编译报错:ClassMemberDemo.java:22:找不到符号
变量:PI
位置:类Math return Math.PI*radius*radius;(唉,不知道是怎么回事)class Point
{
int x,y;
public Point(int x,int y)
{
this.x=x;
this.y=y;
}
}
class Circle
{
Point center= new Point(0,0);
double radius;
public Circle(int x,int y,double r)
{
center.x=x;
center.y=y;
radius =r;
}
public double area()
{
return Math.PI*radius*radius;
}
}public class ClassMemberDemo
{
public static void main(String[] args)
{
Circle c1=new Circle(100,100,10);
System.out.println("Circle center point is:"+c1.center.x+","+c1.center.y);
System.out.println("Circle radius is:"+c1.radius);
System.out.println("Circle area is:"+ c1.area());
}
}
变量:PI
位置:类Math return Math.PI*radius*radius;(唉,不知道是怎么回事)class Point
{
int x,y;
public Point(int x,int y)
{
this.x=x;
this.y=y;
}
}
class Circle
{
Point center= new Point(0,0);
double radius;
public Circle(int x,int y,double r)
{
center.x=x;
center.y=y;
radius =r;
}
public double area()
{
return Math.PI*radius*radius;
}
}public class ClassMemberDemo
{
public static void main(String[] args)
{
Circle c1=new Circle(100,100,10);
System.out.println("Circle center point is:"+c1.center.x+","+c1.center.y);
System.out.println("Circle radius is:"+c1.radius);
System.out.println("Circle area is:"+ c1.area());
}
}
结果
Circle center point is:100,100
Circle radius is:10.0
Circle area is:314.1592653589793
我的也没写 import java.lang.Math 也没报错啊。。
一般是运行时,java虚拟机通过设置的classpath找到lib下的包
你想让它自动找到,就加到classpath中就可以了你的classpath里面要加入 '.'