Java Tutotrial for NLPAI 2

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JavaTutotrial for NLP-AI2

• ashishfa_at_cse.iitb.ac.in

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Last Assignment
asgn1 asgn2

• ? Print the details in tabular format
• - use tabs \t
• System.out.println("\"Can we print '\\' with
  System.out.println() statement?\"" )

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Storing data

• In Java, Data can be stored as
• Numbers
• 2, 6.67, 0.009
• Characters
• c, p, ?, 2
• Strings
• data, Hindi language, 99, www.rediff.com

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Program
int1 int2

• // this program will declare and print a number
• class int2
• public static void main(String
  arguments)
• int weight 68
• System.out.println("your weight
  is " weight)
• //end of program

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Comments(double slash)

• Not executed
• For documentation
• Can be placed on any line
• Anything written after // is not executed
• E.g.
• // this is a comment
• Used to explain/describe what is done in the
  program
• Good practice

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Types of numbers
float1

• int
• Whole numbers like 0, 575, -345 etc.
• double
• Numbers with decimal point
• like 12.453, 3.432, 0.0000002

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Variable declaration

• Before using any name, it must be declared
• (with its type i.e int or double).
• Needed only once in one program
• Generally, done initially
• Syntax
• datatype name
• double total // stores the total value
• int index
• int a,b , c, sum, interest

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Assignment
int3 int5

• int a //declaration needed once
• a 10 // assignment declared above
• int a 10 // assignment and declaration
  together
• 10 a // not possible compilation error
• Left hand side is always a variable for assignment

Storage area
a
10
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Assignment
int4

• int a , b
• a 4
• b 7
• a b
• b a
• a 5

// a ? b ? // a 4 b ? // a 4
b 7 // a 7 b 7 // a 7 b 7 //
a 5 b 7
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Character data
char1 char2

• Characters
• a, A, c , ? , 3 ,
• (last is the single space)
• Enclosed in single quotes
• Character variable declaration
• char ch
• Character assignment
• ch k

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String data
string1 string2 string3

• Strings are sequence of characters enclosed in
  double quotes
• Declaration
• String name
• String address
• String line
• Assignment
• name ram
• line this is a line with spaces
• name a // single character can be stored
• name // empty string
• The sequence of characters enclosed in double
  quotes, printed in println() are also strings.
• E.g. System.out.println( Welcome ! )

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Practice problem

• Try to print these two figures on the screen
  using println and least number of strings

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Essential Linux commands

• Use tukaram(10.144.22.105) or any other linux
  machine
• Type javac and java, to verify if java is
  installed and working properly.
• Login to tukaram
• ashish_at_tukaram lec2
• Create folder (directory)
• mkdir ltfoldernamegt
• Goto that folder
• cd ltfoldernamegt
• cd
• - To use or work into the folder
• Remove a folder
• rmdir ltfoldernamegt
• list all file in the folder
• ls

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Vi (Vim)

• Vi is notepad of Linux.
• Used to write programs
• Works in 2 modes
• Command mode
• - While in vi, press escape to go to command
  mode
• Edit mode
• - while in vi, if you are in command mode, press
  i on keyboard once to go to edit mode .

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Vi

• vi ltfilenamegt
• To create a new file or existing file.
• e.g. vi int1.java
• Before start typing, press i to goto edit mode
  and type the program.
• To save program
• Press escape and then these 2 characters w
• To save and quit vi
• Press escape and then these 3 characters wq
• To quit vi without saving the latest changes
• Press escape and then these 3 characters q!

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Essential Linux commands

• rm ltfilenamegt
• This command deletes the file specified
• e.g. rm int1.class
• To log out press ctrl-D at command prompt
• javac , java

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Thank you

• ?