CP122 CS I. Chapter 6a: Iteration I

Transcription

1 CP122 CS I Chapter 6a: Iteration I

2 Supreme Court ruling: Samsung's violation of Apple's iphone patents may only involve components and not whole phone Tech News!

3 Tech News! Supreme Court ruling: Samsung's violation of Apple's iphone patents may only involve components and not whole phone Uber update tracks rider's GPS from time of trip request to 5 minutes after drop-off

4 Hckr's Tip of the Day: Robotics!

5 Microprocessor Hckr's Tip of the Day: Robotics! IR Sensors Actuators control movement

6 public class Robot { public boolean detectwall() { if (irvalue < 50) { return true; else { return false; Robot r = new Robot(); if (r.detectwall()) { r.backup(); r.turnright(); else { r.goforward();

7 Chapter 6: Iteration How can we get the computer to repeat blocks of code? How can we make the computer do many things without too much code?

8 A Complicated Program public class SayHello {

9 Rudimentary Spam public class SimpleSpam {

10 Rudimentary Spam public class SimpleSpam { This is ugly!

11 A Spammer's Delight public class PowerfulSpam { public static final int SPAM_AMOUNT = 100; for (int i = 0; i < SPAM_AMOUNT; i++) {

12 A for Spammer's is a Java keyword. Delight It starts a loop (repeated block of code) public class PowerfulSpam { public static final int SPAM_AMOUNT = 100; for (int i = 0; i < SPAM_AMOUNT; i++) {

13 A Spammer's Delight public class PowerfulSpam { This is the loop initialization. A counting variable, i, is defined and initialized to 0. public static final int SPAM_AMOUNT = 100; for (int i = 0; i < SPAM_AMOUNT; i++) {

14 A Spammer's Delight public class PowerfulSpam { This is the loop ending condition. The loop continues until this condition becomes false. public static final int SPAM_AMOUNT = 100; for (int i = 0; i < SPAM_AMOUNT; i++) {

15 A This Spammer's is the loop update. Delight i's value is updated at the end of each loop iteration. public class PowerfulSpam { public static final int SPAM_AMOUNT = 100; for (int i = 0; i < SPAM_AMOUNT; i++) {

16 A Spammer's Delight public class PowerfulSpam { Everything inside these curly braces is the body of the loop. public static final int SPAM_AMOUNT = 100; for (int i = 0; i < SPAM_AMOUNT; i++) {

17 A Spammer's Delight public class PowerfulSpam { This loop consists of a single repeated statement: a println. public static final int SPAM_AMOUNT = 100; for (int i = 0; i < SPAM_AMOUNT; i++) {

18 HelloSpammer.java

19 Use the loop variable public class Counter { for (int i = 0; i < 10; i++) { System.out.println( Counter: + i);

20 Go backwards public class Counter { for (int i = 10; i > 0; i--) { System.out.println( Counter: + i);

21 Count by 3 public class Counter { for (int i = 0; i < 100; i += 3) { System.out.println( Counter: + i);

22 Challenge! Write a loop that sums up the numbers 1 to 100

23 Another kind of loop: while int i = 0; while (i < 10) { System.out.println( Counter: + i); i++;

24 Sum consecutive integers until reaching 50 int i = 1; int sum = 0; while (sum < 50) { sum += i; i++; System.out.println( The last number added was + i);

25 public class Counter { Challenge! Convert the FOR loop below into a WHILE loop that does the exact same thing. for (int i = 0; i < 100; i += 3) { System.out.println( Counter: + i);

26 A Tricky Error int i = 0; while (i < 10) { System.out.println( Counter: + i);

27 Another Tricky Error int i = 0; while (i < 10); { System.out.println( Counter: + i); i++;

28 A Robot Invasion! Let's add a loop to Robot.java that makes 100 Robot objects and adds them to the screen!