Java tid bits :

1 : A class that implpementing an interface becomes an abstract class if it dont implements all the functions declared inside Interface and hence cant be used for instantiating objects

2 : Interfaces having only variables can be used for making set of Global Constants which can be used by other classes , just like constants declared in C header files


3 : Packages help in resuing classes across programmes
4 : Only at runtime, interpreter loads the class used from other package , during compilation , compiler only  checks whther the .class file is present in package imported

5: A java source file can only have one class declared as public because filename should be same as the public class with .java extension . But many non public classes can be defined

6:
Exception class is a subclass of Throwable , hence so do all user defined exceptions

7 : in switch case statements only constant values or literals are allowed
 final String a = "" , b = "fa";
     switch("dgh")
     {
     case "sdg":
         break;
     case a+b :
         break;
     }
    
8:  Runtime : polymorphism (overriding) and Compiletime - Inheritance of methods and attributes by subclasses

9 :  Java's interpreter do thread switching for multi threading
10 : States of a Thread :
New Born State : When an object of a class extending java.lang.Thread is made
Runnable state : on calling start()
Running state : Java runtime schedules thread calling run()