Programming 1

Nested loops

Objective

• control of loop using

✓ Break statement

✓ Continue statement

• Nested loop

Concept of loop

• Loop is the execution of a number of commands as a block

based on a certain condition a number of times.

• It is called Loop because the flow of operations is repeated in

loop.

Example of loop statements

• Write a program that prints the factorial of even numbers from 2 to 10

You could exit the loop before the condition becomes false???

• Usually the only way out of programming statements is to finish evaluating the condition with a false value.

• However, it is often best to terminate the programming statements when certain conditions are met, to save time of processor.

You could exit the loop before the condition becomes false???

• In Java that by use:

✓ Break statement

✓ Continue statement

Break concept

• The break statement is used to force the compiler to exit even and If the number of iterations is not already assigned.

• The compiler then exits to execute the first program command immediately after loop.

• Used in loops or selection statements in general, but use in a switch is mandatory.

• How to write:

break;

Break Example

Break Example

• Output: 0, 1, 2, 3

Break Example

• Write a for program with break statement do the following:

• Read 10 numbers from users.

• Calculate the total number.

• If user enter number 999 then the loop is end and without calculate the number.

Break Example

Break Example

• Do the following:

• Enter 10 numbers from user.

• Calculate the total number

• If user enter 0, end the program and display the result.

Break Example

Continue concept

• The continue statement is used to force the compiler to end the current cycle and start a new cycle by returning to the loop head.

• How to write:

continue;

Continue Example

The execution go to the

condition

Ignore these

statements

This statement out of while loop

Continue with For loop

Continue with For loop

• Output: 0, 1, 2, 3, 5,6,7,8,9

• Where is the 4????

• Because continue statement the loop statement not executed when i =4

Continue with While loop

• Do the following:

• Use while loop to calculate total of numbers between 1 to 99

• If the number is multiples of 10 (10 , 20 , 30 ….) then ignore the current cycle in while loop and not calculate this number.

• Display the result

Continue with While loop

Difference between break and continue

Difference between break and continue

By using the continue

statement, the for loop

will continue to print the

numbers from 1 to 4 and

when the value of the

counter( count = 5 )will

ignore the rest of the

cycle and come to the

beginning of the for loop

resumed from the

number 6 and complete

printing.

Difference between break and continue

With break statement ,

the for loop will

continue to print the

numbers 1 to 4 and when

the value of the counter(

count = 5 ) will be forced

out of for loop.

Break Example

• The program will allow the user to enter 10 numbers and then collect them in case The user enters zero.

Break and Continue Example

• What is the output???

Nested loops

• Loop can contain another loop inside it.

• The internal loop must have a counter variable name different from the variable name counter for external loop.

• Loop inside another loop that creates nested loops.

• The internal loop is performed in each external loop cycle.

Nested loops

• the nested loop can be for, while or do.. while

Nested loops Example

• external For loop repeated 5 times.

• The internal For loop repeated 10 times for each external For loop.

• So the total of cycle in loops is 50 times.

Nested loops Example

• How much cycles in loops???

Nested loops Example

Nested loops Example

Nested loops Example

• What is the result ???

Nested loops Example

• What is the result ???

Nested loops Example

• What is the result ???

Nested loops Example

• What is the result ???

Nested loops Example

• Write program using nested for loop to get the following result ???

Nested loops Example

• Nested loop with more than 2 loops.

Notes

• One of the most common error is to write the counter name error for one of the nested loop.

Notes

• Write commands is a good practice in program.

• Without commands:

✓That make statements is not clear

✓Not easy to understand program.

Notes

// Print numbers(1, 2, 3, 4, 5) 10 times on 10 different lines

//Move between 10 lines

// Print numbers(1, 2, 3, 4, 5)

in the same line.

Summary

• control of loop using

✓ Break statement

✓ Continue statement

• Nested loop