What is a “runtime class” in Java?

Question

I try to understand what the Object.getClass() method does.

The documentation says that it \"returns the runtime class of an object.\" That explanation

Answer 1

It means "the class of the instance the variable refers to at runtime" (sorry if that's not actually clearer).

If you have a reference to an Object, it could refer to an Object, a String, an Integer... you get that class, not Object.

Object obj1 = new Object();
System.out.println(obj1.getClass());  // java.lang.Object

String obj2 = "";
System.out.println(obj2.getClass());  // java.lang.String

obj1 = obj2;
System.out.println(obj1.getClass());  // java.lang.String, not Object.