Overview of Eclipse

7/30/2019 Overview of Eclipse

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Overview of Eclipse Lectures

1. Overview

2. Installing and Running

3. Building and Running Java Classes

4. Refactoring

5. Debugging

6. Testing with JUnit

7. Version Control with CVS


4. Refactoring Lecture 2

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Module Road Map1. Overview2. Installing and Running

3. Building and Running Java Classes Developing Java applications Projects, packages, classes Browsing Java code Searching Java code Organizing Java code Using Code Assist Running Java applications

Scrapbook4. Refactoring5. Debugging6. Testing with JUnit7. Version Control with CVS


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Building and Running Java Classes Using Code Assist

When activated, code assist opens a list ofavailable code completions

Code Assist activates by Crtl+Space Activates automatically when a message needs to be

sent to an object (after the dot is typed)

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Building and Running Java Classes Using Quick Fix Useful if Java compiler shows errors

Gives options for fixing the errors

Activated through Edit Quick Fix menu option

Error indication


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Building and Running Java Classes

Searching for Java Classes

When developing Java application a good searchmechanism is very important

You often search for class, method declarations, andreferences

It is important to be able to find things quickly

Eclipse Java Search mechanism is very extensive

It allows you to search for:

Types, methods, constructors, packages, and fields

Declarations, Implementers, References

In the scope of Workspace, Working Set, or SelectedResources

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Building and Running Java Classes Running Java Classes To Run Java

application

Choose Run Run from themenu

Standard Javaoutput isdisplayed in the

console window


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Building and Running Java Classes Console View

Represents standard Java console Opens by default when standard Java output

is used

Can also be open from Window Show Viewmenu System.out.println("Hello World");

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Building and Running Java Classes Scrapbook Allows for writing and executing of Java code

Very useful for quick test of Java code that youwrite

The Java code in the Scrapbook can be:

Displayed as a string when evaluated

Inspected when evaluated

Opens an Inspector view where you can see returningobject from evaluation and all containing fields

Executed


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Building and Running Java Classes Scrapbook

It is created by selecting aproject and choosing New Otherfrom the PackageExplorers context menu

This opens up the Newdialog box

Expand Java Expand Java Run/Debug

under Java Select Scrapbook page and

click Next. This will open New

Scrapbook page Enter the name of the page

Your scrapbook page willbecome a resource in yourproject

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Building and Running Java Classes Scrapbook To open the scrapbook

page just click on theresource

It opens up like a Javasource file editor

Type Java code andselect the context

menu to Display orInspect


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Building and Running Java Classes Scrapbook

Class names must be fullyqualified in what you type

Set imports to make lifeeasier

Think of your scrapbook asa page that Eclipse willtake the source you type,wrap it in a class with yoursource in the main menu,then compile and execute

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Building and Running Java Classes Summary You have learned:

How to create projects, packages and classes

How to browse Java code and search for Java

code

How to use coding assistance

How to run Java code

How to use the Scrapbook


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Exercise 2

Create a new class titled and add it to the package in the projectyou have created in Exercise 1.

Add a private integer field (member variable) to the class .

Add a constructor method to accept an integer to initialize the private integer field .

Add a public method that takes no parameters and returns void.

Add code to the method to print the value of the private variable to thestandard output.

Instantiate an object of type in the routine of the .

Call the routine of the object.

Run the project .

What do you see in the Console window?

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Module Road Map1. Overview

2. Installing and Running


4. Refactoring

Why Refactoring?

Examples

Common Refactorings

5. Debugging6. Testing with JUnit

7. Version Control with CVS


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Refactoring Organizing Java Code

Eclipse comes with extensive support fororganizing and refactoring Java code

It is possible to:

Generate getters and setters for the fields

Organize missing import statements

Move fields, methods, classes

Rename methods, classes, packages

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Refactoring What is Refactoring? Refactoring is the process of changing a

software system so that

the external behavior is not altered, but

the internal structure is improved.

Refactoring (http://www.refactoring.com/) is abehavior-preserving transformation.


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Refactoring Why Refactoring?

Methods might no longer do (only) what theirname suggests.

Functionality that should be in two differentclasses might be in the same class.

Functionality that should be in one classmight be duplicated in two or more classes.

Improve the design of existing code.

Gain a better understanding of the code.

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Refactoring Example Consider a method for computing the room

charge for a hotel:public doublepublic doublepublic doublepublic double getRoomChargegetRoomChargegetRoomChargegetRoomCharge()()()()

{{{{

doubledoubledoubledouble roomChargeroomChargeroomChargeroomCharge = 0.0;= 0.0;= 0.0;= 0.0;

... code to compute room charge...... code to compute room charge...... code to compute room charge...... code to compute room charge...

returnreturnreturnreturn roomChargeroomChargeroomChargeroomCharge;;;;

}}}}

What other factors might go into computingthe room charge?


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Refactoring Example

Of course, to print out a bill for a customer, we also need to includeincidentals and taxes

Whats inelegant about this method now?

3 sets of calculations in one function. Method does 3 things. The name is not illustrative of what the method does.

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Refactoring Example Better: Changing the name of the method (for

example, calculateCustomerChargecalculateCustomerChargecalculateCustomerChargecalculateCustomerCharge).

Does this fix the problem?

No, We also need to change the name at all call sites.

We need to update the documentation.

If this method overrides a method in another class, theother name may need to be changed too. Ditto if thismethod implements an interface.

This is known as the Rename Methodrefactoring.


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Refactoring Example

Lets refactor our getRoomChargegetRoomChargegetRoomChargegetRoomCharge()()()() method.

What have we done? We defined additional methods to compute incidentals, tax, etc.

In order to do this, we added local variables for the quantities thatare being calculated in the new methods.

Some pre-existing local variables ended up being parameters to the

new method. The returned value is different from what was returned in the pre-

existing method.

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Refactoring Common Refactorings Rename

Methods, Fields, Packages, Projects, Parameters, orLocal Variables

Encapsulate Field(generate getter and setter)

Pull upa Fieldor Method(into superclass)

Push downa Fieldor Method(into subclass)

Extract Method, Local Variable, or Constantfrom

an Expression Change Method Signature


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Refactoring Encapsulating a Field

After refactoring, we have

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Refactoring Encapsulating a Field Using Eclipse Select the field in one of the Java views

(e.g., Outline, Package Explorer orMembers view).

From the field's pop-up menu, selectRefactor Encapsulate Field , or fromthe menu bar, select Refactor Encapsulate Field

Alternatively, in the Java editor, selectthe field.

From the menu bar, select Refactor Encapsulate Field , or from the editor'spop-up menu, select Refactor Encapsulate Field

This pops up the Encapsulate Field

dialog. Type the names of the accessor routines

in the Getter name and Setter name textfields.

Click Preview to preview the changes orClick OK to perform refactoring.


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Refactoring Pull Up Method

Moves a field or method to a superclass of its declaring class. Suppose you have the same methodor nearly the same methodin

two different classes in your system. It may be a good idea to centralizethe behavior in a superclass.

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Refactoring Pull Up Method After the Pull up Method refactoring is applied

public class Person {

String getName() {

...

}

}


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Refactoring Pull Up Method Using Eclipse

In a Java view (e.g., Outline,Package Explorer, Members),select the members that youwant to pull up.

From the menu bar, selectRefactor Pull Up or from thepop-up menu, select Refactor Pull Up.

This pops up the Pull updialog.

Select the methods to pull upand their new declaring class.Click Next.

Select the methods to be

removed in the subtypes afterpull up and click Next to reviewthe changes.

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Refactoring Push Down Method Reverse of Pull up Method.

Moves a set of methods and fields from aclass to its subclasses.

Can be used when some of the subclassesdo not use a method defined in thesuperclass.


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Refactoring Push Down Method Using Eclipse

In a Java view (e.g.,Outline, Package Explorer,Members), select themembers that you want topush down.

From the menu bar, selectRefactor Push Down orfrom the pop-up menu,select Refactor PushDown.

The Push Down dialog will

open. Click Preview to preview

the changes or click OK toperform the refactoring.

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Refactoring Extracting a Local Variable An expression that occurs in more than one place

is replaced with a local variable, whose value iscalculated only once.

If a program needs to use the same value inmultiple places, it can be calculated only once andthen used wherever needed.

Advantages

Makes the code more efficient. Makes the code more readable.

Creates a single point of maintenance for the logic ofcomputing the expression.


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Refactoring Extracting a Local Variable Using Eclipse

In a Java editor, select theexpression that you want toextract to a local variable.

From the editor's pop-upmenu, select Refactor Extract Local Variable or fromthe menu bar, select Refactor Extract Local Variable.

This will open the ExtractLocal Variable dialog box.

Type the name of the variablein the Variable name textfield.

Click Preview to preview thechanges or click OK to

perform the refactoring.

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Refactoring Extracting a Method Creates a new method containing the statements

or expression currently selected and replaces theselection with a reference to the new method.

Advantages

Code readability

Minimize code duplication


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Refactoring Extracting a Method Using Eclipse

In an editor, select a set ofstatements or an expressionfrom a method body.

From the pop-up menu in theeditor, select Refactor Extract Method from themenu bar, select Refactor Extract Method.

This opens the ExtractMethod dialog box.

Type the method name in theMethod name text field.

In the Access Modifier list,specify the method's visibility(public, default, protected, or

private). Click Preview to preview the

changes or click OK toperform the refactoring.

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Refactoring Change Method Signature Select the method in a Java view (e.g.

Outline, Package Explorer, Members).

From the menu bar, select Refactor Change Method Signature or from themethod's pop-up menu, selectRefactor Change Method Signature.

This opens the Change MethodSignature dialog box.

Use the Access Modifier drop-down tocontrol the method's visibility.

Change the method's return type orname by editing the provided textfields.

Select one or more parameters anduse the Up and Down buttons to

reorder the parameters (you can seea signature preview below theparameter list).

Use the Add button to add aparameter; you can then edit its type,name and default value in the table. Switch to the Exceptions tab to add or

remove thrown exceptions. ClickPreview to preview the changes


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Other Refactorings Supported by Eclipse

Renaming a package

a compilation unit

a type

a local variable

method parameters

Extracting

a constant

an interface from a type

Inlining

a local variable

a method

a constant

static members betweentypes

an instance method to acomponent

Converting a local variable to a field

an anonymous inner class toa nested class

a nested type to a top level

type

Replacing

references to a type with

references to one of itssupertypes

a single reference to a type

with a reference to one of itssupertypes

an expression with a methodparameter

constructor calls with factory

method invocations

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Refactorings Supported by NetBeans (v 5.0) Renaming

a package

a compilation unit

a type

a local variable

method parameters

Extracting

a constant

an interface from a type

Inlining

a local variable

a method

a constant

static members betweentypes

an instance method to acomponent

Converting

a local variable to a field

an anonymous inner class toa nested class

a nested type to a top level

type

Replacing

references to a type with

references to one of itssupertypes

a single reference to a type

with a reference to one of itssupertypes

an expression with a method

parameter

constructor calls with factorymethod invocations


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Exercise 3

Change the name of the class NewClass that wascreated in Exercise 2 in the project EgApp toRefactoredClass.

Change the name of the method printField in theclass RefactoredClass to refactoredPrintField.

Review the changes that will be made by Eclipseusing the Preview option.

Compile and Run the project EgApp.

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