Home > Articles > Programming

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

Large Class

Symptoms

  • Large number of instance variables

  • Large number of methods

  • Large number of lines

Causes

Large classes get big a little bit at a time. The author keeps adding just one more capability to a class until eventually it grows too big. Sometimes the problem is a lack of insight into the parts that make up the whole class. In any case, the class represents too many responsibilities folded together.

What to Do

In general, you're trying to break up the class. If the class has Long Methods, address that smell first. To break up the class, three approaches are most common:

  • Extract Class, if you can identify a new class that has part of this class's responsibilities

  • Extract Subclass, if you can divide responsibilities between the class and a new subclass

  • Extract Interface, if you can identify subsets of features that clients use

Sometimes, the class is big because it's a GUI class, and it represents not only the display component, but the model as well. In this case, you can use Duplicate Observed Data to help extract a domain class.

Payoff

Improves communication. May expose duplication.

EXERCISE 5

Large Class.

Consider this declaration from the Java libraries:

public class JTable extends JComponent
  implements Accessible, CellEditorListener,
     ListSelectionListener, Scrollable,
     TableColumnModelListener, TableModelListener
{
// Constants
public static final int AUTO_RESIZE_ALL_COLUMNS
public static final int AUTO_RESIZE_LAST_COLUMN
public static final int AUTO_RESIZE_NEXT_COLUMN
public static final int AUTO_RESIZE_OFF
public static final int AUTO_RESIZE_SUBSEQUENT_COLUMNS

// Constructors
public JTable()
public JTable(TableModel, TableColumnModel)
public JTable(TableModel, TableColumnModel, ListSelectionModel)
public JTable(int, int)
public JTable(Object[][], Object[][])
public JTable(java.util.Vector, java.util.Vector)

// Methods
public void addColumn(TableColumn column)
public void addColumnSelectionInterval(int start, int finish)
public void addNotify()
public void addRowSelectionInterval(int start, int finish)
public void clearSelection()
public void columnAdded(TableColumnModelEvent event)
public void columnAtPoint(Point p)
public void columnMarginChanged(ChangeEvent event)
public void columnMoved(TableColumnModelEvent event)
public void columnRemoved(TableColumnModelEvent event)
public void columnSelectionChanged(ListSelectionEvent event)
public void convertColumnIndexToModel(int viewColumn)
public void convertColumnIndexToView(int modelColumn)
public void createDefaultColumnsFromModel()
public boolean editCellAt(int row, int column)
public boolean editCellAt(int row, int column, EventObject event)
public void editingCanceled(ChangeEvent event)
public void editingStopped(ChangeEvent event)
public AccessibleContext getAccessibleContext()
public boolean getAutoCreateColumnsFromModel()
public int getAutoResizeMode()
public TableCellEditor getCellEditor()
public TableCellEditor getCellEditor(int row, int column)
public Rectangle getCellRect(int row, int column, boolean includeSpacing)
public boolean getCellSelectionEnabled()
public TableColumn getColumn(Object object)
public Class getColumnClass(int column)
public int getColumnCount()
public TableColumnModel getColumnModel()
public String getColumnName(int column)
public Boolean getColumnSelectionAllowed()
public TableCellEditor getDefaultEditor(Class class)
public TableCellRenderer getDefaultRenderer(Class class)
public int getEditingColumn()
public int getEditingRow()
public Component getEditorComponent()
public Color getGridColor()
public Dimension getIntercellSpacing()
public TableModel getModel()

public Dimension getPreferredScrollableViewportSize()
public int getRowCount()
public int getRowHeight()
public int getRowMargin()
public Boolean getRowSelectionAllowed()

public int getScrollableBlockIncrement(
Rectangle visible, int orientation, int direction)
public Boolean getScrollableTracksViewportHeight()
public Boolean getScrollableTracksViewportWidth()
public int getScrollableUnitIncrement(
Rectangle visible, int orientation, int direction)
public int getSelectedColumn()
public int getSelectedColumnCount()
public int[] getSelectedColumns()
public int getSelectedRow()
public int getSelectedRowCount()
public int[] getSelectedRows()
public Color getSelectionBackground()
public Color getSelectionForeground()
public ListSelectionModel getSelectionModel()
public Boolean getShowHorizontalLines()
public Boolean getShowVerticalLines()
public JTableHeader getTableHeader()
public String getToolTipText(MouseEvent event)
public TableUI getUI()
public String getUIClassID()
public Object getValueAt(int row, int column)
public Boolean isCellEditable(int row, int column)
public Boolean isCellSelected(int row, int column)
public Boolean isColumnSelected(int column)
public Boolean isEditing()
public boolean isManagingFocus()
public Boolean isRowSelected(int row)
public void moveColumn(int column, int newColumn)
public Component prepareEditor(TableCellEditor editor,
 int row, int column)
public Component prepareRenderer(TableCellRenderer renderer,
 int row, int column)
public void removeColumn(TableColumn column)
public void removeColumnSelectionInterval(int column1, int column2)
public void removeEditor()
public void removeRowSelectionInterval(int row1, int row2)
public void reshape(int x, int y, int width, int height)
public int rowAtPoint(Point point)
public void selectAll()
public void setAutoCreateColumnsFromModel(Boolean doAutoCreate)
public void setAutoResizeModel(int mode)
public void setCellEditor(TableCellEditor editor)

public void setCellSelectionEnabled(Boolean maySelect)
public void setColumnModel(TableColumnModel model)
public void setColumnSelectionAllowed(Boolean maySelect)
public void setColumnSelectionInterval(int column1, int column2)
public void setDefaultEditor(Class class, TableCellEditor editor)
public void setDefaultRenderer(Class class, TableCellRenderer renderer)
public void setEditingColumn(int column)
public void setEditingRow(int row)
public void setGridColor(Color color)
public void setIntercellSpacing(Dimention dim)
public void setModel(TableModel model)
public void setPreferredScrollableViewportSize(Dimension dim)
public void setRowHeight(int height)
public void setRowMargin(int margin)
public void setRowSelectionAllowed(Boolean maySelect)
public void setSelectionBackground(Color background)
public void setSelectionForeground(Color foreground)
public void setSelectionMode(int mode)
public void setSelectionModel(ListSelectionModel model)
public void setShowGrid(Boolean showing)
public void setShowHorizontalLines(Boolean b)
public void setShowVerticalLines(Boolean b)
public void setTableHeader(JTableHeader header)
public void setUI(TableUI ui)
public void setValueAt(Object value, int row, int column)
public void sizeColumnsToFit(int resizingColumn)
public void tableChanged(TableModelEvent event)
public void updateUI()
public void valueChanged(ListSelectionEvent)

// plus 22 protected variables

// plus 10 protected methods

// plus 97 methods inherited from JComponent (and fields etc.)

// plus about 35 methods from Container

// plus about 85 methods from Component

// plus 11 methods from Object
}
  1. Why does this class have so many methods?

  2. Go through the methods listed and categorize them into 5 to 10 major areas of responsibility.

  3. In what ways could the library writers have eliminated some of these methods?

  4. In Java, Object has 11 methods. In Smalltalk, it has more than 100. Why the difference? Talk to a Smalltalk person and find out why and whether or not this is a smell.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020