Understanding method implementation for LinkedList class

Hello
I'm new to java and just trying to get my head around data structures, particularly ArrayList and LinkedList implementations. I've looked at the Sun API for both classes, but would like to see how the methods are implmented so I can venture into writing my own versions of these classes..
Does anyone know if there is a resource showing the full method implementation so I can view how they work?
thanks,

a really strange licence: look but don't touch, and it's still under copyrightThis license seems to make sense: you can look at it and learn from it but you are not supposed to make an own, incomptabile version.

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Methods Implemented in Other Classes

Dear all,
In our system I found such a class. In t-code SE24, some of its method names are displayed in blue fonds, instead of ordinary black fonds. When I double click on the method names, a pop-up window indicates "Method xxx is implemented in class yyy". I have no idea about the relationship between the original class and the class yyy. Can anybody explain such a situation?
Thanks + Best Regards
Jerome

Hello Jerome
If you display class CL_GUI_ALV_GRID in transaction SE80 and open the folder "Methods" you will see which method will be displayed in "blue":
- all methods in sub-folder <b>Inherited Methods</b> are shown in blue
- some of these inherited methods have been redefined within the class (folder Redfinitions) and are displayed in "ordinary" black font
Which is the superclass of CL_GUI_ALV_GRID? Simply display the <b>Properties </b>tabstrip of the class. There you see that CL_GUI_ALV_GRID_BASE is the superclass.
Thus, all methods displayed in blue are methods inherited from the superclass that have not been redefined.
Regards
Uwe

Table name for list of methods for given class

Hi Experts,
Is there any table where I can get list of methods in the class?
Req: Input parameter: Class Name
Output: List of all methods in it
Note: As we know, we will have different program names and method names for Classes and Methods. I am okay if I can find table which contains method programs for given class program name.
Regards,
Naveen Inuganti

Hi,
Check table TMDIR.
Thanks,
Venkatesh

Discussion -- Call for answers : Class and Component

Dear all,
1. Component has a clear seperation between the specification and implementation? I can't understand here.The interface define some operations,but eventually we need coding to realize it. Where is the speration?
A class also has methods and coding to realize it. But why we never say a class has a seperation between the specification and implementation?
2. Component has interface; Java has interface. Are they the same idea or different?
Call for answers.
Thanks
Kevin

Hi, Kevin,
First of all, I need to clarify some terminologies and then try to anwser your questions.
(1) Interface only defines operations, but does not specifies how to implement those operations. In Java, abstract class and interface are interfaces. In CORBA, IDL is interface which can be implemented by differenct programming languages.
(2) Java class is both an interface and an implementation, because it not only defines operations, but also implements the operations.
(3) Component provides some specific functionalities, but is not a full-featured application. Usually, a full-featured application consists of many different components. A component can be large or small. A component can be as large as consisting of tens or hundreds of interfaces and classes, like EJB container and server. On the other hand, a component can be as small as comprising only one class; suppose you write a component to calculate foreign currancy conversion.
(4)Specification is a written document that tries to standardize the development of a large component. A specification specififies each party's responsibilities, such as application developers'responsibilities, vendor's responsibilities, administrtor's responsibilities and so on. Also, it specifies the contracts (interfaces) between each party. In doing so, a component can be made very reuseful and can be plug-in and play; changing different vendor's component without breaking application developer's owner code.
In Java world, you see a lot of specifications, such as JDBC, EJB and JMS. When SUN defines those specifications, they use Java interfaces rather other classes to specify interfaces. Here, clear seperation between interface and implementation is very important. (1) If a class is used to specify an interface, SUN must provide implementation for the class. But, the purpose of the specification to allow different vendors to provide implementation.(2) Implementation details can very complex and different vendors may implement the same component very differently. A specification only specifies interfaces but not the implementation. The implementation is up to the vendors. Any implementation is ok as long as they comply to the contracts (interfaces). For instance, one vendor may implement a specified interface using one class and another vendor may implement the same interface using three classes. If a class is used to specify an interface, you restrict vendors' implementation. Usually, in a specification, if you find a class that is used to defines an interface, it means that SUN will provide common implementation for it and vendors do not need to implement it.
In OO design and programing, clearly seperating interfaces from implementations is vital. We should program interface rather than program implementation.
Thanks.
Tommy

Enums with constant-specific method implementation

Just faced the following problem. I have a persistent class with one of the fields of it is enum with constant-specific method implementation:
@Persistent
public class Message
   static public enum Type
       DEFAULT
           @Override
           public String getDescription() { return "Some description"; }
       public abstract String getDescription();
   private Type type;
}When I try to store the record, I get the exception:
java.lang.IllegalArgumentException: Class could not be loaded or is not persistent: messages.Message$Type$1The problem seem to be in that compiler creates a separate class, namely Message$Type$1.class for the DEFAULT instance and this class is not known by BDB..
If I remove the constant-specific method from enum, everything's working fine (as the ..$1.class is not created by compiler).. Except the fact that I'd like to have constant-specific methods there..
Any ideas on this? Maybe it's a bad idea to create constant-specific methods if it means that each constant would get own class file (and they would bloat the storage routines)?

Hi Mikhail,
I recreated the problem here and you're right, constant-specific methods aren't working. This isn't something we thought about, to be honest, or tested.
Just based on an initial quick look I see that for the compiler generated class, the Class.isEnum method returns false, which is why we don't recognize this as an enum and eventually why we throw the exception you're seeing. But assuming that we can identify the class as an enum (that shouldn't be too difficult) I don't know what other problems we will run into in trying to support this.
For now I think the best thing is to avoid using the constant-specific methods. I have opened a ticket (#18357) so that we'll remember to look into this in more detail and see whether it can be supported in the future.
If we are able to support it, then I'm hoping that we won't to store extra metadata for constants that have methods. In other words, I'm hoping that we won't have to add any extra storage or processing overhead.
--mark

Method "equals" not implemented for class "Pan1"

Method "equals" not implemented for class "Pan1" -- this is the error I'm getting while running one static Analyzer. Can anybody say, what is this error , and how to rectify it ?

The static analyzer may have noticed that either you may invoke .equals() on instances of this class (possibly through polymorphism) and you have not implemented the method in your class. This is most likely a warning since many times lack of an implemented .equals() method in such cicumstances will lead to Object.equals() being executed and that simply checks to see if the object references are the same - quite a bit stronger than what one would probably expect from .equals();
it is also possible that you did implement an equals() method but that you used the wrong argument type. This is a common mistake:
public boolean equals(MyClass other) {
return /* something */;
}This type of warning may be ignored, or if it troubles you and there is no way to disable it for the classes that you know you have implemented correctly, you might consider adding an equals method of the form:
public boolean equals(Object other) {
return super.equals(other);
}Chuck

Why the method be implemented in EntityManager.class

package javax.persistence;
public interface EntityManager
     // Methods
     void persist(java.lang.Object p1) { }
     T merge(T p1) { }
     void remove(java.lang.Object p1) { }
     T find(java.lang.Class<T> p1, java.lang.Object p2) { }
     T getReference(java.lang.Class<T> p1, java.lang.Object p2) { }
     void flush() { }
     void setFlushMode(javax.persistence.FlushModeType p1) { }
     javax.persistence.FlushModeType getFlushMode() { }
     void lock(java.lang.Object p1, javax.persistence.LockModeType p2) { }
     void refresh(java.lang.Object p1) { }
     void clear() { }
     boolean contains(java.lang.Object p1) { }
     javax.persistence.Query createQuery(java.lang.String p1) { }
     javax.persistence.Query createNamedQuery(java.lang.String p1) { }
     javax.persistence.Query createNativeQuery(java.lang.String p1) { }
     javax.persistence.Query createNativeQuery(java.lang.String p1, java.lang.Class p2) { }
     javax.persistence.Query createNativeQuery(java.lang.String p1, java.lang.String p2) { }
     void joinTransaction() { }
     java.lang.Object getDelegate() { }
     void close() { }
     boolean isOpen() { }
     javax.persistence.EntityTransaction getTransaction() { }
}

This is the first time I saw this usage. I understood it now, but I was afraid I missed some important concepts on "interface as parameter in the constructor". Therefore, I am wondering where I can find some online document about it in order to understand the usage clearly.
For example, if there are a few method implementations of interface TreeModel in MyDataModel.java, which methods will it call after calling JTree constructor? all methods or only part of them?
Thanks

Change value of GV_MAXROWS for method GET_DATA for class CL_THTMLB_F4HELP

Hi Friends,
I am working on the F4 help of a custom field on the WebUI screen.
I have implemented the GET_V method of the context node attribute and it is working fine, and displaying the results in the F4 help. However, I need to filter these values. So, I have created a Searchhelp exit.
The issue is while filtering in Search help exit, the record_tab[] is filled with only first 500 entries. For this I have manually changed the value of CALLCONTROL-MAXRECORDS = '99999' and it fetches all the existing records in GUI and the filtering works fine. But the same logic doesn't work for Web UI screen. The reason for this is, from Web UI, the class CL_THTMLB_F4HELP is called. In this the method GET_DATA is used to fetch the records. Here there is a field gv_maxrows that is by default '500'. Now, in debugging if i change this to '99999', it works fine. So, how can I do this in coding. How can I change the value of gv_maxrows of the method GET_DATA of the class CL_THTMLB_F4HELP. Can I do this in GET_V method or in the Search Help exit.
Your response will be appreciated.
Thanks & Regards,
Raju.

Hi!
I think that I was not clear in my requirement actually i need to add the document to a folder in a product catalog. So the document is stil not there.
please suggest to get the folder info where the document needs to be attached.
Thanks
Mayank

Getting cl_abap_structdescr for method parameters of LOCAL classes?

Hi guys
I have a bit of a of a problem with getting an instance of the cl_abap_structdescr class for a method parameter type of a local class. The RTTI structure abap_parmdescr can only be used to diffrentiate between the basic built-in ABAP types and whether types are structures, tables or references. The question now arrives that once you have diffentiated that the parameter is a structure how do you determine the actual structure TYPE name for local classes to create an instance of the cl_abap_structdescr to continue your run-time analysis. For dictionary classes the parameter type name can be retrieved from the seosubcodf table, to me it looks as if one would have to resort to scanning the source code of local classes to arrive at the actual structure type name, but before I go to THAT kind of trouble I was wondering whether somebody out there might have a better solution for me. Your help would be grreatly appreciated and rewarded ;).
Kind regards
Ettienne Hugo

Hello Uwe
Thanks for your reply, I checked out the CL_OO_LOCAL_CLASSES class, unfortunately the class actually operates on the local classes declared for a dictionary class. I think to clarify my question I should point out that the parameters I'm trying to process are parameters that belong to classes that are defined and implemented using include programs, these include programs would then typically be used in Function Groups to construct applications so the classes that I refer to are actually not in any way related to dictionary classes. The cl_abap_classdescr class works fine on these types of classes when you refer to them using the "\PROGRAM=my_program\CLASS=my_class" format with the describe_by_name method, unfortunately the class just does not provide sufficient information for structure type parameters to actually construct them during run-time...
Stay well
Ettienne

Exception "not implemented for class oracle.jdbc.driver.T4CNumberAccessor"

Hello I'm having some troubles dealing with 'java.sql.Date' I'm working with express edition database and I have three classes(different packages)
1.Mapper
2.Objects Class
3.ConsoleTest
I need to get an arraylist of objects, some of which contain dates, but when try to do it I get this exception
"java.sql.SQLException: Invalid column type: getDate not implemented for class oracle.jdbc.driver.T4CNumberAccessor"
Do you have any idea how I can implement the getDate method for this T4CNumberAccessor
Here are the methods that I'm using
1.Mapper
public ArrayList<Object> getAllTaskAuctions(Connection con)
          ArrayList<Object> l1 = new ArrayList<Object>();
          String SQLString1 = "select * from taskauction natural join tasks";
PreparedStatement statement=null;
try
//=== get taskauctions natural join tasks
statement = con.prepareStatement(SQLString1);
ResultSet rs = statement.executeQuery();
while(rs.next())
l1.add(new TaskAuction(rs.getInt(1), rs.getInt(2), rs.getInt(3),
rs.getDate(4), rs.getDate(5), rs.getInt(6)));
l1.add(new Task(rs.getInt(1), rs.getInt(2), rs.getString(3),
rs.getString(4), rs.getString(5), rs.getString(6), rs.getInt(7)));
catch (Exception exc)
System.out.println("Fail in TaskAuctionMapper - getAllTaskAuctions");
System.out.println(exc);
return l1;
2.ConsoleTest class
Connection con;
     public Connection getConnection(){
          try{
     Class.forName("oracle.jdbc.driver.OracleDriver");
     con = DriverManager.getConnection(
     "jdbc:oracle:thin:@localhost:1521:XE", "Project", "123" );
     //username/password@[/]host[:port][service_name]
     catch (Exception e)
     {   System.out.println("fail in getConnection()");
     System.out.println(e); }
          return con;
     public static void main(String[] args) {
          ConsoleTest ct = new ConsoleTest();
          TaskAuctionMapper tam1 = new TaskAuctionMapper();
ArrayList<Object> alt1 = tam1.getAllTaskAuctions(ct.getConnection());
Iterator<Object> itr1 = alt1.iterator();
while (itr1.hasNext())
TaskAuction taskauct = (TaskAuction) itr1.next();
//Problem, exception traced to TaskAuctionMapper
System.out.println(
          "Task ID: " + taskauct.getTaskid()+ ", "+
          "StartDate: "+ taskauct.getStartdate()+", "+
          "User ID: " + taskauct.getUserid());
     }

Found the answer, I shouldn't use integers as parameters of column index in the result set, but instead use String to mark the fields :)

Where is the getString() implementation for RS and Object class question

Dear all,
I had these two questions ringing since a long time.
1)ResultSet is an interface.
In my jdbc code I have generally written rs.getString() and rs.getInt etc.. without giving a second thought as to where exactly is this getter implemented !
I have RTF API .. without too much help.
Could some one kindly explain Where is the implementation of the getString method ?
2) Could you please tell why the Wait() Notify() and NotifyAll methods have been implemented in the Object class ? What was the need to define em in the Object class ?
Thanks in advance for your time spent on this.
Rgds

Sarvananda wrote:
In the MySQL driver for example it's implemented in com.mysql.jdbc.ResultSet Right. Now it makes sense to me. Every single db that gives me a driver will have their specific implementation for the interface methods of ResultSet.
>
why do you need that?
..Thats a design decision
One of my friends asked me this and I was caught unawares. Any ideas on what factors could have made this design decision ?
Rgds
>
In the MySQL driver for example it's implemented in com.mysql.jdbc.ResultSet Right. Now it makes sense to me. Every single db that gives me a driver will have their specific implementation for the interface methods of ResultSet.
>
why do you need that?
..Thats a design decision
One of my friends asked me this and I was caught unawares. Any ideas on what factors could have made this design decision ?
A desire to not have to couple your code to a particular database and JDBC driver. It's a classic example of the abstract factory pattern

How to implement the String class "split()" method (JDK1.4) in JDK 1.3

is it possible , with some code, to implement the split() method of the String class......which is added in JDK1.4 ..... in JDK1.3
would be helpful if anyone could suggest some code for this...

Here it is
public static String[] split(String source, char separ){
answer=new Vector();
int position=-1, newPosition;
while ((newPosition=source.indexOf(separ,position+1))>=0){
answer.add(source.subString(position+1,newPosition));
position=newPosition;
} //while
answer.add(source.subString(position+1,source.length-1);
return (String[])(answer.toArray());
} //split

Class implementation for interface

Hello,
I am a beginner in ABAP Objects.
In the coding of method if_swf_ifs_workitem_exit~event_raised of class CL_SWF_UTL_EXIT_NEW
There is the instruction follow :
*Get the workflow container
irh_container ?= im_workitem_context-> get_wf_container()
Im_workitem_context is interface type "IF_WAPI_WORKITEM_CONTEXT"
If I execute in debug mode I see the implemtation class of this interface (im_workitem_context) is "CL_SWF_RUN_WORKITEM_CONTEXT"
But where this information of implementation is defined ? (I saw nothing)
Regards
Christine
Edited by: chris_75 on Sep 7, 2010 4:22 PM

Interfaces allow to implement highly scalable object oriented applications.
Interface is a kind of a template for a real class which forces this class to implement methods defined in an interface.
The main characteristics of an interfaces are:
- they DO NOT contain any implementations (so there is nothing like INTERFACE ... IMPLEMENTATION - they have only DEFINITIONS - implementations are within classes)
- they have only PUBLIC sections.
Why we need an interface. The answer is simple:
We want to handle some objects uniformly from one application compotent, whereas these objects may behave differently inside.
Example:
Let's say we need to build a sorting program for numbers.
The program would have an interface variable L_RIF_SORTER of an interface LIF_SORTER. LIF_SORTER has a method definition SORT with an C_TAB changing parameter.
Sorting application would call the sorting algorithm as follows:
L_RIF_SORTER->SORT( CHANGING c_tab = l_tab ).
Now is the main point:
We want to have 2 kinds of sorting algorithms implemented, let's say BUBBLE SORT and QUICK SORT.
To do so, we implement 2 classes: LCL_BUBBLE_SORT and LCL_QUICK_SORT.
Both classes implement interface using the statment INTERFACES in a public section.
The user would have to choose the algorithm from an input field. Depending on the content of this field the sorting application would instantiate one class or the other using the statement:
CREATE OBJECT l_rif_sorter TYPE (variable_with_class_name).
THis is the point where ABAP gets to know the real object and its type behind the interface.
This approach is generally called the STRATEGY PATTERN. See Wikipedia for this.
I hope I answered your question.
Regards,

Implementation of the hasProperties() method of the Node class

The following snippet of code prints:
false
true
which seems to be a bug.
TextField nameField = new TextField();
System.out.println(nameField.hasProperties());
ObservableMap<Object, Object> props = nameField.getProperties();
System.out.println(nameField.hasProperties());The implementation of the hasProperties() method in the Node class returns true, if the ObservableMap object for storing properties has been created. That is not what is expected from this method. I think, this method should also check if the ObservableMap has any properties.
Can someone confirm that it is a bug?
Thanks
Kishori

You can log it at http://javafx-jira.kenai.com and then, if the developers want to keep it the way it is (which they may for API compatibility purposes), they can at least document it so that a user would know what to expect without writing a test or making a potentially invalid assumption.

Javadoc for private classes methods

I know the Javadoc tool is primarily used for documenting a public API.
Is it considered bad style ever to use it for internal documentation.... description of what private methods are for, why they were selected, etc. It seems like that could be useful too.
Thanks for any thoughts,
John

Hi,
As stated above, javadoc will not be generated for private methods if you don't use that switch. But that's not what I want to say...
javadoc should be used to document what a method does, and the expected arguments etc. It should not say how it solves it's problem (with a few exceptions, e.g. a sorting algorithm can state if it is stable or not, and best/wors case scenarios and execution times).
So I have adopted to some thins I saw a very long time ago, but I can't remember where. I usually document code in the following format.
* Javadoc
* Documentation of the method, arguments, etc.
/* Impl note:
* A note about how the method is implemented / a short note
* about things one have to think about etc.
public void method() {
}So I use both javadoc and implementation comments. (But implementation comments are only used if a method is complex or hard to understand)
/Kaj

Understanding method implementation for LinkedList class

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