introduction to programming using java - lecture 4

8/13/2019 Introduction to programming using JAVA - lecture 4

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Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.

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Introduction to ProgrammingIntroduction to Programming((Using Java)Using Java)

Nandika KasunNandika Kasun

University of Colombo School of Computing (UCSC)University of Colombo School of Computing (UCSC)

University of ColomboUniversity of Colombo

Sri LankaSri Lanka


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Control StatementsControl Statements

Control Statements

If ....Else Statements

if ( Expression )

statement1;

else

statement2;

If Expression true then statement1 is executed;

otherwise statement2 is executed. else is optional.


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If ..else statementsIf ..else statements

If more Statements are to be performed, all the

statements should be included within curly brackets.

If ( Expression) {

statement a;

statement b;}

else {

statement c;statement d;

}


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Conditional Operator ?:Conditional Operator ?:

Expression ? Statement 1 : Statement 2

If expression is true If expression is false

X= ((marks>50) ? Pass : Failed);


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The switch Statement

switch (Test) {case valueOne :

resultOne;

break;case valueTwo :

resultTwo;

break;

default : defaultResult;

}

Variable orExpression

that evaluates

tobyte,char orint

cannot be float,

long String

or any other

object


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7/20Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.

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The switch Statement contd..

Multiple statements within a case value can be used

without curly brackets

the test condition is limited to testing simple equality

unlike in if statements



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The do . while Statement

do {statement 1;

statement 2;..

..

statement n} while (Boolean expression)




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The do . while Statement contd..

The enclosed Statements will be executed

at least once irrespective of the Boolean

expressions result.

As long as the Boolean expressions yieldstrue the Statements will be repeated.

The curly brackets are not necessary for asingle Statement.




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Boolean

Expression ?

Statement 1;Statement 2;

..

Statement n;True

False

The do..whileLoop

do while statement




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The while Statement

while (Boolean expression) {statement 1;

statement 2;..

..

Statement n}




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The while Statement

TheBoolean expression is checked first.

If it yields true, Statements 1 to n areexecuted.

Boolean expression is once again checked. if yields true Statements are executed again.

This process is repeated tillBooleanexpression yields false.




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BooleanExpression ?

Statement 1;Statement 2;

..

Statement n;

True

False

The while Loop




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The for Statement

for (initilization; Boolean expression; increment) {

statement 1;

statement 2;..

..Statement n

}

If there is only

a single statementCurly brackets are

not necessary



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The for Statement

Initialization;Boolean Expression ;Increment)for (

Statement 1..

Statement n

{

1

4

3

2

false

true

5

Steps 3,4 & 5

is repeated till

expression becomes

false



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Jump StatementsJump Statements

break statementjumps out of a loop and effectively bypass

the loop condition.

continue statement

jumps out of the current iteration of the loop

return statement

terminates the method (function). Jumps to

the place immediately after the function call.

(break, continue,(break, continue, return)return)


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Labeled loops

A label breakstatement terminates the current

loop and proceeds to the first statement thatfollows the loop that is labeled by the identifierthat follows the keyword break.

for (int i=0; i


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RecursionRecursion

Methods that invoke themselves are known as

Recursive methods.

Recursion Example

class Factorial {

static long calcFact(int n) {

if n < 2

return 1;return n*calcFact(n-1);

{

}Recursive call


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RecursionRecursion

Class TestFactorial {public static void main (String args[ ]) {

System.out.print(Factorial of 5 is);

System.out.println( Factorial.calcFact(5));

}

}

To test the Factorial Class


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SummarySummary

Exercise:Exercise:

Implement a for loop using a while loopImplement a for loop using a while loopWrite a program which will display the followingsWrite a program which will display the followings

**

**********

********

**

******

**********

This week we learned control statements

introduction to programming using java - lecture 4

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