package Test;
class Point{
double x;
double y;
public Point(double _x,double _y){
x = _x;
y = _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;
}
}
class Circle{
private Point o;
private double r;
public Circle(Point p,double r){
p = p;
r = r;
}
public Point getP()
{
return o;
}
public void setP(Point p)
{
this.o = p;
}
public double getR()
{
return r;
}
public void setR(double r)
{
this.r = r;
}
boolean disance(Point p){//包不包含一个点就传一个点对象进来
double x = p.getX()-o.getX();
double y = p.getY()-o.getY();
if(x * x + y * y > r * r){
return false;
}
else return true;
}
}
public class Test {
public static void main(String[] args)
{
Circle c = new Circle(new Point(10, 10), 5);
Point p1 = new Point(11, 11);
System.out.println(c.disance(p1));
}
}
这个程序主要实现测试一个点是不是包含在一个园内，程序经运行提示空指针，自己仔细分析就是找不出为什么，请高手指明，谢谢
------解决方案--------------------
Circle的构造方法有问题，导致o和r 没有设置成功，改成下面的就OK了
- Java code
class Point{ double x; double y; public Point(double _x,double _y){ x = _x; y = _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; }}class Circle{ private Point o; private double r; public Circle(Point p,double r){ this.o = p; //这里进行修改 this.r = r; //这里进行修改 } public Point getP() { return o; } public void setP(Point p) { this.o = p; } public double getR() { return r; } public void setR(double r) { this.r = r; } boolean disance(Point p){//包不包含一个点就传一个点对象进来 double x = p.getX()-o.getX(); double y = p.getY()-o.getY(); if(x * x + y * y > r * r){ return false; } else return true; }}public class Test { public static void main(String[] args) { Circle c = new Circle(new Point(10, 10), 5); Point p1 = new Point(11, 11); System.out.println(c.disance(p1)); }}
------解决方案--------------------
- Java code
class Point { double x; double y; public Point(double _x, double _y) { x = _x; y = _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; }}class Circle { private Point o; private double r; public Circle(Point p, double r) { // error // p = p; this.o = p; this.r = r; } public Point getP() { return o; } public void setP(Point p) { this.o = p; } public double getR() { return r; } public void setR(double r) { this.r = r; } boolean disance(Point p) {// 包不包含一个点就传一个点对象进来 double x = p.getX() - o.getX(); double y = p.getY() - o.getY(); if (x * x + y * y > r * r) { return false; } else return true; }}public class Main { public static void main(String[] args) { Circle c = new Circle(new Point(10, 10), 5); Point p1 = new Point(11, 11); System.out.println(c.disance(p1)); }}