Loops

1
Loops Do while

• Do While
• Reading for this Lecture, LL, 5.7

2
The do Statement

• A do statement has the following syntax
• The statement is executed once initially, and
  then the condition is evaluated
• The statement is executed repeatedly until the
  condition becomes false

do statement while ( condition )
3
The do Statement

• An example of a do loop
• The body of a do loop executes one or more times
  (Note at least once)
• See ReverseNumber.java (page 244)

int count 0 do count
System.out.println (count) while (count lt 5)
4
The do-while Statement

• public class DoWhileDemo
• //Execution always starts from main
• public static void main(String args)
• System.out.println(Enter a number)
• Scanner keyboard new Scanner(System.in)
• int num keyboard.nextInt()
• int count 0
• do
• count
• System.out.println(count)
• while(count lt num)

do Loop_Body while(Boolean_Expression)
The loop body may be either a single statement or
more likely a compound statement
5
The do-while Statement
Start
do Loop_Body while(Boolean_Expression)
Execute Loop_Body
true
Evaluate Boolean_Expression
false
End loop
6
The do-while Statement
do System.out.print(count ,)
count while(count lt num)
Start
Execute System.out.print(count ,)
count
Evaluate count lt num
true
false
End loop
7
Difference between while and do-while Statements

• Do while
• Do while statement is executed at least once
• Condition is checked after executing statements
  in loop body

• While
• While statement may be executed zero or more
  times
• Condition is checked before executing statements
  in loop body

8
Break in Loops

• The break statement causes execution to break
  out of the repetitive loop execution (goes just
  outside the loops closing )
• The effect of break statement on a loop is
  similar to effect on switch statement.
• The execution of the loop is stopped and the
  statement following the loop is executed.

9
Break in Loops
int count 1 while(count ! 50) count
2 if(count 2 1) break