Warm-up: Mon, apr 7

1. Warm-up: Mon, apr 7 • What are loops used for in programming? • What are at least 2 different kinds of loops?

2. Chapter 5: Loops Pre-AP Computer Science Cycle 6

3. Review: IF Statements • Used to make decisions/answer questions • Formed using a conditional statement • Conditional operators • IF  IF-ELSE  IF – ELSE-IF – ELSE

4. IF Structure • if (condition1) { • //statements • } • else if (condition2) { • //statements • } • else { • //statements • }

5. Loops • Used to repeat tasks • Benefits • Reduce amount of code required • Reduce copy-pasting / repetition • Increase code efficiency (speed) • Makes code more readable / easier to understand

6. Types of loops • WHILE Loops • Tasks with unknown stopping points • “infinite” loops • DO-WHILE Loops • Tasks with unknown stopping points that MUST execute at least once • FOR Loops • Repeat ‘x’ times

7. Types of loops • WHILE Loops • Tasks with unknown stopping points • “infinite” loops • DO-WHILE Loops • Tasks with unknown stopping points that MUST execute at least once • FOR Loops • Repeat ‘x’ times

8. WHILE Loops - Structure • while (condition) • { • //statements • //counter/environment change • }

9. WHILE Loops - Structure • while (condition) • { • //statements • //counter/environment change • } • Statements – the tasks you want repeated • Counter change – prevents infinite loops

10. Example A: Print 1 thru 100 • int number = 1; • while (number <= 100) • { • System.out.println(number); • number++; • }

11. example B: print 1 thru an inputted number • int number = 1; • int stop = console.nextInt(); • while (number <= stop) • { • System.out.println(number); • number++; • }

12. example C: print 10 multiples of an inputted number • int multiple = 1; • int number = console.nextInt(); • while (multiple <= 10) • { • System.out.println(number*multiple); • multiple++; • }

13. Warm-Up: Apr 8 • Write the standard structure for a WHILE loop. • Why is it necessary to change the counter or environment inside of a WHILE loop? What will happen if you do not?

14. Warm-Up: Apr 9 • Correct the following code so that it finds the sum of 10 numbers. • int sum = 0; • while (count < 10) • num = console.nextInt(); • sum = sum + num; • count++;

15. Review: WHILE Loops • Typically used for looping situations where you do not know how many times the loop will iterate • Not always counter-controlled • while (condition) { • //statements • //counter/environment change • }

16. example: print 1 thru an inputted number • int number = 1; • int stop = console.nextInt(); • while (number <= stop) • { • System.out.println(number); • number++; • }

17. FOR Loops • Typically used in looping situations where the number of iterations is known • Always counter controlled

18. FOR Loops - Structure • for (start; stop; change) • { • //statements • } • Start, stop, change refer to the counter

19. Example A: Print the numbers 1 thru 100 • int counter; • for (counter=1; counter<=100; counter++) • { • System.out.println(counter); • }

20. Example B: Print the word “Hello” 5 times • inti; • for (i=1; i<=5; i++) • { • System.out.println(“Hello”); • }

21. Example C: Print out all even numbers between 0 and 1000 • for (intnum=0; num<=1000; num=num+2) • { • System.out.println(num); • }

22. FOR vs WHILE WHILE FOR for (inti=0; i < 100; i++) { System.out.print(i); } • inti=0; • while (i < 100) • { • System.out.print(i); • i++; • }

23. Warm-Up: Apr 10 • Write a FOR loop that would loop 25 times with a counter that begins at 12. • QUIZ TOMORROW!