What is this?
public class ABC { public ABC() { System.out.println(\"world\"); } static { System.out.println(\"hello\"); } }
It's called a "static initialisation block".
It runs when the class is first loaded; only once.
For example, a constructor will run each time the class is instantiated; the static block only runs once, when it's first loaded statically by the VM/Class loader.