Control Structures

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Control Structures
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Sequential Execution
x keyBoard.nextInt()
statement
statement
y 2x - 3
statement
System.out.println(x)


System.out.println(y)
statement
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Selecting Execution Route
?
true
statement
false
if(?) statement
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Selecting Execution Route
?
true
statement _1
false
statement_2
if(?) statement_1else statement_2
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for Loops
Initializecounter

• Referred to as the counting loop
• Parts of a for-loop
• Initialize and declare counter section
• Test counter section
• Update counter section
• Loop body section

Test counter
false
true
statement
Updatecounter
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for Loops
for(initialize test update) body
for(initialize_variable test_variable
change_variable) //body of loop goes
here
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while loop
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//display all divisors of a given positive
integer //N positive integer //d is a divisor
of N input N d 1 while d less than or equal
to N if(d divides evenly into N)
print d increment d by one
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input N d 1 while d less than or equal to N
if(d divides evenly into N) print d
increment d by one
Bench
Test N d d lt N? d divdes
N? output
10 1
yes yes 1
--------------------------------------------------
----------- 2 yes
yes 2 -----------------------------
-------------------------------- 3
yes no -
--------------------------------------------------
----------- 4 yes no
- --------------------------------
----------------------------- 5
yes yes 5
--------------------------------------------------
----------- 6 yes no
- --------------------------------
----------------------------- 7
yes no -
--------------------------------------------------
----------- 8 yes no
- --------------------------------
----------------------------- 9
yes no -
--------------------------------------------------
----------- 10 yes
yes 10 -----------------------------
-------------------------------- 11
no
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Contrasting Loops
j 1while(jlt5) System.out.println(Hello)
j j 1
for(int j1 jlt5 jj1) System.out.println(
Hello)
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Arithmetic Sequences

• a first term
• d common difference
• n number of terms
• Sequencea, ad, a2d, , a(n-1)d

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Code
outCnt 0 for(int k0 kltn k) if(outCnt
! 5) System.out.printf("5d", a kd)
else System.out.printf("n5d", a kd)
outCnt 0 outCnt
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Alternate Code
outCnt 0 for(int ka kltand kkd)
if(outCnt ! 5) System.out.printf("5d",
k) else System.out.printf("n5d",
k) outCnt 0 outCnt
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do-while Loops

• Bottom-test loop
• Always executesthe body at least once
• Loops until the Test? returns false

statement
Test?
true
false
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do-while Loops
do statementwhile(?)
Bottom-test loop
while(?) statement
Top-test loop
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Example
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Premature Loop Exit

• break
• Used to exit an enclosing loop statement
• Used to exit a switch statement

x keyBoard.nextInt()while(xlt100)
System.out.println(x) if(x 4 0)
break x x 7
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switch Statement

• Used in place of a series of if-else if-else ifs
• When the test produces an integer value

if(month1) else if(month2)
switch(month) case 1 break
case 2 case 3 break
default