[Java] Can you invoke an instance method or reference an instance variable from a static method? Can you invoke a static method or reference a static variable from an instance method? What is wrong in the following code?

1 public class C {
2     public static void main(String[] args) {
3         method1();
4     }
5
6     public void method1() {
7         method2();
8     }
9
10     public static void method2() {
11         System.out.println("What is radius " + c.getRadius());
12     }
13
14     Circle c = new Circle();
15 }

You can't invoke an instance method or instance variables from a static method since non static method/variables cannot be referenced from a static context.. You can invoke a static method or reference a static variable from an instance method? c is an instance variable, which cannot be accessed from the static context in method2. 


For an example:

However, you can invoke a static method or reference a static variable from an instance method Because static can be used without any instance of the class.

About what is wrong in provided code, at line 3, cannot invoke non-static method method1() without create an instance of classC and at line 11,method getRadius() haven't been defined, method getRadius() can't find.

Remarks
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Reference:
1) Introduction to Java Programming, Y. Daniel Liang 9.19
2) http://stackoverflow.com/questions/21397108/why-cant-a-static-method-refer-to-an-instance-method