The document discusses while and do-while loops in Java. The while loop evaluates a condition and executes the code block if it is true. It continues checking the condition and executing the block until false. The do-while loop executes the code block first and then evaluates the condition, repeating until false. Both loops are demonstrated with examples that output iterating numbers or running sums.

1. IMPLEMENTING WHILE AND DO
WHILE LOOP
Chapter 5.1:

2. Repetition Statements
 Repetition statement (or loop) a block of code to
be executed for a fixed number of times or until a
certain condition is met.
 In JAVA, repetition can be done by using the
following repetition statements:
a) while
b) do…while
c) for

3. The while statement
 The while statement evaluates
expression/condition, which must return a
boolean value. If the expression/condition is
true, the statement(s) in the while block
is/are executed.
 Syntax:
while (expression/condition)
Statement(s);
 It continues testing the expression/condition
and executing its block until the
expression/condition evaluates to false

4. The while statement

5. Example 1
Output ? 1 2 3 4
int i=1;
while (i<5){
System.out.print(i + “”);
i++;
}

6. Example 2
Output ? SUM : 1
SUM : 7
Good Bye
int sum=0, number =1;
while (number <= 10)
{
sum+=number;
number = number + 5;
System.out.println(“SUM :” + sum);
}
System.out.println(“Good Bye”);

7. The do…while statement
 It is similar to while loops except it first executes
the statement(s) inside the loop, and then
evaluates the expression/condition. If the
expression is true, the statement(s) in the do loop
is/are executed again.
 Syntax
do
statement(s);
while (expression);
 It continues executing the statement until the
expression/condition becomes false.
 Note that the statement within the do loop is
always executed at least once.

8. The do…while statement

9. Example 3
Output ? 0 1 2 3
int i=0;
do{
System.out.print(i + “”);
i++;
}while(i<=3);

10. Example 4
Output ? SUM : 2
SUM : 9
int sum=0, number =2;
do{
sum+=number;
number = number + 5;
System.out.println(“SUM :” + sum);
} while (number <= 10);