Skip to main content

What is the mean of re-usability in Java ?

Object oriented programming is the most preferred programming technique now a day only due to the flexibility of re usability. Re usability is actually an attribute that makes the object oriented programming more flexible and attractive.

As this programming is based on objects. Object is actually a collection of data and functions that are used to operate on that data. These objects are defined as independent entities because the data inside each object represents the attributes of object and functions are used to change these attributes as required by a program.

These objects act just like spare parts of any program. Thus, they are not limited to any specific program; rather they can be used in more than one application as required.
These objects are defined as an independent entity in a program, and afterward they can be used in any other program that needs the same functionality. This reuse of objects helps in reducing the development time of programs.



Example:


Inheritance in Java refers to the feature wherein the code/functionality of one class can be used in another class that extends this class. Example:

public class Animal {
...
..
}

public class Cow extends Animal {
...
..
.
}

Here the class Child extends the class Parent and hence the methods of Parent are available for Child to use. This way we are re-using the code in the parent class in the child class instead of re-writing the whole thing again.

Comments

Popular posts from this blog

error: db5 error(11) from dbenv->open: Resource temporarily unavailable

If rpm command is not working in your system and it is giving an error message( error: db5 error(11) from dbenv->open: Resource temporarily unavailable ). What is the root cause of this issue? How to fix this issue?   just a single command- [root@localhost rpm]# rpm --rebuilddb Detailed error message- [root@localhost rpm]# rpm -q firefox ^Cerror: db5 error(11) from dbenv->open: Resource temporarily unavailable error: cannot open Packages index using db5 - Resource temporarily unavailable (11) error: cannot open Packages database in /var/lib/rpm ^Cerror: db5 error(11) from dbenv->open: Resource temporarily unavailable error: cannot open Packages database in /var/lib/rpm package firefox is not installed [root@localhost rpm]# RPM manage a database in which it store all information related to packages installed in our system. /var/lib/rpm, this is directory where this information is available. [root@localhost rpm]# cd /var/lib/rpm ...

Failed to get D-Bus connection: Operation not permitted

" Failed to get D-Bus connection: Operation not permitted " - systemctl command is not working in Docker container. If systemctl command is not working in your container and giving subjected error message then simple solution of this error is, create container with -- privileged option and also provide init file full path  /usr/sbin/init [root@server109 ~]# docker container run -dit --privileged --name systemctl_not_working_centos1 centos:7 /usr/sbin/init For detailed explanation and understanding I am writing more about it, please have look below. If we have a daemon based program(httpd, sshd, jenkins, docker etc.) running inside a container and we would like to start/stop or check status of daemon inside docker then it becomes difficult for us to perform such operations , because by default systemctl and service  commands don't work inside docker. Normally we run below commands to check services status in Linux systems. [root@server109 ~]# systemctl status ...

How to check rpm integrity?

This post will help you to get answers of below questions- How to check rpm integrity? How to check rpm authenticity? How to check rpm digital signature? What is gpgcheck? Let's take an example of below rpm package and see, how to verify if it is a genuine package? [root@localhost tmp]# ls -l vsftpd-2.2.2-11.el6.x86_64.rpm -r--r--r--. 1 root root 154392 Jan 27 10:27 vsftpd-2.2.2-11.el6.x86_64.rpm [root@localhost tmp]# There are multiple way to verify. 1. Verify using rpm [root@localhost tmp]# rpm -q vsftpd package vsftpd is not installed [root@localhost tmp]# [root@localhost tmp]# rpm -K vsftpd-2.2.2-11.el6.x86_64.rpm vsftpd-2.2.2-11.el6.x86_64.rpm: RSA sha1 ((MD5) PGP) md5 NOT OK (MISSING KEYS: (MD5) PGP#fd431d51) [root@localhost tmp]# If you want to see more details then use below options [root@localhost tmp]# rpm -vvK vsftpd-2.2.2-11.el6.x86_64.rpm D: loading keyring from pubkeys in /var/lib/rpm/pubkeys/*.key D: couldn't find any keys in /var/...