ObjectEditor Prasun Dewan Comp 114

ObjectEditor Automatic user-interface generation. You only write computation code Separate object to do I/O Main just instantiates it Can replace it with own UI later. Serves as training wheels Serves to separate UI from computation

Example Class package bmi; public class ABMICalculator implements BMICalculator { public double calculateBMI (double weight, double height) { return weight/(height*height); }

Example Main Class package main; import bus.uigen.ObjectEditor; import bmi.ABMICalculator; public class ABMIDisplayer { public static void main(String[] args) { ObjectEditor.edit(new ABMICalculator()); }

ABMICalculator UI

Adding a library in JBuilder

Location of Libraries Use Internet explorer (not Netscape) to download files Library names –oe.jar –shapes.jar oe2.jar version 2 of oe.jar Try oe2 first and in case of bugs use oe.jar oe.jar used by comp14 students oe has lots of bugs! Send me mail for workarounds bugs.

Location of Libraries

What-if BMI Calculations Unchanging value retyped

BMI Spreadsheet State: Data Remembered by an Object between computations

Instance Variables ABMICalculator Instance calculateBMI Parameters Body accesses ABMISpreadsheet Instance getBMI Instance Variables Body accesses Belong to a single method Belong to all methods of an instance local variableglobal variable

State-less Vs State-ful Objects ~ car radios without presets ~ car radios with presets Identical Instances Different Instances

ABMISpreadsheet public class ABMISpreadsheet { double height, weight; public double getHeight() { return height; } public void setHeight(double newHeight) { height = newHeight; } public double getWeight() { return weight; } public void setWeight(double newWeight) { weight = newWeight; } public double getBMI() { return weight/(height*height); } Height Weight BMI

public class C { } Read-Only and Editable Properties public T getP() {... } Typed, Named Unit of Exported Object State Name: P Type: T Readonly public void setP(T newValue) {... } Editable newP obtainP Violates Bean Conventions Bean Conventions for humans tools Getter method Setter method

Properties Classification public class ABMISpreadsheet { double height; public double getHeight() { return height; } public void setHeight(double newHeight) { height = newHeight; } double weight; public double getWeight() { return weight; } public void setWeight(double newWeight) { weight = newWeight; } public double getBMI() { return weight/(height*height); } … Height Weight BMI Editable Read-only Independent Dependent Read-Only

Calling Getter and Setter Methods When ObjectEditor window is created Getter method of each property called to display initial value of property When property is changed to a new value Setter method of property is called with new value as actual parameter Getter method of each property is called to refresh display

Calling Getter and Setter Methods public class ABMISpreadsheet { double height = 1.77; public double getHeight() { return height; } public void setHeight(double newHeight) { height = newHeight; } double weight = 77; public double getWeight() { return weight; } public void setWeight(double newWeight) { weight = newWeight; } public double getBMI() { return weight/(height*height); }

Tracing Method Calls public class ABMISpreadsheet { double height = 1.77; public double getHeight() { System.out.println (“getHeight Called”); return height; } public void setHeight(double newHeight) { System.out.println (“setWeight Called”); height = newHeight; } double weight = 77; public double getWeight() { System.out.println (“getWeight Called”); return weight; } public void setWeight(double newWeight) { System.out.println (“setWeight Called”); weight = newWeight; } public double getBMI() { System.out.println (“getBMI Called”); return weight/(height*height); }

Actual Trace

Modified ABMISpreadsheet public class ABMISpreadsheet { double height, weight; public double getHeight() { return height; } public void setHeight(double newHeight) { height = newHeight; } public double getWeight() { return weight; } public void setWeight(double newWeight) { weight = newWeight; } public double getBMI() { return calculateBMI(weight, height); } public double calculateBMI(double weight, double height) { return weight / (height*height); | } How will above UI change?

Properties + Class Menu

Editing in slow motion : Initial value

Editing in slow motion: text string edited

Editing in slow motion: return triggers setter and getter calls

Renaming getter method public class ABMISpreadsheet { double height, weight; public double height() { return height; } public void setHeight(double newHeight) { height = newHeight; } public double getWeight() { return weight; } public void setWeight(double newWeight) { weight = newWeight; } public double getBMI() { return calculateBMI(weight, height); } public double calculateBMI(double weight, double height) { return weight / (height*height); | }

ObjectEditor does not know it is getter

Reducing Access public class ABMISpreadsheet { double height, weight; double getHeight() { return height; } public void setHeight(double newHeight) { height = newHeight; } public double getWeight() { return weight; } public void setWeight(double newWeight) { weight = newWeight; } public double getBMI() { return calculateBMI(weight, height); } public double calculateBMI(double weight, double height) { return weight / (height*height); | }

Height is not a readable property

Changing setter public class ABMISpreadsheet { double height, weight; public double getHeight() { return height; } public int setHeight(double newHeight) { height = newHeight; return height; } public double getWeight() { return weight; } public void setWeight(double newWeight) { weight = newWeight; } public double getBMI() { return calculateBMI(weight, height); } public double calculateBMI(double weight, double height) { return weight / (height*height); | }

Height is not a writeable property

An alternative class public class AStringHistory implements StringHistory { public static final int MAX_SIZE = 50; String[] contents = new String[MAX_SIZE]; int size = 0; public int size() { return size;} public String elementAt (int index) { return contents[index]; } boolean isFull() { return size == MAX_SIZE; } public void addElement(String element) { if (isFull()) System.out.println("Adding item to a full history"); else { contents[size] = element; size++; } Variable number of dynamically created indexed properties

ObjectEditor Conventions for Variable-Sized Collection public interface I { public void addElement (T t); public T elementAt (int index); public int size(); } Arbitrary Type (Must be Object Type to be recognized by ObjectEditor) Read methods Write method (name does not matter to OE)

Initial State

Adding an element Name does not matter to ObjectEditor

Adding an element

ObjectEditor calls all elementAt () and getter() methods after each method call

Adding another element

Public Class Constants

Non Public Class Constant public class AStringHistory implements StringHistory { static final int MAX_SIZE = 50; String[] contents = new String[MAX_SIZE]; int size = 0; public int size() { return size;} public String elementAt (int index) { return contents[index]; } boolean isFull() { return size == MAX_SIZE; } public void addElement(String element) { if (isFull()) System.out.println("Adding item to a full history"); else { contents[size] = element; size++; }

Non-Public Class Constant Non constants menu

Public Instance Constant public class AStringHistory implements StringHistory { public final int MAX_SIZE = 50; String[] contents = new String[MAX_SIZE]; int size = 0; public int size() { return size;} public String elementAt (int index) { return contents[index]; } boolean isFull() { return size == MAX_SIZE; } public void addElement(String element) { if (isFull()) System.out.println("Adding item to a full history"); else { contents[size] = element; size++; }

Public Instance Constant Public instance variables also displayed. Considered part of displayable instance state. Breaking of encapsulation is visible in the display!

Mixing static and dynamic properties

Another UI

New Class (edit) public class AStringHistory implements StringHistory { public static final int MAX_SIZE = 50; String[] contents = new String[MAX_SIZE]; int size = 0; public int size() { return size;} public String elementAt (int index) { return contents[index]; } boolean isFull() { return size == MAX_SIZE; } public void addElement(String element) { if (isFull()) System.out.println("Adding item to a full history"); else { contents[size] = element; size++; }

New Class (edited) public class AStringHistory implements StringHistory { public static final int MAX_SIZE = 50; String[] contents = new String[MAX_SIZE]; int size = 0; public int size() { return size;} public String elementAt (int index) { return contents[index]; } boolean isFull() { return size == MAX_SIZE; } String newString = “”; public String getNewString() {return newString;} public void setNewString(String newVal) { addElement(newVal); newString = newVal; } …. }

New Class public class AStringHistory implements StringHistory { String newString = ""; public void setNewString(String newVal ) { newString = newVal; addElement(newString); } public String getNewString() { return newString; } public static final int MAX_SIZE = 50; String[] contents = new String[MAX_SIZE]; int size = 0; public int size() { return size;} public String elementAt (int index) { return contents[index]; } boolean isFull() { return size == MAX_SIZE; } public void addElement(String element) { … }

Uninitialized properties public class AStringHistory implements StringHistory { String newString; public void setNewString(String newVal ) { newString = newVal; addElement(newString); } public String getNewString() { return newString; } public static final int MAX_SIZE = 50; String[] contents = new String[MAX_SIZE]; int size = 0; public int size() { return size;} public String elementAt (int index) { return contents[index]; } boolean isFull() { return size == MAX_SIZE; } public void addElement(String element) { … }

Uninitialized properties

Non-public size() public class AStringHistory implements StringHistory { String newString; public void setNewString(String newVal ) { newString = newVal; addElement(newString); } public String getNewString() { return newString; } public static final int MAX_SIZE = 50; String[] contents = new String[MAX_SIZE]; int size = 0; int size() { return size;} public String elementAt (int index) { return contents[index]; } boolean isFull() { return size == MAX_SIZE; } public void addElement(String element) { … }

Non-public size() ObjectEditor discovers only one fixed property

“Recursion” in ObjectEditing package main; import bus.uigen.ObjectEditor; public class AnObectEditorDisplayer { public static void main(String[] args) { ObjectEditor.edit(new ObjectEditor()); }

ObjectEditor Properties

ObjectEditor Properties and Commands

Newly instantiated and displayed object

Bean Methods Getters and setters shown in separate menu Usually invoked implicitly as side effect of editing

“Recursion” in ObjectEditing package main; import bus.uigen.ObjectEditor; public class AnObectEditorDisplayer { public static void main(String[] args) { ObjectEditor.edit(new ObjectEditor()); } Application-independent! ObjectEditor has a main method that does this automatically!

Running ObjectEditor java bus.uigen.ObjectEditor = ObjectEditor.edit(new ObjectEditor()) java bus.uigen.ObjectEditor C = ObjectEditor.edit (new C())

Running ObjectEditor Main

Object parameters

Constructors with parameters

Interface

Constructors with parameters