Packages in confusion

Question

Hello Experts/ Gurus
I am planning to finish  PL/SQL concept  very soon.  Now i am learning PL/SQL packages.
i dont understand clearly folkowing term.
Any subprogram not in the package specification but coded in the package body is called a private object.
         what i understood ,  package body having  logical code  for any one procedure  but  it's not mentioned in  "package specification"  area
         Can anyone provide  small example for  above comment ?
                I tried as much as possible , no code found like  above mentioned.
Thanks  in advance ..

Answer 1

@ FRANKLUSH
SCOTT>CREATE OR REPLACE PACKAGE  test_pk
  2  AS
  3  FUNCTION hello
  4  RETURN   VARCHAR2;
  5  END  test_pk;
  6  /
Package created.
SCOTT>CREATE OR REPLACE PACKAGE BODY  test_pk
  2  AS
  3  FUNCTION  who
  4  RETURN    VARCHAR2
  5  IS
  6  BEGIN
  7  RETURN  'World';
  8  END  who;
  9  FUNCTION  hello
10  RETURN    VARCHAR2
11  IS
12  BEGIN
13  RETURN  'Hello, ' || who
14  || '!';
15  END  hello;
16  END  test_pk;
17  /
Package body created.
SCOTT>sELECT test_pk.hello   AS test_pk_hello FROM dual;
TEST_PK_HELLO
Hello, World!
SCOTT>SELECT test_pk.who     AS test_pk_who from dual;
SELECT test_pk.who     AS test_pk_who from dual
* ERROR at line 1:
ORA-00904: "TEST_PK"."WHO": invalid identifier
Thanks !  This works well !