java学习——构造类

package my_project;

public class my_first_class {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Point p1 = new Point();
        p1.setX(8.0);
        p1.setY(9.0);
        Circle c1 = new Circle();
        c1.setCentre(p1);
        c1.setRadius(1.0);//设置c1的半径
        
        System.out.println("圆心(x,y)= " + "(" + c1.getCentre().getX() + "," +
                + c1.getCentre().getY() + ")");
        System.out.println("圆的半径 = " + c1.getRadius());
        System.out.println("圆的面积= " + c1.getArea());
        System.out.println("圆的周长= " + c1.getCircleLong());

    }

}
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 double setY(double y)
    {
        return this.y=y;
    }
}

class Circle{
    
    private Point centre;
    
    private double radius;
    
    final static double PI = 3.1415926;//PI常量(最终类变量)
    
    public Point getCentre()
    {
        return centre;
    }
    
    public void setCentre(Point centre)
    {
        this.centre = centre;
    }
    
    public double getRadius()
    {
        return radius;
    }
    
    public void setRadius(double radius)
    {
        this.radius=radius;
    }
    
    public double getArea()
    {
        return PI*Math.pow(radius,2);
    }
    
    public double getCircleLong()
    {
        return 2*PI*radius;
    }
}

package hello;

public class Student {
    
    String xm,xh,xb;
    
    Student(){
    }
    
    public Student(String xm, String xh, String xb){
        this.xm=xm;
        this.xh=xh;
        this.xb=xb;
    }
    
    public String getXm() {
        return xm;
    }

    public void setXm(String xm) {
        this.xm = xm;
    }

    public String getXh() {
        return xh;
    }

    public void setXh(String xh) {
        this.xh = xh;
    }

    public String getXb() {
        return xb;
    }

    public void setXb(String xb) {
        this.xb = xb;
    }


    public String toString() {
        return "Student [xm=" + xm + ", xh=" + xh + ", xb=" + xb + "]";
    }
    
    public void Print() {
        System.out.println("Student [xm=" + xm + ", xh=" + xh + ", xb=" + xb + "]");
    }

}