1. while while (condition) { statements }
Can put anything in “statements”
The entire construct is called a while loop
statements are executed until condition is true
Even before executing it the first time condition is evaluated
A while loop may not execute even once

2. Example class justAnExample { public static void main(String arg[]) {
int x = 5;
int y = 0;
while (x < 10) {
y--;
x++; }
System.out.println(y);

3. Example class justAnExample { public static void main(String arg[]) {
int x = 15;
int y = 0;
while (x < 10) {
y--;
x++; }
System.out.println(y);

4. Sum of natural numbers class naturalSum {
public static void main(String arg[]) {
int n = 2;
int y = 1;
while (n <= 100) {
y += n;
n++; }
System.out.println(“Sum of the first ” + (n-1) + “ natural numbers is ” + y);

5. Sum of natural numbers class naturalSumAnotherWay {
public static void main(String arg[]) {
int n = 99;
int m = n+1;
int y = 100;
while (n > 0) {
y += n;
n--; }
System.out.println(“Sum of the first ” + m + “ natural numbers is ” + y)

6. do-while do { statements } while (condition);
“statements” execute at least once irrespective of condition

7. for loops for (expression1; condition; expression2) { statements }
Same as
expression1
while (condition) {
expression2

8. Sum of natural numbers class naturalSum {
public static void main(String arg[]) {
int n;
int y = 1;
for (n=2; n <=100; n++) {
y += n; }
System.out.println(“Sum of the first ” + (n-1) + “ natural numbers is ” + y)

9. Comma operator in for loop
for (expression1a, expression2a, …; condition; expression1b, expression2b,…) {
statements }
Same as
expression1a
expression2a …
while (condition) {
expression1b
expression2b …

10. Sum of natural numbers class naturalSum {
public static void main(String arg[]) {
int n;
int y;
for (n=2, y=1; n <=100; y += n, n++) { }
System.out.println(“Sum of the first ” + (n-1) + “ natural numbers is ” + y) }

11. Empty for loop body for (expression1; condition; expression2) { }
Same as
for (expression1; condition; expression2);

12. Infinite loops Loops that never terminate while (true) { statements }
do {
} while (true);

13. Infinite loops for (expression1; ;expression2) { statements }
for (i=0; i > -10; i++) {
for (i=0; i<=100; i--) {