WARM-UP: MON, APR 7 What are loops used for in programming? What are at least 2 different kinds of loops?

CHAPTER 5: LOOPS PRE-AP COMPUTER SCIENCE CYCLE 6

REVIEW: IF STATEMENTS Used to make decisions/answer questions Formed using a conditional statement Conditional operators IF  IF-ELSE  IF – ELSE-IF – ELSE

IF STRUCTURE if (condition1) { //statements } else if (condition2) { //statements } else { //statements }

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

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

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

WHILE LOOPS - STRUCTURE while (condition) { //statements //counter/environment change }

WHILE LOOPS - STRUCTURE while (condition) { //statements //counter/environment change } Statements – the tasks you want repeated Counter change – prevents infinite loops

EXAMPLE A: PRINT 1 THRU 100 int number = 1; while (number <= 100) { System.out.println(number); number++; }

EXAMPLE B: PRINT 1 THRU AN INPUTTED NUMBER int number = 1; int stop = console.nextInt(); while (number <= stop) { System.out.println(number); number++; }

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++; }

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?

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++;

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 }

EXAMPLE: PRINT 1 THRU AN INPUTTED NUMBER int number = 1; int stop = console.nextInt(); while (number <= stop) { System.out.println(number); number++; }

FOR LOOPS Typically used in looping situations where the number of iterations is known Always counter controlled

FOR LOOPS - STRUCTURE for (start; stop; change) { //statements } Start, stop, change refer to the counter

EXAMPLE A: PRINT THE NUMBERS 1 THRU 100 int counter; for (counter=1; counter<=100; counter++) { System.out.println(counter); }

EXAMPLE B: PRINT THE WORD “HELLO” 5 TIMES int i; for (i=1; i<=5; i++) { System.out.println(“Hello”); }

EXAMPLE C: PRINT OUT ALL EVEN NUMBERS BETWEEN 0 AND 1000 for (int num=0; num<=1000; num=num+2) { System.out.println(num); }

FOR VS WHILE WHILE int i=0; while (i < 100) { System.out.print(i); i++; } FOR for (int i=0; i < 100; i++) { System.out.print(i); }

WARM-UP: APR 10 Write a FOR loop that would loop 25 times with a counter that begins at 12. QUIZ TOMORROW!