梁勇——Java语言程序设计第十三章编程练习题（部分）

13.1

GeometricObject类

public abstract class GeometricObject{
    private String color = "white";
    private boolean filled;  //是否要上色
    private java.util.Date dateCreated;

    public GeometricObject() {
        dateCreated = new java.util.Date();
    }

    public GeometricObject(String color, boolean filled) {
        dateCreated = new java.util.Date();
        this.color = color;
        this.filled = filled;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public boolean getFilled() {
        return filled;
    }

    public void setFilled(boolean filled) {
        this.filled = filled;
    }

    public boolean isFilled(){
        return filled;
    }

    public java.util.Date getDateCreated() {
        return dateCreated;
    }

    @Override
    public String toString() {
        return "created on " + dateCreated + "\ncolor: " + color + " and filled: " + filled;
    }

    //抽象方法
    public abstract double getArea();
    public abstract double getPerimeter();
}

Triangle类

public class Triangle extends GeometricObject implements Comparable<Triangle>{
    private double side1 = 1.0;
    private double side2 = 1.0;
    private double side3 = 1.0;

    public Triangle() {

    }

    public Triangle(double side1, double side2, double side3,
                    String color, boolean filled) {
        this.side1=side1;
        this.side2=side2;
        this.side3=side3;
        setColor(color);
        setFilled(filled);
    }


    public double getSide1() {
        return side1;
    }

    public double getSide2() {
        return side2;
    }

    public double getSide3() {
        return side3;
    }


    @Override
    public  double getArea() {
        double p = (side1 + side2 + side3) / 2;
        double temp = p * (p - side1) * (p - side2) * (p - side3);
        return Math.sqrt(temp);
    }

    @Override
    public double getPerimeter() {
        return side1+side2+side3;
    }

    @Override  
    public int compareTo(Triangle o) {
        if(getArea()>o.getArea())
            return 1;
        else if(getArea()<o.getArea())
            return -1;
        else
            return 0;
    }

    @Override
    public String toString(){
        return "side1: " + side1 + " side2: " + side2 + " side3: " + side3 +" Area: " +getArea();
    }

    //调用父类的toString
    public String superToString(){
        return super.toString();
    }


    public static double maxPerimeter(GeometricObject ob1,GeometricObject ob2){
        if (ob1.getPerimeter()>ob2.getPerimeter())
            return ob1.getPerimeter();
        else if(ob1.getPerimeter()<ob2.getPerimeter())
            return ob2.getPerimeter();
        else
            return 0;
    }
}

测试类

public class TriangleTest {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter there side:");
        double side1 = input.nextDouble();
        double side2 = input.nextDouble();
        double side3 = input.nextDouble();
        System.out.print("setColor：");
        String color=input.next();
        System.out.print("filled?(true/false)：");
        boolean filled=input.nextBoolean();
        input.close();

        Triangle object1 =new Triangle(side1,side2,side3,color,filled);

        System.out.println("Area："+object1.getArea());
        System.out.println("Perimeter："+object1.getPerimeter());
        System.out.println(object1.superToString());

    }
}

测试类2（非书本要求）

public class TriangleTest2 {
    public static void main(String[] args) {
       Triangle ob1 = new Triangle(3,4,5,"white",true);
       Triangle ob2 = new Triangle(6,8,10,"white",true);
        System.out.println("MAX_Perimeter: "+Triangle.maxPerimeter(ob1,ob2));
        System.out.println("ob1_Area>ob2_Area ? 1:-1 \nreturn:" + ob1.compareTo(ob2));
        System.out.println("________________________________________________________");
        Triangle obs[] = {
                new Triangle(3,4,5,"white",true),
                new Triangle(6,8,10,"white",true),
                new Triangle(5,11,12,"white",true),
        };
        java.util.Arrays.sort(obs);
        for(Triangle ob:obs){
          System.out.print(ob.toString() + " ");
            System.out.println();
        }
    }
}

13.7

Conlor接口

public interface Colorable {
    public abstract void howToColor();
}

Square类

public class Square extends GeometricObject implements Colorable{
    private double side;

    public Square(){
        this.side =0;
    }

    public Square(double side,String color,boolean filled){
        this.side = side;
        setColor(color);//调用父类已有方法
        setFilled(filled);//调用父类已有方法
    }

    public double getSide() {
        return side;
    }

    public void setSide(double side) {
        this.side = side;
    }

    @Override
    public void howToColor() {
        System.out.println("Color all four sides");
    }

    @Override
    public double getArea() {
        return Math.pow(side,2);
    }

    @Override
    public double getPerimeter() {
        return side*4;
    }
}

测试类

public class SquareTest {
    public static void main(String[] args) {
        GeometricObject[] obs = {new Square(1,"white",true),new Square(2,"yellow",true)};
        Square t = null;
        for(GeometricObject ob:obs){
            if(ob instanceof Square)
                t = (Square)ob;
            if(t.isFilled())
                t.howToColor();
        }
    }
}