bung Softwareentwicklung 1 fr Wirtschaftsinformatik bung 5

1
Übung Softwareentwicklung 1für
Wirtschaftsinformatik Übung 5

• Ismail Khalil Ibrahimismail_at_tk.uni-linz.ac.atht
  tp//www.tk.uni-linz.ac.at/teaching/

2
Control Structures

• In any programming language, there are three
  fundamental patterns for controlling the flow of
  the program execution called control structures
• sequence
• program statements are executed sequentially
• also called straight-line programming
• decision (a.k.a selection)
• The flow of the program statements is altered
  depending on one or more conditions
• It is implemented in Java using if, if/else, and
  switch statements
• iteration
• Is a repetition control structure
• It is implemented in Java using while, do/while,
  and for statements

3
The if Statement
test expression
if statements
true
if
false
Boolean decision operation
Processing Statements
next statements
if (test expression) statement
1 statement 2 //COMPOUND STATEMENTS statem
ent n //END IF
4
Example
if ((xlty) (y!10)) int sum
xy System.out.println(x x) System.out.print
ln(y y) System.out.println(sum sum)
5
The if/else Statement
if statements
true
test expression
next statements
if
false
else statements
else
6
The if/else Statement
if (test expression) Statement
1 Statement 2 Statement n //END
IF else Statement 1 Statement
2 Statement n //END ELSE
7
Example
String s1Andy String s2Janet if
(s1.equals(s2)) System.out.println(the strings
are equal) else System.out.println(the strings
are not equal)
8
Nested ifs
temp gt 0
true
false
ice
temp gt 100
false
true
steam
water
9
Example
if (year 1) System.out.println(Freshman) if
(year 2) System.out.println(Sophomore) if
(year 3) System.out.println(Junior) if
(year 4) System.out.println(Senior) if
(year gt 4) System.out.println(Graduate)
if (year gt 4) System.out.println(Graduate) else
if (year gt 3) System.out.println(Senior) else
if (year gt 2) System.out.println(Junior) else i
f (year gt 1) System.out.println(Sophomore) else
System.out.println(Freshman)
10
Example
if (year gt 1) if (year gt 2) if (year gt 3)
if (year gt 4) System.out.println(Gradu
ate) else System.out.println(Senior)
else System.out.println(Junior) else
System.out.println(Sophomore) else
System.out.println(Graduate)
11
The switch statement
selector case 1
true
case 1 statements
switch
break
false
selector case 2
true
case 2 statements
break
false
selector case n
true
case n statements
break
false
optional default statements
next statements
12
The switch statement
switch(selector variable) case case 1
value case 1 statements break case case 2
value case 2 statements break case
case n value case n statements break //EN
D SWITCH
13
Example
switch(letterGrade) case A
System.out.println(Excellent) break case
B System.out.println(Superior) break cas
e C System.out.println(Average) break ca
se D System.out.println(Poor) break case
E System.out.println(Try Again) break
14
The default option
switch(selector variable) case case 1
value case 1 statements break case case 2
value case 2 statements break case
case n value case n statements break defaul
t default statements //END SWITCH
15
Example
switch(letterGrade) case a case A
System.out.println(Excellent) break case
b case B System.out.println(Superior) b
reak case c case C System.out.println(Aver
age) break case d case D
System.out.println(Poor) break case
e case e System.out.println(Try
Again) break default System.out.println(No
match found for letterGrade)
16
Looping Operations Iteration

• Iteration control structure causes the program
  flow to go around in a loop
• To prevent infinite looping, all iteration
  control structures test a condition to determine
  when to exit the loop
• There are three kinds of tests
• Pretest test a condition before before each loop
  is executed
• Posttest test a condition after each loop is
  executed
• Fixed repetition the loop is executed for a
  predetermined number of times

17
The while loop
test expression
false
while
true
loop body
while (test expression) statement
1 statement 2 //LOOP BODY statement
n //END WHILE
18
Example
int number 5 int sum 0 while(numbergt0) sum
number --number System.out.println(the sum
is sum)
19
The do/while loop
do statement 1 statement
2 //LOOP BODY statement n //END
DO/WHILE while (test expression)
loop body
do
while
test expression
false
true
20
Example
int number 5 int sum 0 do sumnumber --n
umber while(numbergt0) System.out.println(the
sum is sum)
21
The for loop
test expression on counter
initialize counter value
false
for
true
Loop body
for (int counter initial value counter test
expression increment/decrement counter)
statement 1 statement 2 //LOOP
BODY statement n //END FOR
Increment/ decrement counter
22
Example
System.out.println(\n\tNumber\tSquare\tCube) Sy
stem.out.println(\t------\t------\t------) for(i
nt count 1 count lt11 count) System.out.print
ln(\t count \t countcount \t
countcountcount)
23
The break statement
while (test expression) statement
1 Statement 2 if (test expression) break
statement n //END WHILE NEXT STATEMENT
AFTER WHILE
24
The break statement
int number 1 while (number lt 11) if (number
5) break System.out.println(number now is
number) number System.out.println(The
loop is terminated and the number is number)
25
The continue statement
for (counter initial value counter test
expression increment/decrement counter)
statement 1 statement 2 if (test
expression) continue statement n //END
FOR NEXT STATEMENT AFTER FOR
26
Example
int value 0 for(int number1numberlt11number
) if(number5) continue System.out.println(nu
mber now is number) valuenumber System.out.
println(The loop is terminated and the number
is number)
27
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