what is IOT?

How to name the domain?

How to name the domain?

If we can put the SEO keyword that related to our business is great. 

If you didn't find the good one and have no idea how to name the domain. 

This article is best suite s for you.

If we observe the Most of the successful companies like

1. microsoft

2. google

3. yahoo

4. twitter

5. facebook

6. netflix
7. infosys
8. wipro
9. salesforce

Common criteria of above names

1. easy to type
2. be memorable
3. pronounceable
4. two word pronunciation
  micro soft
  goo gle
  ya hoo
  twi tter
  face book
  net flix
  info sys
  wi pro
  sales force 

5. keep it short
  four letters to ten letter max.

To get the above common properties & to get the unique name I wrote the small snippet which prints the random name' s.

package hack.test.others;

import java.util.Random;

/** * Created by suresh on 14/2/17. */public class DomainSearch {
    public static void main(String[] args) {
        Random rand=new Random();
        int max=122;
        int min=97;

        int vowelMax=4;
        int vowelMin=0;

        char arr[]={'a','e','i','o','u'};
        for(int i=1;i<=1000;i++){

            System.out.println(arr[rand.nextInt((vowelMax-vowelMin)+1)+vowelMin]
                    +""+arr[rand.nextInt((vowelMax-vowelMin)+1)+vowelMin]
                    +""+(char)(rand.nextInt((max-min)+1)+min)
                    +""+arr[rand.nextInt((vowelMax-vowelMin)+1)+vowelMin]
                    +""+(char)(rand.nextInt((max-min)+1)+min)
                    +""+arr[rand.nextInt((vowelMax-vowelMin)+1)+vowelMin]
                    +""+arr[rand.nextInt((vowelMax-vowelMin)+1)+vowelMin]
                    +""+(char)(rand.nextInt((max-min)+1)+min));
        }
    }
}

How to generate GPG Key?

Prerequisites

packages to be installed

1. rngd
2. gpgv OR gpgv2

Step1: Create a Temporary Folder and CD to it

Step2: Generate GPG Key

1. eval `gpg-agent --daemon --no-grab --write-env-file $HOME/.gpg-agent-info`
2. export GPG_TTY=`tty`
3. export GPG_AGENT_INFO
4. gpg --gen-key
1. Enter passphrase: ******
5. Run in a Different terminal rngd -f -r /dev/urandom

Step3: read the key' s.

 gpg -k

Sample Output:

GPG Key o/p:

.......+++++

+++++

We need to generate a lot of random bytes. It is a good idea to perform

some other action (type on the keyboard, move the mouse, utilize the

disks) during the prime generation; this gives the random number

generator a better chance to gain enough entropy.

.+++++

.................+++++

gpg: key 50F6E79D marked as ultimately trusted

public and secret key created and signed.

gpg: checking the trustdb

gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model

gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u

pub   2048R/50F6E79D 2015-08-14

Key fingerprint = 3C2C 81AA 5B9E 6772 1AEA  9AF3 78B2 D37D 50F6 E79D

uid ZeroOnePrograms  <developer@zerooneprograms.com>

sub   2048R/EA01868C 2015-08-14

How to create debian package without tarball file?

Prerequisites

1. Installed packages 
1. build-essential
2. fakeroot
3. devscripts
4. gnupg-agent
5. debhelper
6. dh_make

Notes:

1. This tutorial is useful to develop a quick Debian package example.
2. This tutorial doesn't have any explanation' s for 
1. Debian rules.
2. Various Debian build stage' s.
3. license creation and attaching to Debian package.
4. Debian man pages creation& integrating to the Debian package.
5. Debian package creation from existing tarball.
6. how to write debian package build changes.
7. gpg key for Debian Package

Step1: add Debian Package default Name, Email-Id to global environment variables /etc/environment.

DEBEMAIL="developer@zerooneprograms.com"
DEBFULLNAME="zerooneprograms"
EMAIL="support@zerooneprograms.com"

Step2: add Debian Package Name, installation script file name, HOME Folder Path for Script& Package Version.

SOURCEBINPATH=$(pwd)
SOURCEBIN=zerooneprograms
DEBFOLDER=zerooneprograms
DEBVERSION=1.0

Step3: Create Folder Debian Package with below  naming Conventions

DEBFOLDERNAME=$DEBFOLDER-$DEBVERSION

# Create your scripts source dir
mkdir $DEBFOLDERNAME

Step4: Copy the installation script file to the Debian Package HOME Folder.

# Copy your script to the source dir
cp $SOURCEBINPATH/$SOURCEBIN $DEBFOLDERNAME
cd $DEBFOLDERNAME

Step5: Create Sample Files& Folder/ Skeleton from Standard Debian Package Format.

# Create the packaging skeleton (debian/*)
dh_make  -s --indep --createorig

|-- debian

|   |-- rules

|   |-- copoyright

|   |-- control

|   |-- changelog

|   |-- patches

|   |-- source

|   `-- upstream

|-- doc

|   |-- man

|   |   `-- fr

|   |-- syntax

|   `-- texinfo

|-- m4

|-- po

`-- src

Step6: Change the script files for below, based on package requirements

1. add zerooneprograms script file to root folder 
2. preinstallation scripts
3. post installation scripts
4. pre remove scripts
5. post remove scripts
6. control file
7. rules

echo "\nchange control file, preins, postins,prerm and postrm and hit the <Enter> with any key"
read temp

Step7: Create custom Linux terminal commands,  debian/install has instructions to create File& Folder' s while installing the package. Below line will add the file zerooneprograms script in /usr/bin, which creates a terminal command.
echo $SOURCEBIN usr/bin > debian/install

add the instructions to create Folder' s and to copy the files& Folder to the Specific path.

Step8: Remove the all unnecessary files 
# Remove the example files
rm debian/*.ex

Step9: Remove the all unnecessary files 
dpkg-buildpackage -uc -us   #without key


Example Script for creating the debian package  create.sh 

#!/bin/bash
# Configure your paths and filenames
SOURCEBINPATH=$(pwd)
SOURCEBIN=zerooneprograms
DEBFOLDER=zerooneprograms
DEBVERSION=1.0


DEBFOLDERNAME=$DEBFOLDER-$DEBVERSION

# Create your scripts source dir
mkdir $DEBFOLDERNAME

# Copy your script to the source dir
cp $SOURCEBINPATH/$SOURCEBIN $DEBFOLDERNAME
cd $DEBFOLDERNAME

# Create the packaging skeleton (debian/*)
dh_make  -s --indep --createorig

echo "\nchange control file, preins, postins,prerm and postrm and hit the <Enter> with any key"
read temp

# Remove make calls
#grep -v makefile debian/rules > debian/rules.new
#mv debian/rules.new debian/rules

#mkdir -p debian/tmp

#cp $SOURCEBINPATH/$SOURCEBIN  debian/tmp/
# debian/install must contain the list of scripts to install
# as well as the target directory
echo $SOURCEBIN usr/bin > debian/install
#echo test opt >> debian/install

# Remove the example files
rm debian/*.ex

# Build the package.
# You  will get a lot of warnings and ../somescripts_0.1-1_i386.deb
#debuild -S -rfakeroot -k<gpg_key_id>

#debuild -S -rfakeroot -k50F6E79D
#(or)
dpkg-buildpackage -uc -us   #without key

Example rules for Debian Package Creation

#!/usr/bin/make -f

# -*- makefile -*-

# Uncomment this to turn on verbose mode.

#export DH_VERBOSE=1

#%:

# dh $@

clean:

dh_testdir

dh_testroot

rm -f build-stamp configure-stamp

install: build

dh_testdir

dh_testroot

dh_clean -k 

dh_installdirs

# Add here commands to install the package into debian/flare.

install -d debian/opt/ZeroOnePrograms

cp -r $(CURDIR)/../ZeroOnePrograms    $(CURDIR)/debian/zerooneprograms/opt

# Sample RULE's

# install -m 755 $(DISTSDIR)/*              $(CURDIR)/debian/tmp/opt/

# bunzip2                          $(CURDIR)/debian/tmp/usr/share/doc/debian-book/*pdf*.bz2

# install -m 644 $(DISTSDIR)/*latex*.bz2    $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# cp -r          $(SRCDIR)/htmlsplit        $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# install -m 644 $(CURDIR)/debian/copyright $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# install -m 644 $(SRCDIR)/*.html           $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# install -m 644 $(SRCDIR)/*.css            $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# cp -r          $(SRCDIR)/images           $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# cp             $(CURDIR)/LICENSE          $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# cp             $(CURDIR)/AUTHORS          $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# gzip           $(CURDIR)/debian/tmp/usr/share/doc/debian-book/AUTHORS

# cp             $(CURDIR)/README           $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# gzip           $(CURDIR)/debian/tmp/usr/share/doc/debian-book/README

# cp             $(CURDIR)/TODO             $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# gzip           $(CURDIR)/debian/tmp/usr/share/doc/debian-book/TODO

# cp             $(CURDIR)/README.Debian    $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# gzip           $(CURDIR)/debian/tmp/usr/share/doc/debian-book/README.Debian

# cp             $(CURDIR)/ChangeLog        $(CURDIR)/changelog

# mv             $(CURDIR)/changelog        $(CURDIR)/debian/tmp/usr/share/doc/debian-book/

# Build architecture-independent files here.

binary-indep: build install

# We have nothing to do by default.

# Build architecture-dependent files here.

binary-arch: build install

dh_testdir

dh_testroot

dh_installchangelogs 

# dh_installdocs --exclude=CVS

# dh_installexamples

dh_install

# dh_installmenu

# dh_installdebconf

# dh_installlogrotate

# dh_installemacsen

# dh_installpam

# dh_installmime

# dh_installinit

# dh_installcron

# dh_installinfo

# dh_installman

dh_link

# dh_strip

dh_compress --exclude=.pdf --exclude=LICENSE

dh_fixperms

# dh_perl

# dh_python

# dh_makeshlibs

dh_installdeb

# dh_shlibdeps

dh_gencontrol

dh_md5sums

dh_builddeb

binary: binary-indep binary-arch

.PHONY: build clean binary-indep binary-arch binary install configu 

Reference

https://www.debian.org/doc/manuals/maint-guide/build.en.html

http://tldp.org/HOWTO/html_single/Debian-Binary-Package-Building-HOWTO/

How to Validate SSL Certificates with bash script?

Prerequisites

1. SSL Certificates
2. OpensSSL to be Installed

Step1: Prompt for the SSL Certificates File Paths

echo "Reference"
echo "---------"
echo "enduser-example.com.crt
enduser-example.com.key
enduser-example.com.chain"
echo ""
echo ""
echo "Please Provide full Path for Certificate (enduser-example.com.crt)"

            if [ -e $PATH_CERT_FILE ];then
                    #Do Nothing
               echo ""
            else
                    echo "Wrong Path"
                exit 1
            fi

echo "Please Provide full path for Intermediate Certificate (enduser-example.com.chain|gd_bundle.crt)"
            read PATH_INTERMEDIATE_CERT
                        if [ -e $PATH_CERT_FILE ];then
                                #Do Nothing
                                echo ""
                        else
                                echo "Wrong Path"
                                exit 1
                        fi

echo "Please Provide the full path for Private Key File(enduser-example.com.key)"
            read PATH_KEY_FILE
                        if [ -e $PATH_CERT_FILE ];then
                                #Do Nothing
                                echo ""
                        else
                                echo "Wrong Path"
                                exit 1
                        fi

Step2: validate the certificates with OpenSSL tool

#Validating Certificates

_status=$(openssl verify -CAfile $PATH_INTERMEDIATE_CERT  $PATH_CERT_FILE | grep OK)

            result=$(echo $_status | cut -f2 -d ':')

            if [ "$result" != " OK" ]; then

                echo "Please Verify The Certificates and Try Again.."

                exit 1

            fi

How to change VHost Name & respective SSL Certificates with Bash Script?

Step1: change the VHost ServerName/Domain Name with sed

sed -i "s@OldDomain.*@NewDomain@g"

Step2: Prompt for the New Certificates Absolute Path& Validate them from above Procedure

Step3: On Successful validation, copy the certificate files to new Folder.

            #Configuring the Certificates

            _date=$(date +"%H%M%S")

            mkdir -p /etc/apache2/$_date

            echo $_date

            cp $PATH_CERT_FILE    /etc/apache2/"$_date"/

            cp $PATH_INTERMEDIATE_CERT /etc/apache2/"$_date"/

            cp $PATH_KEY_FILE  /etc/apache2/"$_date"/       

Step4: Copy the absolute path of each certificate to a variable.

            _CERT_FILE=$(echo "$PATH_CERT_FILE"| rev |cut -f1 -d '/' |rev)

            NEW_PATH_CERT_FILE=/etc/apache2/"$_date"/"$_CERT_FILE"

                _INTERMEDIATE_CERT_FILE=$(echo "$PATH_INTERMEDIATE_CERT"| rev |cut -f1 -d '/' |rev)

            NEW_PATH_INTERMEDIATE_CERT=/etc/apache2/"$_date"/"$_INTERMEDIATE_CERT_FILE"

            _KEY_FILE=$(echo "$PATH_KEY_FILE"| rev |cut -f1 -d '/' |rev)    

            NEW_PATH_KEY_FILE=/etc/apache2/"$_date"/"$_KEY_FILE"

Step5: Replace the SSL File Paths in Apache Configuration files.

            #Seetting New SSL Paths in Apache Configuration

            sed -i "s@SSLCertificateFile.*@SSLCertificateFile  $NEW_PATH_CERT_FILE@g"  /etc/apache2/sites-available/zerooneprograms.conf

            sed -i "s@SSLCertificateKeyFile.*@SSLCertificateKeyFile  $NEW_PATH_KEY_FILE@g"  /etc/apache2/sites-available/zerooneprograms.conf

            sed -i "s@SSLCertificateChainFile.*@SSLCertificateChainFile  $NEW_PATH_INTERMEDIATE_CERT@g"  /etc/apache2/sites-available/zerooneprograms.conf

Step6: Check the Apache Syntax and restart the web server.

How to check prerequisite in linux bash script?

Check the user is root or not?

if [ "$(whoami)" != 'root' ]; then
        echo "You have no permission to run $0 as non-root user."
        exit 1
fi

Check the OS?

OS=`cat /etc/issue |head -n 1 |awk '{ print $1 }'`

if [ $OS != "Ubuntu" ]; then

          echo "OS Architecture Not Supported...!"

       exit 1

fi

Check the VCPU' s?

vcpu=$(lscpu | grep "^CPU(s):.*$"|awk '{print $2}')
if [ $vcpu -lt 2 ];then
        echo "Minimum 2 vcpu's are Required...!"
        exit 1
fi

Check the Total Memory/RAM?

TotalMemory=$(grep MemTotal /proc/meminfo | awk '{print $2}')

if [ $TotalMemory -lt 8113442 ];then
        echo "Insuffiecient Memory 'Total RAM Should be 8G'"
        exit 1
fi

<<'COMMENT'
Total Memory        -  8G/100%  -   8388608KB
Operational Memory  -  .30%     -   25165.824KB
Remaining           -  99.7%    -   8363442.176
Required            -  6G/100%  -   6291456KB
COMMENT

Check the Available Memory/RAM?

FreeMemory=$(grep MemFree: /proc/meminfo |awk '{print $2}')
if [ $FreeMemory -lt 6291456 ];then
       echo "Insuffiecient Memory 'Require 6G Free Memory'"
       exit 1
fi

Check the any other installation' s are in progress?

if lsof /var/lib/apt/lists/lock >>/dev/null 2>&1 ;then
                echo "/var/lib/apt/lists/lock  locked"
                exit 1
fi

if lsof /var/lib/dpkg/lock >>/dev/null 2>&1 ;then
                echo "/var/lib/dpkg/lock  locked"
                exit 1
fi

Check the availability of Port?

nc -z 127.0.0.1 80;

if test "$?" -eq "0"  #if port 80 is in Listening mode
then
        echo "Port 80 is not available."
        exit 1
fi


Note: Tested under Ubuntu 12.x& 14.x

How to repair the MongoDB with bash script?

repair_and_restart_mongod(){

  if [ -f /etc/default/mongodb ]; then . /etc/default/mongodb; fi

  ENABLE_MONGODB="yes"
  if [ "x$ENABLE_MONGODB" = "xyes" ]; then
        if [ -f $MONGODB_HOME/mongod.lock ]; then
                rm $MONGODB_HOME/mongod.lock >> /dev/null
                sudo -u mongodb /usr/bin/mongod --config /etc/mongodb.conf --repair >> /dev/null
        fi
        #exec start-stop-daemon --start --quiet --chuid mongodb --exec  /usr/bin/mongod -- --config /etc/mongodb.conf
        service mongodb start >> /dev/null  2>&1
  fi
}

Tested under Ubuntu Server 12.x& 14.x

How to check the MongoDB Status in bash script?

is_mongod_running(){
PID=$(cat $MONGODB_HOME/mongod.lock)
        status=$(service mongodb status 2>&1)
        echo $status | grep -q "mongodb start/running, process.*"

        if [ $? -eq 0 ] && [ "x$PID" != "x" ] ;then     #&& kill -0 $PID 2>/dev/null; then
                _status=0 #echo "mongod is running"
        else
                _status=1 #echo "mongod is not running"
        fi
        return $_status
}


Note: Tested under Ubuntu Server 2.x& 14.x

How to check the Apache Tomcat Status with bash script?

##check the status of tomcat
is_tomcat_running(){
        PID=$(cat $TOMCAT/conf/catalina.pid 2>&1)
        if [ "x$PID" != "x" ]&& kill -0 $PID 2>/dev/null; then
                _status=0 #echo "tomcat already running"
        else
                _status=1 #echo "tomcat is not running"
        fi
        return $_status
}

How to stop the Tomcat with bash script?

stop() {
  pid==$(cat $TOMCAT/conf/catalina.pid 2>&1)
  if [ -n "$pid" ]
  then
    echo -e "\e[00;31mStoping Tomcat\e[00m"
    #/bin/su -p -s /bin/sh $TOMCAT_USER
        sh $CATALINA_HOME/bin/shutdown.sh

    let kwait=$SHUTDOWN_WAIT
    count=0;
    until [ `ps -p $pid | grep -c $pid` = '0' ] || [ $count -gt $kwait ]
    do
      echo -n -e "\n\e[00;31mwaiting for processes to exit\e[00m";
      sleep 1
      let count=$count+1;
    done

    if [ $count -gt $kwait ]; then
      echo -n -e "\n\e[00;31mkilling processes didn't stop after $SHUTDOWN_WAIT seconds\e[00m"
      terminate
    fi
  else
    echo -e "\e[00;31mTomcat is not running\e[00m"
  fi

  return 0
}

Note: We need to kill/terminate the tomcat if it is failed to shutdown with in the given period of time& we need to clear the PID.

How to check Apache Web Server Status in Ubuntu with bash script?

##Check Apache Web Server running
is_apache_running(){
        a=$(service apache2 status) >> /dev/null
        if [ "$a" = " * apache2 is running" ];
        then
                _status=0  #echo "Apache WebServer Already Running"
        else
                _status=1  #echo "Apache WebServer is not Running"
        fi
        return $_status
}

##Check Apache Syntax
is_apache_syntax_ok(){

_syntax=$(apache2ctl -t 2>&1)

if [ "$_syntax" = "Syntax OK" ]; then
         _syntax_ok=0
else
         _syntax_ok=1
fi
        return  $_syntax_ok
}

Above snippet is tested under Ubuntu Server 12.x & 14.x.

How to validate Fully Qualified Domain with bash script?

#!/bin/bash

fqdn="www.google.com"

#FQDN Validation
{
        echo $fqdn | grep -P "^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$"
} && {
        echo "valid FQDN"  
} || {
        echo "Invalid FQDN Address"
exit 1
}

How to validate the email with bash script?

If else structure created with shell script operators

{

// shell script snippet A

} && {

// shell script snippet B

} || {

//shell script snippet C

}

snippet A executes, B will execute upon successful execution of script A & C will execute upon unsuccessful execution of script A.

grep is a linux command based tool to search the string match pattern' s where -E option for extended regular expression evaluation.

#!/bin/bash
email="test@gmail.com"

#Email Validation
{
echo  | grep -E "^[a-z0-9!#\$%&'*+/=?^_\`{|}~-]+(\.[a-z0-9!#$%&'*+/=?^_\`{|}~-]+)*@([a-z0-9]([a-z0-9-]*[a-z0-9])?\.)+[a-z0-9]([a-z0-9-]*[a-z0-9])?\$"
} && {
echo "Valid E-Mail Address"
} || {
echo "Invalid E-Mail Address"
exit 1
}

How to read a file using BufferedInputStream?

1. File Class is used for file operation like creating a file, reading a file, updating a file, deleting a file, creating of directories, file search operations.
2. FileInputStream Class used for reading bytes from a file in a file system. This Class is useful for reading the stream of bytes, raw data like image& etc. FileReader Class is useful to read the stream of characters.
3. BufferedInputStream  Class is extended with FileInputStream& added with additional functionality of store stream in a Buffer. With Buffer, we can do the operations like read stream, skip the bytes, mark, reset, update the stream as needed, ready with next byte and updating the stream as needed.

Read File Using Java BufferedInputStream Example.

This example shows how to read a file using available and read methods of Java BufferedInputStream.

package snippets11;

import java.io.*;

/**

 * Created by root on 15/3/16.

 */

public class ReadFileUsingBufferedInputStream {

    public static void main(String[] args) {

        File file=null;

        FileInputStream in=null;

        BufferedInputStream bf=null;

        try {

            file=new File("/home/suresh/temp/testjava.txt");

            in=new FileInputStream ( file );

            bf=new BufferedInputStream ( in );

            /*

             * BufferedInputStream has ability to buffer input into

             * internal buffer array.

             *

             * available() method returns number of bytes that can be

             * read from underlying stream without blocking.

             */

            //read file using BufferedInputStream

            while (bf.available ()>0){

                System.out.print((char)bf.read());

            }

        } catch (FileNotFoundException e) {

            e.printStackTrace ( );

        } catch (IOException e) {

            e.printStackTrace ( );

        }finally {

            //close the BufferedInputStream using close method

            try{

                if(bf != null)

                    bf.close();

            }catch(IOException ioe)

            {

                System.out.println("Error while closing the stream : " + ioe);

            }

        }

    }

}

How to read byte array using ByteArrayInputStream?

ByteArrayInputStream keep maintains a buffer and tracks the next byte to be supplied. With ByteArrayInputStream we can read bulk data and buffer is helpful for faster response.


Example Code:

package snippets11;
import java.io.ByteArrayInputStream;

/**
 * Created by root on 15/3/16.
 */
public class ByteArrayInputStreamExample {
    public static void main(String[] args) {
        String string="Programming World...";
        byte[] bytes=string.getBytes();

        ByteArrayInputStream ba=new ByteArrayInputStream(bytes);
        int ch;
        while((ch=ba.read())!=-1){
            System.out.print((char)ch);
        }
    }
}

click here.

basic data types in java

Data types in java are two type' s

1. Primitive 
2. Reference

Mostly Used Primitive Data Type' s

1. boolean 
2. char
3. int
4. byte
5. float
6. long
7. double
8. String

Data Type: boolean

Bytes: 1 bit.

Description: this data type represents 1 bit information, mostly used in the true/false conditions.

Possible values: true/false 

Data Type: char

Bytes: 16 bit unicode.

Description: this data type used to store character' s.

Data Type: int 

Bytes: 32 bit signed representation.

Description: this data type used to store integer of signed representation.

Data Type: byte 

Bytes: 8 bit signed representation.

Description: this data type used to store integer of signed representation, this type is useful when we need to store an array of integer's with max of 8 bit' s. so, we can save 24 bit' s when compare to the int data type.

Data Type: float 

Bytes: 32 bit

Description: this data type used to store integer with single-precision/decimal values.

Data Type: long

Bytes: 64 bit signed representation.

Description: this data type used to store integer with single-precision/decimal values.

Data Type: double

Bytes: 64 bit signed representation.

Description: this data type used to store integer with single-precision/decimal values.

Data Type: String

Bytes: 64 bit signed representation.

Description: this data type used to store integer with single-precision/decimal values.

Example code:

package snippets1;

/**

 * Created by root on 11/3/16.

 */

public class DataTypeTest {

    public static void main(String args[]){

        boolean status = true;

        char a = 'A';

        int b = 12;

        byte e = 12;

        float f=3.14f;

        long c = 1235;

        double d = 12345.23;

        String str = "programming";

        System.out.println("boolean: "+status+"\nchar: "+a+"int: "+b+"\nbyte: "+e+"\nfloat: "+f+"\nlong: "+c+"\ndouble: "+d);

    }

}

Command line example in java

Passing command line arguments in java

1. check the number argument's passed, exit the program with status success when you received insufficient command line arguments.

        if(args.length==0){

            System.out.println("Insufficient Arguments..");

            System.exit(0);

        }

2.  Parse the arguments to Integer from String.

      System.out.print("sum="+Integer.parseInt(arg1)+Integer.parseInt(arg2));

for complete code click here.