java构造方法

1原始代码

class Point {
    double x, y;
    public Point(double _x, double _y) {
        x = _x;
        y = _y;  
    }
    public double getDistance(Point p) {
        return Math.sqrt((x - p.x) * (x - p.x) + (y - p.y) * (y - p.y));
    }
}
public class TestConstructor {
    public static void main(String[] args) {
        Point p = new Point(3.0, 4.0);
        Point origin = new Point(0.0, 0.0);
        System.out.println(p.getDistance(origin));
    }
}

2逐步分析

class Point {
    double x, y;
    public Point(double _x, double _y) {
        x = _x;
        y = _y;  
        System.out.println(x);
        System.out.println(y);
        System.out.println();

        
    }
    public double getDistance(Point p) {
        //它是穿了一个对象进来
    	//Point p, 是 origin的对象实例的地址
    	//上面那个Point p 实例里面是 x=0.1， y=0.2
    	//所以，那个p.x,表示0.1
        System.out.println(p.x);
        System.out.println(p.y);

        /*        System.out.println();
        System.out.println();
        System.out.println(p.x);
        System.out.println();
        System.out.println(y);
        System.out.println();
        System.out.println(p.y);
        System.out.println();
*/      
        return Math.sqrt((x - p.x) * (x - p.x) + (y - p.y) * (y - p.y));
    //    return "";
    }
}
public class TestConstructor {
    public static void main(String[] args) {
        Point p = new Point(3.0, 4.0);
        Point origin = new Point(0.1, 0.2);
        
//        System.out.println(p);
        
//        System.out.println();
        
//        System.out.println(origin);

//        System.out.println();

        System.out.println(p.getDistance(origin));
    }
}

3逐条注解

class Point{//定义一个Point类
    double x,y,z;//这个类有三个属性，x,y，z
    public Point(double _x,double _y,double _z){//构造函数给x,y,z赋初值
        x=_x;
        y=_y;
        z=_z;
    }
    public double getDistance(Point p){//一个public类型的成员函数计算Point p与开始赋值的点的（欧式）距离
        return Math.sqrt((x-p.x)*(x-p.x)+(y-p.y)*(y-p.y)+(z-p.z)*(z-p.z));
    }
}
 
class Test{
    public static void main(String[] args){
        Point p=new Point(3.0,4.0,5.0);//建了一个坐标为(3.0,4.0,5.0)的点，记为p
        Point origin=new Point(0.0,0.0,0.0);//建了一个坐标为(0.0,0.0,0.0)的点，记为origin
        System.out.println(p.getDistance(origin));//计算p与origin两点间的距离并打印到控制台
         
    }
}

//-----------------------

 

 Point.java

public class Point {
	private double x;
	private double y;
	private double z;
	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 double getZ() {
		return z;
	}
	public void setZ(double z) {
		this.z = z;
	}
	public Point(double x, double y, double z) {
		super();
		this.x = x;
		this.y = y;
		this.z = z;
	}
	/**
	 * 计算两个点的距离
	 * @param p
	 * @return
	 */
	public double distance(Point p){
		return Math.sqrt((x-p.x)*(x-p.x)+(y-p.y)*(y-p.y)+(z-p.z)*(z-p.z));
	}
	public static void main(String[] args) {
		Point p1 = new Point(1, 1, 1);
		Point p2 = new Point(2, 2, 2);
		System.out.println(p1.distance(p2));
	}
}