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Java
Tutotrial for [NLP-AI]
2
[email protected]
24 May 2017
1
Last Assignment
asgn1
asgn2
? Print the details in tabular format
- use tabs \t
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System.out.println("\"Can
we print '\\' with
System.out.println() statement?\"" );
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Java Tutorial series part 2
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Storing data
In Java, Data can be stored as
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Numbers
2, 6.67, 0.009
Characters
‘c’, ‘p’, ‘?’, ‘2’
Strings
“data”, “Hindi language”, “$99”, www.rediff.com
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int1
Program
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)
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Not executed
For documentation
Can be placed on any line
Anything written after // is not executed
E.g.
// this is a comment
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Used to explain/describe what is done in the
program
Good practice
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Types of numbers
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float1
int
Whole numbers like 0, 575, -345 etc.
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double
Numbers with decimal point
like 12.453, 3.432, 0.0000002
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Variable declaration
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Before using any name, it must be declared
(with its type i.e int or double).
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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
a
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Storage area
Java Tutorial series part 2
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int4
Assignment…
int a , b ;
a = 4;
b = 7;
a = b;
b = a;
a = 5;
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//
//
//
//
//
//
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
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char1
char2
Characters
‘a’, ‘A’, ‘c’ , ‘?’ , ‘3’ , ‘ ’
(last is the single space)
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Enclosed in single quotes
Character variable declaration
char ch;
Character assignment
ch = ‘k’;
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String data
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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
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Try to print these two figures on the screen using println and least number
of strings
*******
*****
***
*
***
*****
*******
**********
*
*
*
*
*
*
**********
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Java Tutorial series part 2
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Essential Linux commands
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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@tukaram lec2]$
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Create folder (directory)
mkdir <foldername>
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Goto that folder
cd <foldername>
cd
- To use or work into the folder
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Remove a folder
rmdir <foldername>
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list all file in the folder
ls
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Vi (Vim)
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Vi is notepad of Linux.
Used to write programs
Works in 2 modes
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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 …
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vi <filename>
To create a new file or existing file.
e.g. vi int1.java
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Before start typing, press ‘i’ to goto edit mode and type
the program.
To save program
Press escape and then these 2 characters “:w”
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To save and quit vi
Press escape and then these 3 characters “:wq”
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To quit vi without saving the latest changes
Press escape and then these 3 characters “:q!”
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Essential Linux commands
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rm <filename>
This command deletes the file specified
e.g. rm int1.class
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To log out press ‘ctrl-D’ at command prompt
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javac , java
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Thank you

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