectangle(length, width);System.out.println(circle.getAcreage());System.out.print(rectangle.getAcreage());}abstract class shape{public abstract void getAcreage();
}class Circle implements Shape {private double radius;public Circle() {}public Circle(double radius) {this.radius = radius;}public double getRadius() {return radius;}public void setRadius(double radius) {this.radius = radius;}@Overridepublic java.awt.Rectangle getBounds() {return null;}@Overridepublic Rectangle2D getBounds2D() {return null;}@Overridepublic boolean contains(double x, double y) {return false;}@Overridepublic boolean contains(Point2D p) {return false;}@Overridepublic boolean intersects(double x, double y, double w, double h) {return false;}@Overridepublic boolean intersects(Rectangle2D r) {return false;}@Overridepublic boolean contains(double x, double y, double w, double h) {return false;}@Overridepublic boolean contains(Rectangle2D r) {return false;}@Overridepublic PathIterator getPathIterator(AffineTransform at) {return null;}@Overridepublic PathIterator getPathIterator(AffineTransform at, double flatness) {return null;}public double getAcreage() {return 3.1415926 * getRadius() * getRadius();}
}class Rectangle implements Shape {private double length;private double width;public double getLength() {return length;}public void setLength(double length) {this.length = length;}public double getWidth() {return width;}public void setWidth(double width) {this.width = width;}public Rectangle() {}public Rectangle(double length, double width) {this.length = length;this.width = width;}@Overridepublic java.awt.Rectangle getBounds() {return null;}@Overridepublic Rectangle2D getBounds2D() {return null;}@Overridepublic boolean contains(double x, double y) {return false;}@Overridepublic boolean contains(Point2D p) {return false;}@Overridepublic boolean intersects(double x, double y, double w, double h) {return false;}@Overridepublic boolean intersects(Rectangle2D r) {return false;}@Overridepublic boolean contains(double x, double y, double w, double h) {return false;}@Overridepublic boolean contains(Rectangle2D r) {return false;}@Overridepublic PathIterator getPathIterator(AffineTransform at) {return null;}@Overridepublic PathIterator getPathIterator(AffineTransform at, double flatness) {return null;}public double getAcreage() {return getLength()*getWidth();}
}

第二题

    public static void main(String[] args) {Scanner scanner = new Scanner(System.in);String name = scanner.next();String birth = scanner.next();String position = scanner.next();double salary = scanner.nextDouble();Salary employee = new Salary(name, birth, position, salary);employee.introduction();}/********** Begin *********/
class Employee {private String name;private String birth;private String position;public Employee() {}public Employee(String name, String birth, String position) {this.name = name;this.birth = birth;this.position = position;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getBirth() {return birth;}public void setBirth(String birth) {this.birth = birth;}public String getPosition() {return position;}public void setPosition(String position) {this.position = position;}
}class Salary extends Employee {private double salary;public double getSalary() {return salary;}public void setSalary(double salary) {this.salary = salary;}public Salary(String name, String birth, String position, double salary) {super(name, birth, position);this.salary = salary;}public void introduction(){System.out.println("员工姓名："+getName()+" 出生年月："+getBirth()+" 职位："+getPosition()+" 薪水："+getSalary());}
}
/********** End *********/

第三题

    public static void main(String[] args) {/********** Begin *********/Animal cat = new Cat();Animal dog = new Dog();/********** End *********/cat.eat();cat.work();dog.eat();dog.work();}abstract class Animal {abstract void eat();abstract void work();
}/********** Begin *********/
class Cat extends Animal {@Overridepublic void eat(){System.out.println("吃鱼");}@Overridepublic void work(){System.out.println("抓老鼠");}}class Dog extends Animal {@Overridepublic void eat(){System.out.println("吃骨头");}@Overridepublic void work(){System.out.println("看家");}}