SWC test question #01. Using objects part I

Transcription

1 SWC test question #01 Using objects part I

2 Using objects part I Give a presentation of the concept objects, and how you use objects You could describe Types Variables Variable definitions The assignment operator Objects and Classes Method definitions Method parameters Return values Material: Objects First with Java, chapter 1, 2 You can refer to the attached code example during the test, if you wish.

3 Using objects part I public class BankAccount private double balance; public BankAccount() balance = 0; public void deposit(double amount) balance = balance + amount; public void withdraw(double amount) balance = balance - amount; public double getbalance() return balance;

4 Using objects part I public class BankAccountTester public BankAccountTester() public void runtest() BankAccount myaccount = new BankAccount(); myaccount.deposit(1000.0); myaccount.withdraw(500.0); myaccount.withdraw(400.0); System.out.println("Expected result is 100.0"); System.out.print("Actual result is "); System.out.println(myAccount.getBalance());

5 SWC test question #02 Using objects part II

6 Using objects part II Give a presentation of the concept objects, and how you use objects You could describe Objects and Classes Method definitions Method parameters Return values Method categories (accessors and mutators) Constructors Object construction Object references Material: Objects First with Java, chapter 1, 2, 3 You can refer to the attached code example during the test, if you wish.

7 Using objects part II public class Employee private String name; private double salary; public Employee(String aname, double asalary) name = aname; salary = asalary; public String getname() return name; public double getsalary() return salary; public void increasesalary(double bypercent) salary = (1 + bypercent/100.0)*salary;

8 Using objects part II public class EmployeeTester public EmployeeTester() public void runtest() Employee john = new Employee("John", 20000); System.out.println("Expected result: John "); System.out.print("Actual result: "); System.out.print(john.getName()); System.out.print(" "); System.out.println(john.getSalary()); john.increasesalary(30); System.out.println("Expected result: John "); System.out.print("Actual result: "); System.out.print(john.getName()); System.out.print(" "); System.out.println(john.getSalary());

9 SWC test question #03 Class Definitions part I

10 Class Definitions part I Give a presentation of the concept classes, and how you implement a class You could describe Encapsulation and abstraction Public interface Constructors Method definition (parameters, return types) Instance fields Access keyword (public and private) Using comments Material: Objects First with Java, chapter 2, 3 You can refer to the attached code example during the test, if you wish.

11 Class Definitions part I /** * Simulates a very simple bank account Per */ public class BankAccount private double balance; /** * Constructs a bank account with an initial balance of zero */ public BankAccount() balance = 0; /** * Deposits amount, i.e. increases balance by amount amount The actual amount */ public void deposit(double amount) balance = balance + amount; ( continues )

12 Class Definitions part I ( continued ) /** * Withdraws amount, i.e. decreases balance by amount amount The actual amount */ public void withdraw(double amount) balance = balance - amount; /** * Gets the current balance The current balance */ public double getbalance() return balance;

13 SWC test question #04 Class Definitions part II

14 Class Definitions part II Give a presentation of the concept classes, and how you implement a class You could describe Public interface Constructors Method definition (parameters, return types) Instance fields Access keyword (public and private) Implementing constructors and methods Categories of variables (instance fields, parameters, local variables) Lifetime of variables Method parameters The this keyword Material: Objects First with Java, chapter 2, 3 You can refer to the attached code example during the test, if you wish.

15 Class Definitions part II public class Employee private String name; private double salary; /** * Creates a new Employee record aname Employee name asalary Initial employee salary */ public Employee(String aname, double asalary) this.name = aname; this.salary = asalary; /** * Returns the employee name Employee name */ public String getname() return name; ( continues )

16 Class Definitions part II ( continued ) /** * Returns the employee salary Employee salary */ public double getsalary() return salary; /** * Increase salary by the given percentage bypercent Salary increase in percent */ public void increasesalary(double bypercent) double newsalary = (1 + bypercent/100)*salary; salary = newsalary;

17 SWC test question #05 Data Types

18 Data Types Give a presentation of data types. You could describe Number types (size, representation) Constants (purpose, definition) Assignment Increment and Decrement Strings Primitive types vs object types Casting, Type conversions Material: Objects First with Java, chapter 1, 2, 3 You can refer to the attached code example during the test, if you wish.

19 Data Types public class MilitaryTime private int timeinmins; public MilitaryTime(String timestr) String hourstr = timestr.substring(0,2); String minstr = timestr.substring(2,4); timeinmins = Integer.parseInt(hourStr)*60 + Integer.parseInt(minStr); public int gettimeinminutes() return timeinmins;

20 Data Types public class MilitaryTimeDiff private MilitaryTime timestart; private MilitaryTime timeend; private final int minsinhour = 60; private final int minsinday = 1440; public MilitaryTimeDiff(String start, String end) timestart = new MilitaryTime(start); timeend = new MilitaryTime(end); (continues )

21 Data Types (continued ) public int getdiffhours() return (getdiffinmins() / minsinhour); public int getdiffmins() return (getdiffinmins() % minsinhour); private int getdiffinmins() int diff = timeend.gettimeinminutes() - timestart.gettimeinminutes(); diff = (diff + minsinday) % minsinday; return diff;

22 SWC test question #06 Collections

23 Collections Give a presentation of collections, with primary focus on the ArrayList class. You could describe General purpose of collections ArrayList definition Accessing elements in an ArrayList ArrayList methods (add, get, remove, size, ) Arrays and loops Comparison with array structure Material: Objects First with Java, chapter 4 You can refer to the attached code example during the test, if you wish.

24 Collections public class AlternateSum private ArrayList<Integer> numbers; public AlternateSum() numbers = new ArrayList<Integer>(); public void findalternatingsum() getnumbersfromuser(); int sum = calculatealternatingsum(); JOptionPane.showMessageDialog(null, Sum is " + sum); ( continues )

25 Collections ( continued ) private void getnumbersfromuser() boolean done = false; while (!done) String input = JOptionPane.showInputDialog( Enter numbers "); if (input.equalsignorecase("q")) done = true; else numbers.add(integer.parseint(input)); ( continues )

26 Collections ( continued ) private int calculatealternatingsum() int altsum = 0; for (int index = 0; index < numbers.size(); index++) if ((index % 2) == 0) altsum = altsum + numbers.get(index); else altsum = altsum - numbers.get(index); return altsum;

27 SWC test question #07 Conditional Statements

28 Conditional Statements Give a presentation of conditional statements (the if statement) in Java. You could describe if statement structure if statement and flowcharts Formulation of conditions, logical operators Comparison of values, simple types Comparison of values, objects if/else statement Multiple alternatives Comparison with loop statements Material: Objects First with Java, chapter 2, 3 You can refer to the attached code example and diagrams during the test, if you wish.

29 Conditional Statements

30 Conditional Statements

31 Conditional Statements public class PayCheck public final double overtimehourlimit = 40.0; public final double overtimewagesrate = 1.5; public PayCheck() public double computethepay(double hourlywages, double hoursworked) double totalpay = 0.0; if (hoursworked > overtimehourlimit) double normalpay = hourlywages*overtimehourlimit; double overtimehours = hoursworked - overtimehourlimit; double overtimehourlywages = hourlywages * overtimewagesrate; double overtimepay = overtimehours * overtimehourlywages; totalpay = normalpay + overtimepay; else totalpay = hourlywages * hoursworked; return totalpay;

32 SWC test question #08 Loop Statements

33 Loop Statements Give a presentation of loop statements (while- and for- loops). You could describe while loop structure while loop flowchart for loop structure Infinite loops Conditions, logical operators The for-each loop Comparison of loop statement types (when to use which type) Material: Objects First with Java, chapter 4 You can refer to the attached code example and diagrams during the test, if you wish.

34 Loop Statements

35 Loop Statements public class CurrencyConverter private boolean userquits; public void convert() userquits = false; double rate = getexchangerate(); while (!userquits) String userinput = getuserinput(); userquits = userinput.equals("q"); if (!userquits) double dollaramount = Double.parseDouble(userInput); double euroamount = dollaramount / rate; presentresult(euroamount); ( continues )

36 Loop Statements ( continued ) private double getexchangerate() String ratestr = JOptionPane.showInputDialog("Enter $-euro exchange rate : "); return (Double.parseDouble(rateStr)); private String getuserinput() return JOptionPane.showInputDialog("Enter dollar amount (or Q to quit) : "); private void presentresult(double euroamount) JOptionPane.showMessageDialog(null, "Amount in euro : " + euroamount);

37 SWC test question #09 Testing

38 Testing Give a presentation of testing topics. You could describe Syntax errors Logical errors Positive and negative testing Regression testing Unit testing and test automation Manual walkthroughs Print statements Debuggers Material: Objects First with Java, Chapter 6 You can refer to the attached code example during the test, if you wish.

39 Testing public class BankAccount private double balance; public BankAccount() balance = 0; public void deposit(double amount) balance = balance + amount; public void withdraw(double amount) balance = balance - amount; public double getbalance() return balance;

40 Testing public class BankAccountTester public BankAccountTester() public void runtest() BankAccount myaccount = new BankAccount(); myaccount.deposit(1000.0); myaccount.withdraw(500.0); myaccount.withdraw(400.0); System.out.println("Expected result is 100.0"); System.out.print("Actual result is "); System.out.println(myAccount.getBalance());

41 SWC test question #10 Inheritance part I

42 Inheritance Part I Give a presentation of inheritance. You could describe Purpose of inheritance Syntax in Java for inheritance Superclasses and subclasses Access rights Initialisation in subclasses Polymorphic variables Type conversion and casting Interfaces and abstract classes Material: Big Java, chapter 8, 9 You can refer to the attached code example during the test, if you wish.

43 Inheritance Part I public class Employee private String name; private double salary; public Employee(String name, double salary) this.name = name; this.salary = salary; public String getname() return name; public double getsalary() return salary;

44 Inheritance Part I public class TemporaryEmployee extends Employee private int monthstobeemployed; public TemporaryEmployee(String name, double salary, int monthstobeemployed) super(name, salary); this.monthstobeemployed = monthstobeemployed; public String getmonthstobeemployed() return monthstobeemployed;

45 Inheritance Part I public class TestEmployee public void runtest() Employee e = new Employee( Jim, ); TemporaryEmployee te = new TemporaryEmployee( Sandy, ,6); Employee ve = e; // OK? TemporaryEmployee tve = e; // OK? ve = te; // OK? tve = te; // OK?

46 SWC test question #11 Inheritance part II

47 Inheritance Part II Give a presentation of inheritance. You could describe Purpose of inheritance Superclasses and subclasses Static types and dynamic types Method overriding and method polymorphism Dynamic method lookup Calling superclass methods in subclasses Abstract methods and abstract classes Interfaces Material: Big Java, chapter 8, 9 You can refer to the attached code example during the test, if you wish.

48 Inheritance Part II public class Employee private String name; private double salary; public Employee(String name, double salary) this.name = name; this.salary = salary; public String getname() return name; public double getsalary() return salary;

49 Inheritance Part II public class Manager extends Employee private double monthlybonus; public Manager(String name, double salary, double monthlybonus) super(name, salary); this.monthlybonus = monthlybonus; public double getsalary() return (super.getsalary() + monthlybonus);

50 Inheritance Part II public class TestEmployee public void runtest() Employee e = new Employee( Jim, ); Manager m = new Manager( Jacob, ,5000.0); System.out.println(e.getSalary()); System.out.println(m.getSalary()); Employee ev = m; System.out.println(ev.getSalary());

51 SWC test question #12 Graphical User Interface

52 Graphical User Interface Give a presentation of graphical user interfaces (GUI). You could describe Separation of GUI and logic GUI libraries in Java GUI components GUI layout and layout managers Frames, panels and containers Event-based applications Event handling Material: Big Java, chapter , 17 You can refer to the attached code example during the test, if you wish.

53 Graphical User Interface public class SomeControls private JFrame frame; public SomeControls() createcontrols(); private void createcontrols() frame = new JFrame("Some Controls"); JPanel mainpanel = new JPanel(); mainpanel.setlayout(new FlowLayout()); JButton but1 = new JButton("One"); mainpanel.add(but1); JButton but2 = new JButton("Two"); mainpanel.add(but2); frame.add(mainpanel); frame.setvisible(true);

54 Graphical User Interface