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LETU COSC 2103 - Introduction to Classes and Objects

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Chapter 33.2 Classes, Objects, Methods and Instance Variables3.3 Declaring a Class with a Method and Instantiating an Object of a ClassOutlineClass GradeBookClass GradeBookTestSlide 7Compiling an Application with Multiple Classes3.4 Declaring a Method with a ParameterSlide 10Notes on Import Declarations3.5 Instance Variables, set Methods and get MethodsAccess Modifiers public and privateGradeBookTest Class That Demonstrates Class GradeBookPrimitive Types vs. Reference Types3.7 Initializing Objects with ConstructorsAccountTest Class to use Class AccountDisplaying Text in a Dialog BoxSlide 19Entering Text in a Dialog Box1Chapter 3Introduction to Classes and Objects23.2 Classes, Objects, Methods and Instance Variables•Class provides one or more ____________•Method represents ____________ in a program•Describes the mechanisms that actually perform its tasks•______________ from its user the complex tasks that it performs•Method call tells method to perform its task•Classes contain one or more ______________•Specified by ________________ variables•Carried with the object as it is used33.3 Declaring a Class with a Method and Instantiating an Object of a Class•Each class declaration that begins with keyword _________________ •must be stored in a file •that has the _________________________________ and •ends with the _____________ file-name extension.4OutlineGradeBook.javaPrint line of text to outputPrint line of text to output5Class GradeBook•keyword public is an access modifier •Class declarations include:•Access ________________________•Keyword cl ass•Pair of left and right _________________•Method declarations•Keyword __ _____________ indicates method is available to public•Keyword vo id indicates ___________________•Access modifier, return type, name of method and parentheses comprise method _____________6Class GradeBookTest•Java is ___________________•Programmers can create new classes•Test program uses the GradeBook class•Class instance creation expression•Keyword ________________•Then name of class to create and parentheses•Calling a method•Object ___________, then dot separator (.)•Then _____________ name and parentheses7OutlineUse class instance creation expression to create object of class GradeBookUse class instance creation expression to create object of class GradeBookCall method displayMessage using GradeBook objectCall method displayMessage using GradeBook object8Compiling an Application with Multiple Classes•Note we have two classes•Gradebook•GradeBookTest•Compiling multiple classes•Use the compile command in the IDE•Compile each _____________ separately•Requires a _____________ in some IDE’s•Project created in JCreator, Eclipse•Just keep in same directory in “Ready”93.4 Declaring a Method with a Parameter•Method parameters•Additional __________________ passed to a method•Supplied in the method call with arguments•Scanner methods•nextLine reads next _________ of input•next reads next ________ of input10OutlineGradeBook.javaCall printf method with courseName argumentCall printf method with courseName argumentView Fig. 3.5GradeBook test programView Fig. 3.5GradeBook test program11Notes on Import Declarations•____________________ is implicitly imported into every program•Default package•Contains classes compiled in the same directory•Implicitly imported into source code of other files in directory•Packages unnecessary if fully-qualified names are used123.5 Instance Variables, set Methods and get Methods•Variables declared in the body of method•Called local variables•Can only be used ______________________•Variables declared in a ________ declaration•Called _____________ or instance variables•Each object of the class has a separate instance of the variable•Note set and get methods13Access Modifiers public and private•private keyword•Used for most _____________ variables•private variables and methods are accessible only to _____________________ in which they are declared•Declaring instance variables private is known as _______________________•Return type•Indicates item returned by method•Declared in _____________________14GradeBookTest Class That Demonstrates Class GradeBook•Default initial value•Provided for all fields not initialized•Equal to ____________ for Strings•Note private instance variables•Cannot be accessed directly by ___________________________•Use set methods to ____________ the value•Use _________ methods to retrieve the value15Primitive Types vs. Reference Types•Types in Java•_________________________•boolean, byte, char, short, int, long, float, double•______________________ (sometimes called nonprimitive types)•Objects•Default value of null•Used to invoke an object’s methods163.7 Initializing Objects with Constructors•Constructors•_______________ an object of a class•Java requires a constructor for every class•Java will provide a _________________ constructor if none is provided•Called when keyword new is followed by the _____________ and ______________•Constructors which ________ “incoming” initial value17AccountTest Class to use Class Accou nt•Note use of Scanner object•Input floating point number•Note use of format specifier %f•Used to output floating-point numbers•Place a _____________________ between the percent sign and the f to mandate a precision18Displaying Text in a Dialog Box•Windows and dialog boxes•Many Java applications use these to __________________•JOptionPane provides prepackaged ________________ called message dialogs•Program to use dialog box19Displaying Text in a Dialog Box•Package javax.swing•Contains classes to help create graphical user interfaces ________________•Contains class JOptionPane•Declares ____________ method showMessageDialog for displaying a message dialog20Entering Text in a Dialog Box•Input dialog•Allows user to input information•Created using method showInputDialog from class


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LETU COSC 2103 - Introduction to Classes and Objects

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