About Object-Oriented Programming

If you are a newbie, please advise.

My understanding about Object-Oriented Programming

1)Encapsulate attributes and behaviors of common things

2)Separation of interfaces and Implementations

If there is one sentence, it is "instantiating various objects with a class ".

The following is an article I have seen in cool shell: How to understand object-oriented programming.

For the three-Section code.

This is the initial version.

public class PrintOS{    public static void main(final String[] args)    {        String osName = System.getProperty("os.name") ;        if (osName.equals("SunOS") || osName.equals("Linux"))        {            System.out.println("This is a UNIX box and therefore good.") ;        }        else if (osName.equals("Windows NT") || osName.equals("Windows 95"))        {            System.out.println("This is a Windows box and therefore bad.") ;        }        else        {            System.out.println("This is not a box.") ;        }    }}

The next step is the procedural version.

Procedural Solution

public class PrintOS{    private static String unixBox()    {        return "This is a UNIX box and therefore good." ;    }    private static String windowsBox()    {        return "This is a Windows box and therefore bad." ;    }    private static String defaultBox()    {        return "This is not a box." ;    }    private static String getTheString(final String osName)    {        if (osName.equals("SunOS") || osName.equals("Linux"))        {            return unixBox() ;        }        else if (osName.equals("Windows NT") ||osName.equals("Windows 95"))        {            return windowsBox() ;        }        else        {            return defaultBox() ;        }    }    public static void main(final String[] args)    {        System.out.println(getTheString(System.getProperty("os.name"))) ;    }}

Next is the naive object-oriented programming.

Naive Object-Oriented Programming

PrintOS. java

public class PrintOS{    public static void main(final String[] args)    {        System.out.println(OSDiscriminator.getBoxSpecifier().getStatement()) ;    }}

OSDiscriminator. java

public class OSDiscriminator // Factory Pattern{    private static BoxSpecifier theBoxSpecifier = null ;    public static BoxSpecifier getBoxSpecifier()    {        if (theBoxSpecifier == null)        {            String osName = System.getProperty("os.name") ;            if (osName.equals("SunOS") || osName.equals("Linux"))            {                theBoxSpecifier = new UNIXBox() ;            }            else if (osName.equals("Windows NT") || osName.equals("Windows 95"))            {                theBoxSpecifier = new WindowsBox() ;            }            else            {                theBoxSpecifier = new DefaultBox () ;            }        }        return theBoxSpecifier ;    }}

BoxSpecifier. java

public interface BoxSpecifier{    String getStatement() ;}

DefaultBox. java

public class DefaultBox implements BoxSpecifier{    public String getStatement()    {        return "This is not a box." ;    }}

UNIXBox. java

public class UNIXBox implements BoxSpecifier{    public String getStatement()    {        return "This is a UNIX box and therefore good." ;    }}

WindowsBox. java

public class WindowsBox implements BoxSpecifier{    public String getStatement()    {        return "This is a Windows box and therefore bad." ;    }}

OO master's Solution

PrintOS. java

public class PrintOS{    public static void main(final String[] args)    {        System.out.println(OSDiscriminator.getBoxSpecifier().getStatement()) ;    }}

OSDiscriminator. java

public class OSDiscriminator // Factory Pattern{    private static java.util.HashMap storage = new java.util.HashMap() ;                                                                                                                                                                                  public static BoxSpecifier getBoxSpecifier()    {        BoxSpecifier value = (BoxSpecifier)storage.get(System.getProperty("os.name")) ;        if (value == null)            return DefaultBox.value ;        return value ;    }    public static void register(final String key, final BoxSpecifier value)    {        storage.put(key, value) ; // Should guard against null keys, actually.    }    static    {        WindowsBox.register() ;        UNIXBox.register() ;        MacBox.register() ;    }}

BoxSpecifier. java

public interface BoxSpecifier{    String getStatement() ;}

DefaultBox. java

public class DefaultBox implements BoxSpecifier // Singleton Pattern{    public static final DefaultBox value = new DefaultBox () ;    private DefaultBox() { }    public String getStatement()    {        return "This is not a box." ;    }}

UNIXBox. java

public class UNIXBox implements BoxSpecifier // Singleton Pattern{    public static final UNIXBox value = new UNIXBox() ;    private UNIXBox() { }    public  String getStatement()    {        return "This is a UNIX box and therefore good." ;    }    public static final void register()    {        OSDiscriminator.register("SunOS", value) ;        OSDiscriminator.register("Linux", value) ;    }}

WindowsBox. java

public class WindowsBox implements BoxSpecifier  // Singleton Pattern{    public  static final WindowsBox value = new WindowsBox() ;    private WindowsBox() { }    public String getStatement()    {        return "This is a Windows box and therefore bad." ;    }    public static final void register()    {        OSDiscriminator.register("Windows NT", value) ;        OSDiscriminator.register("Windows 95", value) ;    }}

MacBox. java

public class MacBox implements BoxSpecifier // Singleton Pattern{    public static final MacBox value = new MacBox() ;    private MacBox() { }    public  String getStatement()    {        return "This is a Macintosh box and therefore far superior." ;    }    public static final void register()    {        OSDiscriminator.register("Mac OS", value) ;    }}

The code of the above versions makes me feel more and more difficult to understand. Originally, if-else statements or switch statements can be used to implement the required functions in a simple and clear way. Object-Oriented Programming is designed to make development more efficient and convenient for us. However, the above object-oriented method makes it a little superfluous. We should make rational use of object-oriented programming instead of abuse.

This article is from the "Calm dreamer" blog, please be sure to keep this source http://idiotxl1020.blog.51cto.com/6419277/1288523