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8/13/2019 Introduction to programming using JAVA - lecture 4
1/20
Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
1
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
8/13/2019 Introduction to programming using JAVA - lecture 4
2/20
Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
2
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.
8/13/2019 Introduction to programming using JAVA - lecture 4
3/20
Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
3
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;
}
8/13/2019 Introduction to programming using JAVA - lecture 4
4/20
Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
4
Conditional Operator ?:Conditional Operator ?:
Expression ? Statement 1 : Statement 2
If expression is true If expression is false
X= ((marks>50) ? Pass : Failed);
8/13/2019 Introduction to programming using JAVA - lecture 4
5/20
Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
5
Control StatementsControl Statements
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
8/13/2019 Introduction to programming using JAVA - lecture 4
6/20
8/13/2019 Introduction to programming using JAVA - lecture 4
7/20Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
7
Control StatementsControl Statements
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
8/13/2019 Introduction to programming using JAVA - lecture 4
8/20Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
8
The do . while Statement
do {statement 1;
statement 2;..
..
statement n} while (Boolean expression)
Control StatementsControl Statements
8/13/2019 Introduction to programming using JAVA - lecture 4
9/20Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
9
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.
Control StatementsControl Statements
8/13/2019 Introduction to programming using JAVA - lecture 4
10/20Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
10
Boolean
Expression ?
Statement 1;Statement 2;
..
Statement n;True
False
The do..whileLoop
do while statement
Control StatementsControl Statements
8/13/2019 Introduction to programming using JAVA - lecture 4
11/20Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
11
The while Statement
while (Boolean expression) {statement 1;
statement 2;..
..
Statement n}
Control StatementsControl Statements
8/13/2019 Introduction to programming using JAVA - lecture 4
12/20Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
12
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.
Control StatementsControl Statements
8/13/2019 Introduction to programming using JAVA - lecture 4
13/20Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
13
BooleanExpression ?
Statement 1;Statement 2;
..
Statement n;
True
False
The while Loop
Control StatementsControl Statements
8/13/2019 Introduction to programming using JAVA - lecture 4
14/20Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
14
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
Control StatementsControl Statements
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.
15
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
Control StatementsControl Statements
8/13/2019 Introduction to programming using JAVA - lecture 4
16/20
Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
16
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)
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.
17
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
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.
18
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
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.
19
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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Kasun@[email protected] 2003. All rights reserved. No part of this material may be reproduced and sold.
20
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