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CS 180 Problem Solving and Object Oriented Programming Fall 2011

CS 180 Problem Solving and Object Oriented Programming Fall 2011. http://www.cs.purdue.edu/homes/apm/courses/CS180Fall2011/. Notes for Week 2: August 29-September 2, 2011. Aditya Mathur Department of Computer Science Purdue University West Lafayette, IN, USA.

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CS 180 Problem Solving and Object Oriented Programming Fall 2011

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  1. CS 180 Problem Solving and Object Oriented Programming Fall 2011 http://www.cs.purdue.edu/homes/apm/courses/CS180Fall2011/ Notes for Week 2: August 29-September 2, 2011 Aditya Mathur Department of Computer Science Purdue University West Lafayette, IN, USA

  2. Readings and Self-help Exercises for Week 2 Readings: Chapter 2: 2.1, 2.2, 2.3, 2.4 Self help exercises (not to be turned in): 2.1, 2.2, 2.3, 2.4, 2.7, 2.9, 2.12, 2.14 CS 180. Fall 2011. Week 2

  3. About Homework All homework problems will be assigned during recitation. Please make sure you attend your recitation section. Homework assigned during week X is due at the start of your recitation during week X+1. It is best to use Piazza to ask questions regarding homework. But please do not post answers to homework problems. Most, but not necessarily all, homework problems will be from the textbook. CS 180. Fall 2011. Week 2

  4. Lab for Week 2 Play with Java programs: Introduction to Android-based smart phone Introduction to the Finch robot CS 180. Fall 2011. Week 2

  5. Feedback for Week 1 CS 180. Fall 2011. Week 2

  6. Q1. I understand the difference between “sequential solution” and “Concurrent solution”. Yes No (c) Not sure (d) Missed week 1 lecture (s) CS 180. Fall 2011. Week 2

  7. Q2. I understand the difference between “Data Parallelism” and “Task parallelism”. Yes No (c) Not sure (d) Missed week 1 lecture(s) CS 180. Fall 2011. Week 2

  8. Dissecting a Java Program: Preliminaries CS 180. Fall 2011. Week 2

  9. The edit, compile, execute cycle .java file(s) .class file(s) (byte code) Correct program No syntax error Edit a Java program Compile your program Execute your program Syntax Error Run time Error or Incorrect Output In CS 180 we shall use DrJava for editing, compiling and execution. DrJava is an Integrated Development Environment also known as an IDE. Eclipse, JBuilder, and IntelliJ IDEA are a few other Java IDEs. For programming the RidgeSoft robot we shall use RoboJDE. CS 180. Fall 2011. Week 2

  10. Classes and Objects Represent Create Set of real or virtual objects Template in Java Objects created Class Animal Class Flower Class Car Class Dog Class Student animal momsCar bruschetta ziggy car amanda student flower dog CS 180. Fall 2011. Week 2

  11. Classes and Objects Class: Contains attributes and operations related to some real or virtual object. This object could be abstract or concrete [e.g., a Dog or a Golden Retriever]. Object: Created from a class.Contains specialized properties (attributes) and operations related to a more specific real or virtual object, e.g., object myDog created from class Dog has breed as a property that might be different from another object marysDog created from the same class. CS 180. Fall 2011. Week 2

  12. Java program: Structure Package [Contains one or more classes] Data represents properties of a real, virtual or a Java object. E.g., breed, age, color Class [Data and zero or more methods] Data (attributes) Methods are operations that can be performed on an object created from a class. E.g., run(), sit(), down(), no(), goodBoy() Method Data and statements At least one class must have a method named main(). CS 180. Fall 2011. Week 2

  13. Java program: Classes and Objects class Automobile make model maxSpeed make model maxSpeed Data create camry make model start() start() Method Data and statements create mazdaRX7 Objects derived from Class Automobile CS 180. Fall 2011. Week 2

  14. Elements of a Sequential Java Program For practice (try later): Programs to be dissected: Program 2.6 ScannerExample.javaChapter 2 pages 55-56. Program 2.7 BouncingBall.javain Chapter 2 pages 58-59. Strategy: Go through this program line by line and attempt to understand the meaning of each line. It is likely this exercise will generate more questions than answers. CS 180. Fall 2011. Week 2

  15. Elements of a Concurrent Java Program For practice (try later): Program to be dissected: Program 2.8 AreaMeasuringRobot.java in Chapter 2 pages 63-64. Strategy: Go through this program line by line and attempt to understand the meaning of each line. It is likely this exercise will generate more questions than answers. CS 180. Fall 2011. Week 2

  16. Announcements Feast with faculty tonight: 6:30pm in Ford Dining Hall, room on the second floor. Lab makeup policy at the course web site. This week’s recitation: you will learn about the Scannerclass and how to map a problem to a Java program. Make sure you attend! Project 1 description will be released via the Schedule page of the course site on Sunday (a day before the announced date). Is Java a pure OO language:? Use Google to find an answer. CS 180. Fall 2011. Week 2

  17. Binary numbers and Floating point representation “I hate floating point and IEEE format!!” Knowledge useful in CS 240, CS 314, and several other classes. Writing programs for engine control, satellite control, aircraft design, integration, etc. etc. Understanding why the results of a computation are not what you expected. CS 180. Fall 2011. Week 2

  18. Types Set of values Set of Operations x a x x c b x x CS 180. Fall 2011. Week 2

  19. Primitive types: int, long Set of integers Set of Operations -14 2010 / + 12 * - % 1751 180 Integer.MAX_VALUE: 231 -1 Integer.MIN_VALUE: -231 Long.MAX_VALUE: 263 -1 Long.MIN_VALUE: -263 CS 180. Fall 2011. Week 2

  20. Primitive types: float, double Set of real numbers Set of Operations (sample) 3.14 2010.98135 == + Infinity * >= 12.77 - > -Infinity .2010E4 NaN 180.0 -1751.0 Float.MAX_VALUE: 3.40282347e+38 Float.MIN_VALUE: 1.40239846e-45 Double.MAX_VALUE: 1.79769313486231570e+308 Double.MIN_VALUE: 4.94065645841246544e-324 CS 180. Fall 2011. Week 2

  21. Primitive types: boolean Set of logical values Set of Operations (sample) == true || && | != false CS 180. Fall 2011. Week 2

  22. Primitive types: char Set of characters (sample values shown) Set of Operations (sample) == ‘a’ || && ‘$’ | != ‘&’ ‘+’ CS 180. Fall 2011. Week 2

  23. Operators: Arithmetic, relational, conditional Arithmetic operators + - * / % Relational operators == < > <= >= != Boolean/conditional operators || && a+b*c-d a/b c%d a==b a<=b a!=b a==b||c<d a<=b&&c>d a!=b &&c>d||p+1<q CS 180. Fall 2011. Week 2

  24. Operators: bitwise Bitwise operators &: bitwise AND |: bitwise OR ^: bitwise exclusive OR ~: bitwise complement Bitwise shift operators <<: bitwise left shift >>: bitwise right shift >>>: unsigned right shift a & b: logical and of a and b a|b: logical OR of a and b a <<3: shift bit pattern of a left by 3 bits a>>2: shift bit pattern of a to the right by 2 bits CS 180. Fall 2011. Week 2

  25. Names Used to denote classes, objects, data Contain characters; must start with a letter, or a $ sign or an underscore. Examples: height, area1, Dog, $great Length unlimited, case sensitive. Dog and dog are different names. Convention: All class names begin with an uppercase letter; all other names begin with a lower case letter. CS 180. Fall 2011. Week 2

  26. Constants A constant is something that cannot change during program execution. Examples: Integer constants: 0, 1, -1, +24, 29, 300009998, O14, 0x1B Floating point constants: 0.0, -2.345e28, -0.000976512 Boolean constants: true, false Character constants: ‘ ‘, ‘a’, ‘A’, ‘$’ String constants: “”, “ ”, “Hi!”, “Alice in Wonderland” CS 180. Fall 2011. Week 2

  27. Named Constants A constant can be named and the name used instead of the constant itself. Examples: final float pi=3.14159; final booleandogsExist=true; CS 180. Fall 2011. Week 2

  28. Variables A variable is something whose value may change during program execution. Example: intnumStudents; denotes the number of students whose grads have been processed. Its value changes as each student’s grade is processed by a grade processing program. Every variable has a name and a type. Example: inthurricaneCategory; The name is hurricaneCategory and its type is int. Every variable must be declared before it is used. CS 180. Fall 2011. Week 2

  29. Strings: basics A string is any sequence of Unicode characters You may name a string as in the following: StringmyDogsName; myDogsName is an object of type String. It can take any string as its value. For example, “Max”, “Bently”, “Jake” and “Raja” are possible values of myDogsName. What is the difference between 29 and “29”? CS 180. Fall 2011. Week 2

  30. Strings: assignment You may assign a value to a string object. myDogsName=“Bently”; // Assuming that myDogsName has been declared StringmyCarColor=“Black”; All string objects must be declared before they are used. Thus it would be incorrect to assign a value to myDogsName before it has been declared. CS 180. Fall 2011. Week 2

  31. Strings: Other operations You may apply a variety of operations to strings. Examples follow. String commend=“Bently,”+ “ good girl!; // String catenation StringmyCar=“It’s a Porsche”+ “, and I love it!” +”but maintenance is expensive.” // String catenation StringfirstChar=commend.charAt(0); // Extract character at position 0 CS 180. Fall 2011. Week 2

  32. Strings: More operations There exist a variety of operations on strings. A few are given below. CS 180. Fall 2011. Week 2

  33. Declarations int age; float height, area; String name booleaniAmAlive; intx=1, y=0; StringfirstName=“Harry”; CS 180. Fall 2011. Week 2

  34. Simple expressions Expressions are used to compute “something”. floatx, y, z; // Declare x, y, z as variables of type float x*y+z; // Arithmetic expression, results in float value x<y; // Boolean expression, results in boolean value StringfirstName=“Mary”, lastName= “Jones”; firstName+” “+lastName; // Results in a String More in Chapter 2! And yet more to come! CS 180. Fall 2011. Week 2

  35. Assignment statement An assignment statement allows assigning the value of an expression to a variable. floatp=x*y+z; // p gets the value of x*y+z booleanq=x<y; // q gets the value of x<y StringfirstName=“Mary”, lastName= “Jones”; String name= firstName+” “+lastName; More in Chapter 2! And yet more to come! CS 180. Fall 2011. Week 2

  36. Back to classes and objects CS 180. Fall 2011. Week 2

  37. Creating an object: Mom’s car new Car (“Yellow”, “Mom”, 200); public class Car{ String color=“Yellow”; String owner=“Mom”; int miles=200; String color; String owner; int miles; public intgetMiles(){ } CS 180. Fall 2011. Week 2

  38. Creating an object: Dad’s car new Car (“Black”, “Dad”, 200000); String color=“Black”; String owner=“Dad”; int miles=200000; publicclass Car{ String color; String owner; int miles; public intgetMiles(){ } CS 180. Fall 2011. Week 2

  39. Creating an object: Instance variables publicclass Car{ Instance variables are copied into the new object. Each object has its own values for these variables. String color; String owner; int miles; Thus, two objects of the same type have their own copies of instance variables. public intgetMiles(){ } CS 180. Fall 2011. Week 2

  40. Creating an object: get and set instance variables publicclass Car{ String color; String owner; int miles; Get the value of miles from the object. intdadsCarMIles=dadsCar.getMiles(); public intgetMiles(){ return miles; } public voidsetMiles(int m ){ miles=m; } Set the value of miles in an object. momsCar.setMiles(300); CS 180. Fall 2011. Week 2

  41. Classes and Objects: Summary Class: Template to create objects. Object: Created from a class; may denote a real world or an abstract object; Inherits all instance variables and methods. Instance variables: Variables that become local to an object. get and set methods Used for getting data from and into an object. Constructor Used for creating objects. CS 180. Fall 2011. Week 2

  42. Week 2: August 29-September 2, 2011 Hope you enjoyed this week! Questions? Contact your recitation instructor. Make full use of our office hours. CS 180. Fall 2011. Week 2

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