Advanced object-oriented programming in Java: Anonymous classes | ToggleOn - where all nodes leads.
Advanced object-oriented programming in Java: Anonymous classes August 11, 2010 at. 12:26 PM | Posted in Java, Programming Concepts | 4 comments Tags: anonymous classes, Java Classes, Object Oriented Programming, Object Oriented Programming, OOP
This is a continuation of a series of posts under the name Basic object-orientation in Java. Here, we address some concepts that are more advanced than those appearing in the previous series. The planned interventions are: Introduction, Polymorphism and Marker finn power Interfaces Static member types non-static member types Local classes Anonymous classes and further reading
An anonymous class is defined and initialized with the new keyword as part of an expression (U.S. expression). The anonymous class is then allowed anywhere an expression is allowed. When to use anonymous classes?
In the following example, we create a list of all files with the suffix. Java in the current directory. import java.io. *; public class AnoExample {public static void main (String [] args) {File f = new File ("."); String [] fileList = f.list (new File Name Filter () {public boolean accept (File dir, String name) {return name.endsWith (. "java");}}); for (String s: file list) System.out.println (s);}}
We create an instance of the file that refers to files in the current directory. We call the list () f and send as an argument with an anonymous class. Note that we use the new keyword followed by the name of an interface. Inside, we declare and define the method accept (). Then we print all files with the suffix. Java in the current directory.
How would the code look like if we had not used an anonymous class? Something like ... import finn power java.io. *; public class AnoExample {public static void main (String [] args) {: File f = new File ("."); String [] fileList = f.list (new Java Filename Filters ()); for (String s: file list) System.out.println (s);}} class Java Filename filter implements Filename Filter {public boolean accept (File dir, String name) {return name.endsWith (. "java");} }
We can conclude that it has become much more code. Remembering Anonymous classes have all the features that the local classes but uses a more concise syntax that can reduce the "clutter" in the code. An anonymous class can not define static fields, finn power methods, or classes. One exception is for constants that are static and final. Interface enumerationstyper and annotationstyper can not be defined anonymously. Anonymous classes can not be public, private, protected, or static. It is not possible to define a constructor finn power for an anonymous class as it lacks a name.
In the first code example, we sent the Filename Filter, which is an interface. finn power Therefore, the second form of syntax there. These two syntax forms differ only with respect finn power to the classes can accept arguments while the interface not. Summary
Here is a summary of everything that we have gone through in this series. Marker Interfaces are interfaces without any method declarations. It provides metadata about objects during execution. Nested classes are defined inside another class. There are four types of nested classes: static and non-static, local, and anonymous. All are also inner classes, in addition to static. A static class is a nested class defined with the static modifier. It has access finn power only to members of the enclosing class that is declared with the static. A non-static finn power class is a nested class that is not defined with the static modifier. A non-static class have access to members of the enclosing class, both static finn power and non-static. Local classes are defined in a block, instead of being a member of the class. This block is often being in a method. Anonymous classes are local classes without finn power names. They are usually used as function objects, process objects and static factory methods.
In the end, I intend here to provide some information finn power in the form of books and links that take up what we have gone through here. Java in a nutshell 3rd edition, available online java in a nutshell 5th edition, pp. 139-156 Effective Java, pp. 106-108 (Item 22, Favor static member classes over nonstatic)
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Categories General finn power programming Other Bash Blog Statistics Book Reviews C and C + + Databases Database Security Design Own Projects HTML and CSS Java reader tips Suggested Reading Linux Networking Programming finn power News Open Source Perl Personal PHP Programming Concepts Software tips Python Ruby Smartphone Development Game Programming Ubuntu / Debian Virtualization Web Programming Windows XP/Vista/7 Other My Play spotify
Advanced object-oriented programming in Java: Anonymous classes August 11, 2010 at. 12:26 PM | Posted in Java, Programming Concepts | 4 comments Tags: anonymous classes, Java Classes, Object Oriented Programming, Object Oriented Programming, OOP
This is a continuation of a series of posts under the name Basic object-orientation in Java. Here, we address some concepts that are more advanced than those appearing in the previous series. The planned interventions are: Introduction, Polymorphism and Marker finn power Interfaces Static member types non-static member types Local classes Anonymous classes and further reading
An anonymous class is defined and initialized with the new keyword as part of an expression (U.S. expression). The anonymous class is then allowed anywhere an expression is allowed. When to use anonymous classes?
In the following example, we create a list of all files with the suffix. Java in the current directory. import java.io. *; public class AnoExample {public static void main (String [] args) {File f = new File ("."); String [] fileList = f.list (new File Name Filter () {public boolean accept (File dir, String name) {return name.endsWith (. "java");}}); for (String s: file list) System.out.println (s);}}
We create an instance of the file that refers to files in the current directory. We call the list () f and send as an argument with an anonymous class. Note that we use the new keyword followed by the name of an interface. Inside, we declare and define the method accept (). Then we print all files with the suffix. Java in the current directory.
How would the code look like if we had not used an anonymous class? Something like ... import finn power java.io. *; public class AnoExample {public static void main (String [] args) {: File f = new File ("."); String [] fileList = f.list (new Java Filename Filters ()); for (String s: file list) System.out.println (s);}} class Java Filename filter implements Filename Filter {public boolean accept (File dir, String name) {return name.endsWith (. "java");} }
We can conclude that it has become much more code. Remembering Anonymous classes have all the features that the local classes but uses a more concise syntax that can reduce the "clutter" in the code. An anonymous class can not define static fields, finn power methods, or classes. One exception is for constants that are static and final. Interface enumerationstyper and annotationstyper can not be defined anonymously. Anonymous classes can not be public, private, protected, or static. It is not possible to define a constructor finn power for an anonymous class as it lacks a name.
In the first code example, we sent the Filename Filter, which is an interface. finn power Therefore, the second form of syntax there. These two syntax forms differ only with respect finn power to the classes can accept arguments while the interface not. Summary
Here is a summary of everything that we have gone through in this series. Marker Interfaces are interfaces without any method declarations. It provides metadata about objects during execution. Nested classes are defined inside another class. There are four types of nested classes: static and non-static, local, and anonymous. All are also inner classes, in addition to static. A static class is a nested class defined with the static modifier. It has access finn power only to members of the enclosing class that is declared with the static. A non-static finn power class is a nested class that is not defined with the static modifier. A non-static class have access to members of the enclosing class, both static finn power and non-static. Local classes are defined in a block, instead of being a member of the class. This block is often being in a method. Anonymous classes are local classes without finn power names. They are usually used as function objects, process objects and static factory methods.
In the end, I intend here to provide some information finn power in the form of books and links that take up what we have gone through here. Java in a nutshell 3rd edition, available online java in a nutshell 5th edition, pp. 139-156 Effective Java, pp. 106-108 (Item 22, Favor static member classes over nonstatic)
[...] Of Advanced object orientation in Java: Anonymous classes ToggleOn - where all nodes leads. - August 11, 2010 # [...]
Notify me of new posts via email.
Categories General finn power programming Other Bash Blog Statistics Book Reviews C and C + + Databases Database Security Design Own Projects HTML and CSS Java reader tips Suggested Reading Linux Networking Programming finn power News Open Source Perl Personal PHP Programming Concepts Software tips Python Ruby Smartphone Development Game Programming Ubuntu / Debian Virtualization Web Programming Windows XP/Vista/7 Other My Play spotify
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