第二次java上机参考

java作业

万物皆有始终，本例程可以经过小许改变解燃眉之急，但是切不可依赖。要知耻而后勇。---------------曾经的我也尝过很急但是不会的滋味！！！共勉！！！题很简单，可是你不会呀！一定要端正态度！

2

创建一个NewRetangl类，该类有两个不同的构造方法，分别实现拿到面积和周长的方法

package javaAssignment.second;
public class NewRectangle {
    private double width;
    private double height;
    public NewRectangle() {
        width = 0;
        height = 0;
    }
    public NewRectangle(double w, double h) {
        width = w;
        height = h;
    }
    private double getArea() {
        return height * width;
    }
    private double getPerimeter() {
        return 2 * (height + width);
    }
    public static void main(String[] args) {
        NewRectangle nr = new NewRectangle(10.2, 2.5);
        NewRectangle nr1 = new NewRectangle();
        System.out.println(nr.getArea());
        System.out.println(nr.getPerimeter());
        System.out.println(nr1.getArea());
        System.out.println(nr1.getPerimeter());
    }
}

运行结果：

25.5
25.4
0.0
0.0

3

（1）

新建point类

class Point {
    private double x;
    private double y;
    public Point() {
        x = 0.0;
        y = 0.0;
    }
    public Point(double x, double y) {
        this.x = x;
        this.y = y;
    }
    private double distance(Point p) {
        double dx = x - p.x;
        double dy = y - p.y;
        return Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
    }
}

(2)（3）（4）

关于点是否在矩形中，利用左下角的点进行平移

package javaAssignment.second;
class Point {
    private double x;
    private double y;
    public double getX() {
        return x;
    }
    public void setX(double x) {
        this.x = x;
    }
    public double getY() {
        return y;
    }
    public void setY(double y) {
        this.y = y;
    }
    public Point() {
        x = 0.0;
        y = 0.0;
    }
    public Point(double x, double y) {
        this.x = x;
        this.y = y;
    }
    private double distance(Point p) {
        double dx = x - p.x;
        double dy = y - p.y;
        return Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
    }
}
public class NewRectangle {
    private double width;
    private double height;
    private Point p;
    public NewRectangle() {
        width = 0;
        height = 0;
    }
    public NewRectangle(double w, double h, double x, double y) {
        p = new Point();
        width = w;
        height = h;
        p.setX(x);
        p.setY(y);
    }
    private double getArea() {
        return height * width;
    }
    private double getPerimeter() {
        return 2 * (height + width);
    }
    private boolean bPointIn(Point p1) {
        double Dx = p1.getX() - p.getX();
        double Dy = p1.getY() - p.getY();
        if ((Dx <= 0 && Dx >= -width) && (Dy >= 0 && Dy <= height)) {
            return true;
        }
        return false;
    }
    public static void main(String[] args) {
        NewRectangle nr = new NewRectangle(10, 10, 0, 1);
        NewRectangle nr1 = new NewRectangle();
        System.out.println(nr.getArea());
        System.out.println(nr.getPerimeter());
        Point p1 = new Point(-1, 0);
        System.out.println(nr.bPointIn(p1));
    }
}

测试数据输出：

100.0
40.0
false

9

（1）

package javaAssignment.second;
class Cycle {
    public void ride(Cycle c) {
        System.out.println(c);
    }
}
class Unicycle extends Cycle {
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "Unicycle";
    }
}
class Bicycle extends Cycle {
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "Bicycle";
    }
}
class Tricycle extends Cycle {
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "Tricycle";
    }
}
public class NO_9 {
    public static void main(String[] args) {
        Cycle c = new Cycle();
        Unicycle uc = new Unicycle();
        Bicycle bc = new Bicycle();
        Tricycle tc = new Tricycle();
        c.ride(uc);
        c.ride(bc);
        c.ride(tc);
    }
}

测试结果：

Unicycle
Bicycle
Tricycle

（2）

package javaAssignment.second;
class Cycle {
    public void ride(Cycle c) {
        System.out.println(c + " " + c.wheel());
    }
    public int wheel() {
        return 0;
    }
}
class Unicycle extends Cycle {
    private int wheels = 1;
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "Unicycle";
    }
    @Override
    public int wheel() {
        // TODO Auto-generated method stub
        return wheels;
    }
}
class Bicycle extends Cycle {
    private int wheels = 2;
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "Bicycle";
    }
    @Override
    public int wheel() {
        // TODO Auto-generated method stub
        return wheels;
    }
}
class Tricycle extends Cycle {
    private int wheels = 3;
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "Tricycle";
    }
    @Override
    public int wheel() {
        // TODO Auto-generated method stub
        return wheels;
    }
}
public class NO_9 {
    public static void main(String[] args) {
        Cycle c = new Cycle();
        Unicycle uc = new Unicycle();
        Bicycle bc = new Bicycle();
        Tricycle tc = new Tricycle();
        c.ride(uc);
        c.ride(bc);
        c.ride(tc);
    }
}

(3)

在ride（）方法中使用一个instanceof

package javaAssignment.second;
class Cycle {
    public void ride(Cycle c) {
        if (c instanceof Unicycle) {
            ((Unicycle) c).balance();
        } else if (c instanceof Bicycle) {
            ((Bicycle) c).balance();
        } else {
            System.out.println("This is a instance of Tricycle");
        }
    }
    public int wheel() {
        return 0;
    }
}
class Unicycle extends Cycle {
    private int wheels = 1;
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "Unicycle";
    }
    @Override
    public int wheel() {
        // TODO Auto-generated method stub
        return wheels;
    }
    public void balance() {
        System.out.println("Unicycle balance");
    }
}
class Bicycle extends Cycle {
    private int wheels = 2;
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "Bicycle";
    }
    @Override
    public int wheel() {
        // TODO Auto-generated method stub
        return wheels;
    }
    public void balance() {
        System.out.println("Bicycle balance");
    }
}
class Tricycle extends Cycle {
    private int wheels = 3;
    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "Tricycle";
    }
    @Override
    public int wheel() {
        // TODO Auto-generated method stub
        return wheels;
    }
}
public class NO_9 {
    public static void main(String[] args) {
        Cycle c = new Cycle();
        Cycle uniCycle = new Unicycle();
        c.ride(uniCycle);
    }
}

结果：

Unicycle balance