1. Lab5 PROGRAMMING 1
Loop chapter4

2. BEFORE WE START Your Cell Phone Silent Please Keep Quite
Find Your Computer and Switch On
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3. content . Loops & Selection Statements. introduction to Loop
While, Do-while and For .
Differences between While, Do-while and for .
To implement program control with break and continue .
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4. Loop &&selection statement
Selection statements, like if…else, allow for conditional execution of code blocks in a single iteration
Loops are structures that control repeated execution of the same block of statements
code block
if…else
true
false
loop?
code block
true
false
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5. Introduction to Loop Loop consist of :
Body of the loop : the code which want to do more than one time
Control statement (conditions ): A Boolean expression controls the execution of the body of the loop
Execute the loop again if true
Terminate the loop if false
False
Two kind of loops:
Body of the loop
Condition
True
Finite loop
The statement in the body will executed number of times, from zero to finite number
Infinite loop
A loop that’s continuo forever
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6. Loop control structure
Entry control loop
Exit control loop
The control conditions are tested before the start of the loop execution.
If the conditions are not satisfied , then the body of the loop will not be executed.
The Test is performed at the end of the body of the loop and there fore the body is executed unconditionally for the first time.
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7. The while Loop The syntax for the while loop is as follows: 1
while (loop-continuation-condition) {
// Loop body
Statement(s);
Change; }
initialization ; 2
loop body 3
1-Initialization: the variable tested in the condition must be initialize to some value.
2-condition: the condition that tested before any iteration. If it false, then the program will not enter to loop and continue to the next statement after the loop
3-Change: the variable that tested must be change within the body loop.
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8. The While loop }// end while int Number = 10;
while ( Number >= 0 ) {
System.out.println( "Number is " + Number );
Number--;
}// end while
System.out.println( "Loop ended");
Initialize the number to 10 .
Test whether "Number >= 0".
If it is FALSE, end the loop, and continue with the statements after the loop. In this case, the next statement to be executed would print out the "Loop ended" message.
If the result of "Number >= 0" is TRUE, execute the statements in the body of the loop (in this case first print a message, and then decrement the value of "Number" by 1 ), and then return to step (ii) above.
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9. Total 55 Exercise 1 What is the output of the following code segment?
int Counter = 0, total=0;
while (Counter<=10) {
Total += Counter;
Counter++;
} // end while
System.out.println( "Total " + T);
Total 55
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10. The do-while Loop The do-while loop is a variation of the while loop.
Its syntax is given below:
1-Initialization: the variable tested in the condition must be initialize to some value.
2-Change: the variable that tested must be change within the body loop.
3-Condition: the condition that tested After the first iteration. If it false, then the program will not enter to loop and continue to the next statement after the loop. 1
do {
// Loop body;
Statement(s);
Change;
} while (loop-continuation-condition);
initialization ; 2 3
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11. The do-while Loop int i = 0; do { System.out.println(i); i++;
} while ( i < 10 );
System.out.println(“Loop ended”);
Initialize the i to 1 .
Print the i and increment by 1
Test whether “i<10".
If it is FALSE, end the loop, and continue with the statements after the loop. In this case, the next statement to be executed would print out the "Loop ended" message.
If the result of “i<10" is TRUE, return to step (ii) above.
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12. Exercise 2
Exercise 2
What is the output of the following code segment?
int Counter = 10, i=2;
do{
System.out.println( (i*i) );
Counter++;
i++;
} while (Counter<=10);// end while
System.out.println( "End"); 4
End
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13. The for Loop In general, the syntax of a for loop is shown as below:
for ( initialization; condition ; Change ) {
statements; } 2 3 1
1-Initialization: is used to initialize variables used in the loop and is run only once at the start.
2-Condition: The Boolean expression is checked before each iteration. If it is false the loop will terminate.
3-Change: The increment/decrement of the loop control variable and is run after each successful iteration(after executed the body)
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14. Exercise 3
What is the output of the following code segment?
for ( int Count = 0; Count < 10; Count++ ) {
System.out.print(Count+" "); }
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15. Differences between While, Do-while and For
for (initialization ; condition; Change) {
// loop body
statement(s); }
While
Initialization;
while (condition) {
// loop body
statement(s);
Change; }
Do-While
Initialization;
do {
// loop body
statement(s);
Change;
} while (condition);
Use when number of repetitions is not known
Use when loop body must be executed at least once and number of repetitions is not known
Use when number of repetitions is known (print 100 times
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16. Break Statement Or used in for, while, do-while loop,
The break statement in Java has two forms: labeled and unlabeled
1- Unlabeled break
Normally, we knew unlabeled break used in switch-case statement, to break the following execution in the block.
Example: int HOUR = 3; switch(HOUR) { case 1:
break; case 2:
break; case 3: break; case 4: break; default: break; }
Or used in for, while, do-while loop,
for example: for(int i=0; i<10; i++) { System.out.print(i + " "); if(i == 3) break; }
(Which printed: [ ])
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17. Break statement
2- Labeled break
There is another type of break called labeled break. We can use labeled
break to break the following execution and transfer the of control back to
the labeled statement immediately.
Example: int input = 3; validation: { System.out.println("start"); if(input == 4) System.out.println("pass"); if(input < 4) break validation; System.out.println("the input is not equal 4
and not smaller than 4"); if(input > 4) break validation; System.out.println(“end”);
} System.out.println("another end");
It should print: start another end
The program execution will break from
the validation block (declared curly
braces) and jump to the end followed
by the block.
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18. Continue Statement Continue Statement :
Continue statement is used when we want to skip the rest of the statement
in the body of the loop and continue with the next iteration of the loop. There are two forms of continue statement in Java:
1. Unlabeled Continue Statement 2. Labeled Continue Statement
1. Unlabeled Continue Statement
This form of statement causes skips the current iteration of innermost for,
while or do while loop.
Example:
for(int var1 =0; var1 < 5 ; var1++)
        for(int var2=0 ; var2 < 5 ; var2++)
        {
                if(var2 == 2)
                        continue;
                        System.out.println(“var1:” + var1 + “, var2:”+ var2); }
In this example, when var2
becomes2, the rest of the
inner for loop body
will be skipped.
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19. Continue Statement Example: Outer: 2. labeled Continue Statement
Labeled continue statement skips the current iteration of the loop marked
with the specified label. This form is used with nested loops.
Example:
Outer:
for(int var1 =0; var1 < 5 ; var1++) {
        for(int var2=0 ; var2 < 5 ; var2++)
        {
                if(var2 == 2)
                        continue Outer;
System.out.println(“var1:” + var1 + “, var2:”+ var2); } }
In this example, when
var2 becomes 2, rest of the
statements in body of inner
as well outer for loop will be
skipped, and next iteration of
the Outer loop will be executed.
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20. Thank You !