Static and Non-Static

Static variables and methods are shared across all the objects.
Static variables and methods can directly access through class name

1.Static methods can access only static stuff (directly).
2.static methods can also access non static stuff but through object.
3.Non static methods can access everything (static and non-static - direct access)

Example:

public class StaticAndNonStatic {
    //Global variables --the scope of global variables will be available across all the functions with some condition
     String Name="John";  //Non static global variable
       static int age=30;  //Static variable
    public static void main(String[] args) {
  
        //How to call static methods and variables
        //1.Direct calling
        add();
        System.out.println(age);
       
        //2.Calling by class name
        StaticAndNonStatic.add();
        System.out.println(StaticAndNonStatic.age);
       
       
        //How to call non static method and variables
        //By creating object
        StaticAndNonStatic obj=new StaticAndNonStatic();
        obj.sum();
        System.out.println(obj.Name);
       
       
        //Can i access static methods by using object reference?yes
        obj.add();//waring will be given
 
    }
   
    public void sum() { //non static method
        System.out.println("This is a non static method");
    }
   
    public static void add() { //Static method
        System.out.println("This is a static method");
    }

}

What is 'System.out.println()' ?

For the class 'Test' we can write 'Test.s.lenth()'

class Test
{
   static String s="Welcome";
}

like for the class 'System' we can write 'System.out.println()'

class System
{
   static PrintStream out;
}