Question

Does this code get called for every object creation in Java, because every object extends Object ? Or does the JVM optimize it in some way to avoid the creation of some many Object’s object in the heap.

What exactly happens in this method registerNatives().

package java.lang;  

public class Object {
  private static native void registerNatives();
  static {
    registerNatives();
  }

Answer 1

Static blocks are only executed once, when the class is loaded.

As explained here or here, a block that will be executed every time an object of the class is initialized can also be defined : just remove the static keyword.