Basic Java Knowledge

1. Interfaces can only be modified with public

2 http: Hypertext Transfer Protocol Port 80

SMTP: Simple Mail Transfer Protocol port 25

FTP ssh 22

3 public int Amethod () {
static int i=0;
i++;
}

Compile error, cannot declare static variable in class

4 class Super {
Public Integer Getlenght () {return Newinteger (4);}
}

public class Sub extends Super {
Public long Getlenght () {return new Long (5);}
public static void Main (string[] args) {
Super Sooper = new super ();
Sub Sub = new sub ();
System.out.println (Sooper.getlenght (). toString () + "," +
Sub.getlenght (). toString ());
}
}

Compilation failed.---------Retiming cannot change the return type

5

classparent{String name= "Parent_name"; Static{System.out.println ("Parent_static"); }     PublicParent () {//TODO auto-generated Constructor stubSystem.out.println ("Parent_constructor"); }     Public voidmethod () {System.out.println ("Parent"); }     Public Static voidSmethod () {System.out.println ("Parent_1"); }}classChildextendsparent{String name= "Child_name"; Static{System.out.println ("Child_static"); }     PublicChild () {//TODO auto-generated Constructor stubSystem.out.println ("Child_constructor"); }     Public voidmethod () {System.out.println ("Child"); }     Public Static voidSmethod () {System.out.println ("Child_1"); }} Public classTEST5 { Public Static voidMain (string[] args) {child C=NewChild (); System.out.println ("---------------"); Parent P=NewParent (); System.out.println ("------------------");        P.method (); System.out.println ("--------------");        C.method (); System.out.println ("--------------"); Parent DDD=NewChild (); System.out.println ("--------------");        System.out.println (Ddd.name);    Ddd.method (); }}

Basic Java Knowledge