1. Perfect squares class identifySquareButLessClever {
public static void main (String arg[]) {
int n = 48;
int i;
if (n < 0) {
System.out.println (n + “ is not a perfect square.”); }
else if ((n==0) || (n==1)) {
System.out.println (n + “ is a perfect square.”);
else {
for (i=2; i<=n/2; i++) {
if ((i*i) == n) {
System.out.println(n + “ is square of ” + i);

2. break
In the last example you may want to come out of the for loop as soon as you discover that n is a square
The computation done after this is useless
Use break
Breaks out of the loop (while, do-while, or for) currently you are in
for (i=2; i<=n/2; i++) {
if ((i*i)==n) {
System.out.println(n + “ is square of ” + i);
break; }

3. break Another way to achieve the same effect without using break
class identifySquare{
public static void main (String arg[]) {
int n = 48;
int i;
if (n < 0) {
System.out.println (n + “ is not a perfect square.”); }
else if ((n==0) || (n==1)) {
System.out.println (n + “ is a perfect square.”);
else {
for (i=2; (i<=n/2) && ((i*i) != n); i++) ;
if ((i*i)==n) {
System.out.println(n + “ is square of ” + i);

4. continue
Allows you to skip parts of a for or while or do-while loop statements
Example (want to print two-digit numbers with both digits odd)
for (i=10; i<100; i++) {
if ((i%2)==0) {
continue; }
if (((i/10)%2)==1) {
System.out.println(i + “ has odd digits.”);

5. Perfect numbers class perfectNumber {
public static void main (String arg[]) {
int n = 24;
int d, sigma_n = 1+n;
for (d=2; d<=n/2; d++) {
if ((n%d) != 0) {
continue; }
sigma_n += d;
if (sigma_n == 2*n) {
System.out.println (n + “ is perfect.”);

6. switch-case An alternative of if-else if-…-else switch (expression) {
case constant1: // integer or character
statements1
case constant2:
statements2 …
case constantN:
statementsN
default:
statementsD }

7. switch-case Same as if (expression==constant1) { statements1…
statementsN
statementsD }
else if (expression==constant2) {
statements3
// continued on next slide

8. switch-case else if (expression==constant3) { statements3 statements4…
statementsN
statementsD }
else if (expression==constantN) {
else {

9. switch-case with break
switch (expression) {
case constant1:
statements1
break;
case constant2:
statements2 …
case constantN:
statementsN
default:
statementsD }

10. switch-case with break
Same as
if (expression==constant1) {
statements1 }
else if (expression==constant2) {
statements2 …
else if (expression==constantN) {
statementsN
else {
statementsD

11. switch-case: more flavors
switch (expression) {
case constant1:
case constant2:
statements1
break;
case constant3:
statements3 …
case constantN:
statementsN
default:
statementsD }

12. switch-case: more flavors
Same as
if ((expression==constant1) || (expression==constant2)) {
statements1 }
else if (expression==constant3) {
statements3 …
else if (expression==constantN) {
statementsN
else {
statementsD