Question

我一步一步地跟着我们在课堂上如何做到这一点，但是当我尝试编译时，我得到了以下错误：

错误：非静态变量，无法从静态上下文中引用。

受质疑的是 cir1 = new Circle（）; 和 cir2 = new Circle（）;

我理解错误意味着我只是很难看到我的错误，因为它与我们在课堂上所做的完全相同（或者我认为......）

 public class CircleDemo{
   public static void main(String[] args){
      Circle cir1, cir2;
      cir1 = new Circle();
      cir2 = new Circle();
      cir1.setRadius(3.0);
      cir2.setRadius(11.01);
      System.out.println("Area of the first circle: " + cir1.findArea());
       System.out.println("Circumference of the first circle: " + cir1.findCircumference());
       System.out.println("Area of the second circle: " + cir2.findArea());
       System.out.println("Circumference of the second circle: " +         cir2.findCircumference());
}

 public class Circle{
 //Instance Variables
 private double PI = 3.1459;
 private double radius;
 //Methods
 public Circle ( ) { }

 //get method (Accessor Methods )
 public double getRadius ( ) {
 return radius;
  }
 //set method (Mutator Methods)
 public void setRadius (double r) {
 radius=r;
 }
 public double findArea ( ) {
 return PI*radius*radius; //area= pi r squared
 }
 public double findCircumference ( ) {
 return 2 * PI * radius;
}
}//end Circle
}

如果有人能帮助我理解我做错了什么，我将不胜感激！谢谢。

Answer 1

这似乎是一个简单的括号错误。也许是滥用关键字＆＃34; public＆＃34;在Circle类定义中。以下是修订后的代码：

public class CircleDemo {
    public static void main(String[] args){
        Circle cir1, cir2;
        cir1 = new Circle();
        cir2 = new Circle();
        cir1.setRadius(3.0);
        cir2.setRadius(11.01);
        System.out.println("Area of the first circle: " + cir1.findArea());
        System.out.println("Circumference of the first circle: " + cir1.findCircumference());
        System.out.println("Area of the second circle: " + cir2.findArea());
        System.out.println("Circumference of the second circle: " +         cir2.findCircumference());

    } //Added this bracket
}

class Circle { //removed the word "public" I'll this explain below
    //Instance Variables
    private double PI = 3.1459;
    private double radius;
    //Methods
    public Circle () {}

    //get method (Accessor Methods )
    public double getRadius ( ) {
        return radius;
    }
    //set method (Mutator Methods)
    public void setRadius (double r) {
        radius=r;
    }
    public double findArea ( ) {
        return PI*radius*radius; //area= pi r squared
    }
        public double findCircumference ( ) {
        return 2 * PI * radius;
    }
} //Removed an extra bracket here

一些不正确的括号导致错误。此外，如果Circle类与CircleDemo类在同一文件中定义，则Circle类必须不定义为＆＃34; public＆＃34;，因为这会导致错误。如果Circle类在其自己的文件中定义，那么它可以是＆＃34; public＆＃34;。我对此进行了测试以确保其正常工作。

圆类定义使用静态错误进行编译

1 个答案: