1. Karel J Robot
Chapter 6

2. What we have learned so far:
Classes vs objects (e.g. UrRobot vs. karel)
Parts of a class (constructor, method)
Classifying errors
Polymorphism (extending classes)
Abstract classes and interfaces
Conditionals
Booleans, logical operators

3. For Loop
Loops – code that repeats some action either a finite or infinite amount of times
Also called iteratives
2 types of loops
Definate loops (for) perform instructions an explicit number of times
Indefinate loops (while) perform instructions until a certain test fails

4. For Loop Example: public void move(int numMoves){..}
Which loop do we want?
Structure of a for loop:
For(int x = 0; x<10; x++)
{ <repeated code>}
For loop needs 3 things:
An initializer – can be initialized in for loop, or before
A boolean test – loop while run until the test is false
An operation – typically an incrementer

5. For Loop How many times will each for-loop run?
for(x=0; x<10; x++) { …}
for(x=0; x<=10; x++){…}
for(x=10; x>0; x--){…}
for(x=2; x>=14; x+=2) {…}
Feel free to program the code and test it
Let’s keep to a standard form:
Start: x=0;
Test: x<#; //don’t use <=; the # will represent how many times the loop runs
Increment by x++;

6. While Loop
Aside: the For-Loop takes on different forms, but the previous slides demonstrate its simplest form
For Loop – good for looping when you know how many times you need to repeat
When you need to program a loop that runs until a certain event happens…. Use a while loop

7. While Loop Form: while(<test>) { <do instructions>}
Examples:
while(!nextToABeeper()) {..}
while(x>10){…}
while(2>=4){…}
The test can be any boolean outcome
The actions in the loop should make progress to change the boolean test (to avoid an infinite loop)

8. Relational Operators Review ->Logical operators: &&, ||, !
Relational Operators are used for comparison
>, >=, < <=, ==, !=
Note: = and == are not the same thing! = is the assignment operator… == is ‘equal to’

9. Student work Read chapter 6 (up to page 161)
Program the Guard robot on page 162 to the end of the chapter
Problem set 6
#1,2,3,8,14,16,24,34