Example of an instance method? (Java)

class InstanceMethod
    {
     public static void main(String [] args){
         InstanceMethod obj = new InstanceMethod();// because that method we wrote is instance we will write an object to call it
           System.out.println(obj.sum(3,2));
     }
     int f;
     public double sum(int x,int y){// this method is instance method because we dont write static

          f = x+y;
          return f;
      }
  }

If it's not a static method then it's an instance method. It's either one or the other. So yes, your method,

public void example(String random) {
  // this doesn't appear to do anything
}

is an example of an instance method.

Regarding

and was wondering how exactly you might use an instance method

You would create an instance of the class, an object, and then call the instance method on the instance. i.e.,

public class Foo {
   public void bar() {
      System.out.println("I'm an instance method");
   }
}

which could be used like:

Foo foo = new Foo(); // create an instance
foo.bar(); // call method on it

*An instance method * is a method is associated with objects, each instance method is called with a hidden argument that refers to the current object. for example on an instance method :

public void myMethod  {
      // to do when call code
}