Skip to main content

Q) Create and make use of a user defined package?




A)
->if syntax is correct, only then package is created.
->”-d” destination of ‘.class’ file is not in the current working directory but in the user defined package.

//E:\today\imp\a.java
Package mypack;
Public class a
{
  Void x()
     {
         System.out.println(‘x method”);
     }
}
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
//E:\today\imp\b.java
Package mypack;
Public class b
{
    public void y()
     {
         a A= new a();
         A.x();
        Syste.out.prinln(“y method”);
     }
}
Note:
package statement should be the first non comment statement in the compilation unit.
E:\today\imp>javac –d . * .java
->’imp’ directory, “mypack” package is created a.class and b.class files are grouped (stored) in mypack.
->before we use “mypack” set the classpath. Place the fallowing value in classpath environment variable.
E:\todat\imp (using ‘;’ separator) (never include user defined here)

->java application that uses the user defined package?
//E:\c.java
Import mypack .b;
Class c
{
    Public static void main(String args[])
      {
            b B=new b();
            B.y();
      }
}
Here ‘public’ keyword is used in A.java and b.java before class and before method because ‘imp’ is separate directory and ‘mypack’ is separate so to a access the classes and method outside the ‘imp’ directory we uses access specified.

Public:
package mypack;
Import java.util.*;
Public class b
{
    Public void y()
     {
         A A=nre a();
         a.x();
         Scanner s=new Scanner(System.in);
     }
}

->now we meet to include ‘Scanner’ class using util package use import statement but ‘import’ should be written after the package statement only.
->if import mypack.*; is given in the code ‘*’ – works only when from imp directory we have to remove ‘.java’ files only  ‘.class’ files should be there or else import separately.
->suppose if we are working for www.yourdomain.com then if it is having user, admin modules then you are creating package for user then package com. yourdomain.user(reverse domain naming conversation).

Comments

Post a Comment

Popular posts from this blog

Q) What is JDBC driver? What is its role in java database connection?

A) ->A translation software written in java according o JDBC specification is nothing but “JDBC driver”. -> JDBC driver implements JDBC API. Use single API. JDBC driver role: They are 4 roles   1)       Establishing connection between JDBC client and database server. 2)       Receiving JDBC method calls made by JDBC client while performing database (CRUD) operations. 3)       Translating java method calls into DBMS understandable calls and forwarding them to database server. 4)       Receiving the results from database server. Translating them into java format and handling over the same to the JDBC client.
Post a Comment
Read more

Q) What is ODBC?

A) ->open database connectivity is a technology from MS that enables any language program (other than java) to communication with database Management System. ->in java program ODBC is directly not allowed for the fallowing reasons 1) OS dependency 2) Procedural oriented approach 3) Security thread
Post a Comment
Read more

Q) Explain about nested classes?

A) ->defining a class with in another class is known as nesting of the class. Ex: class A {        class B        {                      } //nested class, and inner class.because it is not static class. } //enclosing class or outer class. ->static class is declared in inside an another class then it does not become an inner class. Note: non-static nested class is known as “inner class”. In the above example class B is nested but not an inner class. Ex: class D {        static c        {                      } //nested class, but not an inner class , because of static class. } //outer class. ->we have three different kinds of inner classes. 1) Member inner class 2) Meth...
Post a Comment
Read more