Can an Static Method call an Instance Method in Java

Static methods can always call instance methods - so long as they have a reference to an instance on which to call the method.

For example:

public static void main(String[] args) {
    String foo = "hello";
    System.out.println(foo.length());
}

length() is an instance method on String, main is a static method, but I'm still fine to call it... because foo provides a reference.

The only difference between static methods and instance methods in this regard is that an instance method implicitly has a reference to the type in which the method is declared - this.