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Reviewing for the Midterm Covers chapters 1 to 5, 7 to 9

Reviewing for the Midterm Covers chapters 1 to 5, 7 to 9. Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013. Things to Review. Review the Class Slides: Key Things to Take Away – Do you understand these the points? Review Slides, especially if some Key Points are unclear

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Reviewing for the Midterm Covers chapters 1 to 5, 7 to 9

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  1. Reviewing for the MidtermCovers chapters 1 to 5, 7 to 9 Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  2. Things to Review • Review the Class Slides: • Key Things to Take Away – Do you understand these the points? • Review Slides, especially if some Key Points are unclear • Make use of the Textbook • Answer Self-Review Questions at back of each chapter • Select Exercises and Programming Projects to practice • Review Quiz and Assignments • Do you understand how to answer Assignment 3 Written Questions? • Review Quiz #1 and Assignment #2 questions, then see the solutions • Get some Coding Practice! • Sign up on CodingBat.com and work through the problems there

  3. Review the Class Slides • Week 01 • wk01.3 – Background Info, Introduction • Week 02 • wk02.1 – Introduction to Java • wk02.3 – Intro to Objects and String and Scanner Objects • wk02.5 – Packages Enums and Wrappers • Week 03 • wk03.1 – Boolean Expressions, Conditionals, Definite Loops • Week 04 • wk04.1 – Structured Analysis and Data Flow Diagrams • wk04.3 – Review • Week 05 • wk05.1 – Writing Classes • wk05.5 – Quiz 1 Solutions • Week 06 • wk06.1 – Testing • wk06.3 – Arrays • wk06.5 – Inheritance • Week 07 • wk07.3 – Polymorphism

  4. Wk02.1 Slides:Introduction to JavaChapters 1 and 2The Java Language – Section 1.1Data & Expressions – Sections 2.1 – 2.5 Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  5. Ch 1&2 - Key Things to take away: • The print and println methods are two services provided by the System.out object • In Java, the + operator is used both for addition and for string concatenation • An escape character can be used to represent a character that would otherwise cause a compile error • A variable is a name for a memory location used to hold a value of a particular data type • Accessing data leaves them intact in memory, but an assignment statement overwrites old data • One cannot assign a value of one type to a variable of an incompatible type • Constants hold a particular value for the duration of their existence • Java has two types of numeric values: integer and floating point. There are four integer data types and two floating point data types • Java using 16-bit Unicode character set to represent character data • Expressions are combinations of operators and operands used to perform a calculation • The type of result produced by arithmetic division depends on the types of the operands • Java follows a well-defined set of precedence rules that governs the order in which operators will be evaluated in an expression • Narrowing conversions should be avoided because they can lose information

  6. Wk02.3 Slides:Using Classes and ObjectsChapters 3Creating Objects – Section 3.1The String Class – Section 3.2The Scanner Class – Section 2.6 Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  7. Key Things to take away: • Object declarations create place holders which point to an object in memory • The new operator instantiates a new instance of the class • Strings are immutable – changing a string creates a new instance • A variable holds either a primitive type or a reference to an object • Assigning variables of primitive types copies the value • Assigning variables of class types copies a reference to the object • The String class provides useful methods for working with strings • length • concat • substring • toUpperCase • Etc • The System.in object represents the standard input stream • The Scanner Class provides methods for reading input values

  8. Wk02.5 Slides:Using Classes and ObjectsChapters 3Section 3.3 Packages Section 3.4 Random Class Section 3.5 Math ClassSection 3.7 Enumerated Types Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  9. Key Things to take away: • The Java API contains standard set of class definitions • Class definitions can be reused by importing packages • Packages exist for creating random numbers, math, and formatting • You can create your own set of libraries as a package • Java provides wrapper classes for primitive data types so they can be used just like any other object

  10. Wk03.1 SlidesConditionals and LoopsChapter 4 Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  11. Key Things to take away: • Flow of Control determines which statements get executed • Expressions can form complex conditions using logical operators • AND and OR evaluation are short-circuited in Java • Selection statements chose different execution paths based on conditions • If <condition> then <statement>; • If <condition> then <statement1> else <statement2>; • Switch <integer value> {Case 1, Case 2, … Case N} • Java supports two styles of Indefinite Loops: • While <condition> <statement>; • Do <statement> while <condition>; • Java suports two styles of definite Loops: • for ( initialization ; condition ; increment ) <statement>; • For-each using Iterators

  12. Wk04.1 - Wk05.5 Slides:Writing ClassesChapter 5 Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  13. Key Things to take away: • Class and Method Design • Data Flow Diagrams help get a design started • Problem Specification: Nouns become Classes, Verbs become Methods • Decompose methods that get too complex • Class and Method Coding • Methods and Variables have Scope – where they can be seen • Public Scope allows access by users of the Class • Private Scope used to encapsulate data and internal helper methods • Invoking a method copies the actual parameters into the formal parameters • Object Parameters contain references to the actual object and can be modified • Testing • Methodical Testing is important step, every program has bugs • Testing can be black box (functional) or white box (implementation) • Four types of tests: Unit, Integration, System, Regression • Println’s and the Eclipse Debugger are essential tools for debugging

  14. Wk04.3 Slides:ReviewChapters 1 to 4 Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  15. Key Things to take away: • Flow of Control determines which statements get executed • Expressions can form complex conditions using logical operators • AND and OR evaluation are short-circuited in Java • Selection statements chose different execution paths based on conditions • If <condition> then <statement>; • If <condition> then <statement1> else <statement2>; • Switch <integer value> {Case 1, Case 2, … Case N} • Java supports two styles of Indefinite Loops: • While <condition> <statement>; • Do <statement> while <condition>; • Java suports two styles of definite Loops: • for ( initialization ; condition ; increment ) <statement>; • For-each using Iterators

  16. Wk05.5 Slides:Quiz #1Solutions Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  17. Question 3 • Work out the logic one step at a time: • True when A is false => !A • Either B or C are true => B || C • AND => both the above must be true • => !A && B || C But remember to check precedence! • => !A && B || C is evaluated as • =>(!A && B)|| C That’s not right! Need to add parenthesis • => !A && (B || C) !A && (B || C) Validate using a Truth Table:

  18. Question 4 • For full marks, • Do not go through the loop 9 times, execute the loop 5 times • Realize that you can increment counter by 2 within the loop, not by 1 twice • Declare the loop variable within the for loop • If you do not remember HOW to write a Java for loop… • Use Appendix J – it was attached at the back! for (int i=1; i <= 9; i += 2) { System.out.println(i); }

  19. Question 5 • Follow the flow of control: • (Sum > MAX) is true since (100 > 10) • So must call Print1, not Print2 • No {} around else, Print3 not part of the if • So Print3 must get printed as well • Print3 is not doing addition, so not 110 • Print3 doing String Concatenation • So will print “100”+”10” => “10010” x x x x √ x

  20. Wk06.3 Slides:Arrays Chapter 7 Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  21. Key Things to take away: • Arrays are an ordered collection on Array Elements • Array Elements may be Primitive Data Types, or Objects • Arrays are objects • Arrays cannot be extended once created • Command Line Parameters are passed as an Array of Strings • Variable Length Parameter lists passed as an Array of Objects • Array Elements may be other Arrays • Arrays may be one, two, or multidimensional

  22. Wk06.5 Slides:Inheritance Chapter 8 Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  23. Key Things to take away: • Inheritance • Inheritance is the process of deriving a new class from an existing class • Inheritance allows software reuse of existing software • Inheritance creates an IS-A relationship between parent and child classes • Protected visibility provides encapsulation and allows inheritance • A parents constructor can and should by invoked by the child via super • A child class can override a parents methods by redefining them • A child of one class can be the parent of another • All Java classes are derived from the Object class • An Abstract class cannot be instantiated, it represents a concept • Abstract classes must be declared in the child before it can be instantiated • Private members of a class and not be seen directly in the child class • The final modifier can be used to restrict inheritance

  24. Wk07.3 Slides:Polymorphism Chapter 9 Instructor: Scott Kristjanson CMPT 125/125 SFU Burnaby, Fall 2013

  25. Key Things to take away: • Polymorphism • The term polymorphism literally means “having many forms” • A polymorphic reference is a variable that can refer to different types of objects at different points in time • The method invoked through a polymorphic reference can change from one invocation to the next • It is the type of the object being referenced, not the reference type, that determines which method is invoked • Interfaces allow true encapsulation and hide implementation details • Interfaces are critical for supporting GUIs and other functions cleanly

  26. Review the Quiz Solutions and Assignments • Try to do the Quiz again • It should be now be much easier now. See how long it takes you. • Review the solutions and compare to your answers. • Look at the kind of problems – midterm will be similar • Assignments 2 and 3: • Review the questions – midterm will be similar • There will be programming questions

  27. Review Assignment 2 Solutions • Part A – Written Question Solutions • a2WriteUp • Operator Precedence • Generating Random Numbers • Definite Loops • Indefinite Loops • Part B – Programming Solutions • RandomAvg.java • AvgNums.java • Distance.java • MoneyChanger.java • MoneyCounter.java

  28. Review Assignment 3 Questions • Review the Parts A and B Written Questions • Work on the Written Questions (Part A is due Monday in Lab). • Review Part C Programming Problems • Try to solve questions 1 to 4 before the Midterm Exam if you can

  29. Practice your Programming Skills • Sign up to CodingBat.com and work through the examples. • It will give you immediate feedback and track your progress. • Be sure that you know how to: • write boolean expressions and if-then-else conditions • know how to concatenate, compare, and manipulate Strings • write for, while, and do loops • index into arrays, pass arrays as parameters, 1 and 2 dimensions

  30. Key things you should know for the midterm: • You should be able to: • Understand flow of control and the importance of braces • Describe the various phases of software testing • Write boolean expressions using correct operator precedence • Write programs using if-then-else, for, while, do, switch • know how to concatenate, compare, and manipulate Strings • Understand how Primitive Data and Objects parameters work • Work with Arrays and indexing of Arrays, arrays of objects • Explain elements of good design including coupling and cohesion • Be able to create a data flow diagram based on a problem description • Understand the principles of inheritance and polymorphism • Understand how dynamic-binding of methods enables polymorphism • Describe what an Abstract class is • Describe what an Interface is used for • Understand the function of modifiers public, private, static, and final • Be able to use the super and this keywords within methods

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