Java出现No enclosing instance of type E is accessible. Must qualify the allocation with an enclosing

阳光穿透心脏的1/2处 2022-05-12 04:54 166阅读 0赞

最近在看Java，在编译写书上一个例子时，由于书上的代码只有一部分，于是就自己补了一个内部类。结果编译时出现：No enclosing instance of type E is accessible. Must qualify the allocation with an enclosing instance of type E(e.g. x.new A() where x is an instance of E). E指代我写的那个内部类。

根据提示**，没有可访问的内部类E的实例，必须分配一个合适的内部类E的实例（如x.new A()，x必须是E的实例。）**看着这句提示，我就纳闷了，我已经用new实例化了这个类，为什么还不行呢。

于是百度谷歌了一下相关资料。原来我写的内部类是动态的，也就是开头以public class开头。而主程序是public static class main。在Java中，类中的静态方法不能直接调用动态方法。只有将某个内部类修饰为静态类，然后才能够在静态类中调用该类的成员变量与成员方法。所以**在不做其他变动的情况下，最简单的解决办法是将新写的类的public class改为public static class.**

package jave;
    
    public class Point {
    	private double x;
    	private double y;
    	Point(double x1, double y1){
    		x = x1;
    		y = y1;
    	}
    	public double getX() {
    		return x;
    	}
    	public double getY() {
    		return y;
    	}
    	public void setX(double i) {
    		x = i;
    	}
    	public void setY(double i) {
    		y = i;
    	}
    	
    	
    public static class Circle{
    		private Point o;//圆心
    		private double radius;//半径
    		//构造函数
    		Circle(Point p, double r) {
    			o = p;
    			radius = r;
    		}
    		//构造函数的重载
    		Circle(double r) {
    			o = new Point(0.0, 0.0);//初始化圆心在原点
    			radius = r;
    		}
    		//判断该点在不在圆里
    		boolean contains(Point p) {
    			double x = p.getX() - o.getX();
    			double y = p.getY() - o.getY();
    			if((x*x + y*y) > radius*radius)
    				return false;
    			else 
    				return true;
    		}
    		public void setO(double x, double y) {
    			o.setX(x);
    			o.setY(y);
    		}
    		public Point getO() {
    			return o;
    		}
    		public double getRadius() {
    			return radius;
    		}
    		public void setRadius(double r) {
    			radius = r;
    		}
    		public double area() {
    			return 3.14 * radius *radius;
    		}
    	}
    	
    	
    	
    	public static void main(String[] args) {
    		Circle c1 = new Circle(new Point(1.0, 2.0), 2.0);
    		Circle c2 = new Circle(5.0);
    		System.out.println("c1:(" + c1.getO().getX() + "," + c1.getO().getY() + ")," + c1.getRadius());
    		System.out.println("c2:(" + c2.getO().getX() + "," + c2.getO().getY() + ")," + c2.getRadius());
    		System.out.println("c1 area = " + c1.area());
    		System.out.println("c2 area = " + c2.area());
    		c1.setO(5, 6);
    		c2.setRadius(9.0);
    		System.out.println("c1:(" + c1.getO().getX() + "," + c1.getO().getY() + ")," + c1.getRadius());
    		System.out.println("c2:(" + c2.getO().getX() + "," + c2.getO().getY() + ")," + c2.getRadius());
    		System.out.println("c1 area = " + c1.area());
    		System.out.println("c2 area = " + c2.area());
    		
    		
    		Point p1 = new Point(5.2, 6.3);
    		System.out.println(c1.contains(p1));
    		System.out.println(c1.contains(new Point(10.9, 9.0)));
    
    	}
    
    }

即将public class Circle 改为public static class Circle， public void main(String\[\] args)改为public static void main(String\[\] args)。