“Introduction to Programming With Java”

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Lecture – 5

UMESH PATIL (umesh@cse.iitb.ac.in)

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• Quick recap of the syllabus covered so far.

• Solutions to previous assignments.

• Some programing practice.

• Introduction to Arrays.

Contents for Today’s Lecture

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Structure of Java Program:

class class-name { public static void main(String args[]) {

statements;

}}

Printing messages to the screen:

System.out.println(“Hello World”);System.out.print(“Hello World”);

Recap

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Data Types:Numbers – int (whole no.s), double (no.s with decimal point)

eg. int i = 23; double d = 33.23

Character – chareg. char c = ‘a’;

String – Stringeg. String s = “Hi”;

Boolean – booleaneg. boolean b = false;

Variable declaration:data-type variable-name

eg. int i = 23;

Recap…

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Expression: An expression is a combination of literals (like 100), operators (like +), variables and parentheses used to calculate a value. eg. 2 + 6 / (2 – 9)

Operators:Arithmetic – eg. ‘-’, ‘+’, ‘/’, ‘++’ etc.Relational –eg. ‘<’, ‘>=’, ‘!=’ etc.Conditional –eg. ‘&&’ (AND), ‘||’ (OR)

Control constructs like‘if’ and ‘if else’:

Recap…

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Write a program that averages the synsets created for three months April, May and June. Declare and initialize variable to the synset entered for each month. Compute the average and write out the results, something like this:Synsets Entered for April: 12 Synsets Entered for May : 14 Synsets Entered for June: 8 Average Synset Entered: 11.333333

Assignment

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class synset { public static void main(String args[]) { int april = 12; int may = 14; int june = 8; double avg; avg = ( april + may + june ) / 3.0;

System.out.println("Synsets Entered for April " + april); System.out.println("Synsets Entered for May " + may); System.out.println("Synsets Entered for June " + june); System.out.println("Average Synset Entered " + avg); }}

Solution

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int a_number=1; (range is 1 to 5 both including)

Print the value in a_number in word with and without using equality (= =) operator. For example it should print “Four” if a_number contains 4.

Assignment

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class assign1 { public static void main(String args[]) { int a_number; a_number = 5;

if(a_number == 1) System.out.println("One");

if(a_number == 2) System.out.println("Two");

if(a_number == 3) System.out.println("Three");

if(a_number == 4) System.out.println("Four");

if(a_number == 5) System.out.println("Five"); }

}

Solution

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Definition:

An array is a group/collection of variables of the same type that are referred to by a common name and an index

Examples:

• Collection of numbers

• Collection of names

• Collection of suffixes

Arrays

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Array of numbers:

Array of names:

Array of suffixes:

Examples

10 23 863 8 229

ment tion ness ves

Sholay Shaan Shakti

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Array is like a pen box with fixed no. of slots of same size.

Analogy

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Thank you…

End