1. Control Structures

2. Sequential Execution x = keyBoard.nextInt(); statement statement
y = 2*x - 3;
statement
System.out.println(x); … …
System.out.println(y);
statement

3. Selecting Execution Route?
true
statement
false
if(?){ statement; }

4. Selecting Execution Route?
true
statement _1
false
statement_2
if(?){ statement_1; } else{ statement_2; }

5. for Loops Referred to as the “counting” loop Parts of a for-loop
Initialize counter
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
Update counter

6. for Loops for(initialize; test; update){ body }
for(initialize_variable; test_variable; change_variable) {
//body of loop goes here }

7. while loop

8. //display all divisors of a given 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

9. while d less than or equal to N{ if(d divides evenly into N){ print d
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 <= N? d divdes N? output
==============================================================
yes yes
yes yes
yes no
yes no
yes yes
yes no
yes no
yes no
yes no
yes yes no

10. Contrasting Loops
j = 1; while(j<=5){ System.out.println(“Hello”); j = j + 1; }
Remember to update j
for(int j=1; j<=5; j=j+1){ System.out.println(“Hello”); }

11. Arithmetic Sequences a = first term d = common difference
n = number of terms
Sequence: a, a+d, a+2d, …, a+(n-1)d

12. Code outCnt = 0; for(int k=0; k<n; k++){ if(outCnt != 5)
System.out.printf("%5d", a + k*d);
else{
System.out.printf("%n%5d", a + k*d); }
outCnt++;

13. Alternate Code outCnt = 0; for(int k=a; k<a+n*d; k=k+d){
if(outCnt != 5)
System.out.printf("%5d", k);
else{
System.out.printf("%n%5d", k); }
outCnt++;

14. do-while Loops Bottom-test loop Always executes the body at least once
Loops until the Test? returns false
statement
Test?
true
false

15. do-while Loops do{ statement; }while(?); while(?){ statement; }
Bottom-test loop
while(?){ statement; }
Top-test loop

16. Example

17. Premature Loop Exit break Used to exit an enclosing loop statement
Used to exit a switch statement
x = keyBoard.nextInt(); while(x<=100){ System.out.println(x); if(x % 4 == 0) break; x = x + 7; }

18. switch Statement Used in place of a series of if-else if-else ifs
When the test produces an integer value
if(month==1){ … } else if(month==2){ … } …
switch(month){ case 1: … break; case 2: … case 3: … break; … default: }