新手上路，请多指教。
关于面向对象编程，我的理解
1)封装具有共性的事物属性和行为
2)接口和实现的分离
如果有一句话来说的话，那就是“用一个类去实例化各种各样的对象”。
下面是我在所看到的一篇文章。
关于里面的三段代码。
这是最初的版本。
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.") ; } }}
接着就是过程化的版本。
过程化的方案
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"))) ; }} 接下来是幼稚的面向对象编程
幼稚的面向对象编程
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大师的方案
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) ; }} 上面几个版本的代码，给我的感觉是越来越来难看懂，本来用if-else语句或者switch语句就可以简单明了的实现所需要的功能。面向对象编程是为了方便我们，使得我们的开发更加的高效率。可是，上面的面向对象反而使得有点画蛇添足。应该合理的运用面向对象编程，而不是滥用。