？java——无法从静态上下文中引用非静态变量

/**
 * Created by xabcd on 2019/2/16.
 */
public class total_jiekou
{
    interface A
    {
        int i = 10;
        public void sayI();
    }
    interface E
    {
        int x = 40;
        public void sayE();
    }
    interface B extends A,E{
        int j = 20;
        public void sayJ();
    }
    class C implements B {
        public void sayI()

        {
            System.out.println("i=" + i);
        }

        public void sayJ()

        {
            System.out.println("j=" + j);
        }

        public void sayE()

        {
            System.out.println("e=" + x);
        }
    }
    public static void main(String[] args)
    {
        C c = new C();//红色异常
        c.sayI();
        c.sayJ();
    }

}