CSE 115 1st Edition Exam #2 Study Guide Lectures 10-15Lecture 10 ( 3/2)Variables, Composition, Naming Conventions, Object Behaviors- Local Variableo Declared within the constructor (method)o Scope = point of declaration to the end of method braceo Stored in stack- Instance Variableo Declared in the class body (before the constructor)o Scope = entire class bodyo Stored in heap- Binary Relationships – Compositiono Whole-part relationshipo Source: wholeo Target: part- Naming Conventionso Can have: Capital letters Lowercase  Digits (0-9) Underscore First character can be a digito Package names  All lowercase (can include underscores between words)o Class names First character: Uppercase Camel case after first word TheFirstExampleo Instance variables First character: Underscore Second character: Lowercase Camel case after first word _thisFirstExamplecse115.WholeWhole()cse115.PartPart()o Local variables First character: Lowercase Camel case after first word thisFirstExample- Object Behaviorso Constructors Called during object creation (during “new”)o Behaviors Called on existing objects (methods)Lecture 11 (3/4)Composition Object Diagram, Association, Accessor and Mutator Methods - Compositiono Source class uses instance variable for target variableo package cse115;public class Dog {private Tail _tail;public Dog () {_tail = new Tail();}}- Binary Relationships – Associationo No lifetime linko Whole takes no responsibility for creating Partcse115.WholeWhole(part)o public class Dog {private Collar _myCollar;public Dog(collar c) {_myCollar = c;o One object can communicate with anothero Objects in the relationship can change over timeo Target (collar) must exist before the Source (Dog) can be created Collar object must be provided in the constructor of the Dog object- Mutator methodso Change the value of an instance variableo public Dog(collar c) {cse115.PartPart()_collar = c;}public void setCollar(collar c) {_collar = c;}}- Constructors vs. Mutatorso Constructors set the value of the instance variable when the class is instantiated o Mutators set the value of the instance variable after the object already existso Constructors initialize all instance variableso Mutatorssets value of just one instance variable- Accessor Methodo Read value of private objectso publicexample1.Terrarium getTerrarium() {return_t;}}Lecture 12 (3/6)Association Object Diagram- Associationo public class Shape {privatejava.awt.Color _color;public Shape(java.awt.Color c) {_color = c;}Shape s1 = new Shape(java.awt.Color.BLUE)}Lecture 13 (3/9/15)s1cShapejava.awt.Color.BLUE_colorContainers, Components, Primitive Types, Layout Manager, java.lang package- Containerso Able to hold graphical objects (containers and objects)- Components o Must be put into containero Able to generate events- Graphical containerso Top level containers Do not need to be place inside any other containers JFrame Multiple paneso Other containers Must be placed in another container JPanel- Create frame, title, make frame visible, make application close when window is closedo package swing;importjavax.swing.JFrame() {privateJFrame _window;publicFirstJFrameExample() {_window = new JFrame(“Title”);_window.setVisible(true);_window.pack();_window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);- Primitive typeso Value is not the same as the objecto No instance variableso Methods can’t be called of themo Boolean Operators: && (AND), || (OR), ! (NOT) Declaration and assignment: boolean x = true;o int Integral value within a range  Operators: +, -, *, /, %- JFrame (Container)o Special methods setVisible (boolean) setDefaultCloseOperation (int) pack()- Layout managemento Layout manager arranges contents of a container using a layout strategyo FlowLayout (default)o panel.setLayout(new BoxLayout(panel, BoxLayout.X_AXIS));o panel.setLayout(new GridLayout(2,2));- java.lang packageo All elements are imported by defaulto java.lang.String String is a class String objects are immutable “This is a String” String concatenation- ‘+’ is a string concatenation operator, binary operator, infix operatoro “The answer is” + “ 17” = The answer is 17 Static methods- Invoked on a class, not an object- No access to instance variables - Invocation record has no “this”- Main Methodo Standard entry point for a Java programo public static void main (String [] args) {newClassName();} Static variables- Accessed via a class, not an object- Often declared public- All uppercase class name (java.awt.Color.BLUE)- Only exists once in memoryo java.lang.System System.out.println() System class is defined in java.lang package “out” is a public static variable of System class whose type is PrintStream the “PrintStream” class defines static method “println”- JButton (Component)o Typically set up to react to clickso Events Clicks on buttons, mouse movements = events A program can react to events by setting up event handlers Event handlers define what should happen when an event occurs Observer pattern: a component which gives rise to an event is decoupled from the part of code that handles the eventLecture 14 (3/13)Observer Pattern (Event and EventHandlers), Interfaces, Realization- Observer pattern in Javao Observer is called a listenero Button clicks are ActionEventso Handlers for ActionEvents are ActionListenerso Use “addActionListener” method to register a listener with a componento Invariant = event generator (JButton)o Variant = event handler (ActionListenerimplementor)- Interfaces and Realizatono Interfaces An interface is a collection of abstract methods Implemented by a class (public class ClassName implements InterfaceName) Contains behaviors that are implemented by a class Methods within an interface do not return a value (public void methods)o Realization Implementing an interface public class EventHandler1 implements ActionListener {public void actionPerformed(ActionEvent e) {System.out.println(“Something”);}} *SeparateActionListener class must be created and the .addActionListener method must be called on to the object in the Model classLecture 15 3/25Relationship between Model, View, and EventHandler classes- Modelo Create instance variables for the objectsJButton Object(Observable)AssociationEvent Handling Object(Observer)Respond to button clickDraws shape of buttono