Accessing a method from within another method

I am having trouble accessing a method from inside a method in the same class.
here is my code:
public String getAns(int ans){
answer = ans;
ranswer = number1 * number2;
if(answer != ranswer){
return "No. Please try again";
}else{
return "Very good!";
genQues();
when i run this i get an Unreachable code error pertaining to genQues();
is this allowed in Java and is there a more practical way to go about this?
Thank you in advance

next time use the correct code tags to post your code.
Think of your problem like this though.
You write
if( something )
then return some value;
else
then return some other value.
The returns end the method here, returning the value.
So, if the method ended at one of these 2 statements, how do you think it'll reach genQues(); ?
Hope this helps.

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No access to method from within the same class

Hey there.
First I have to excuse my English for I'm german and just learning...
Ok, my problem is as follows. I have a class called JDBC_Wrapper it includes the method sendQuery(String query). When I call this method from within another class (where 'wrapper' is my instance of JDBC_Wrapper) it works fine. For example:
wrapper.sendQuery("SELECT * FROM myDataBase");
But then I have written a method called getNumRows() into my JDBC_Wrapper class.
This method should send a query through sendQuery(Strin query) but when calling getNumRows() it says: "java.sql.SQLException: [FileMaker][ODBC FileMaker Pro driver][FileMaker Pro]Unbekannter Fehler." (Unbekannter Fehler -> Unknown Exception). What could that be?
I'm using jdk2 sdk 1.4.2 with BlueJ. My database is Filemaker Pro 6. The ODBC/JDBC connector works fine.
BerndZack

This is within my JDBC_Wrapper class:
public ResultSet sendQuery(String query)
        if(connected)
            try
                Statement s = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
                ResultSet rs = s.executeQuery(query);
                return rs;
            catch(Exception e)
                System.out.println(e);
        else
            //System.out.println("There is no connection to the datasource!");
        return null;
public int getNumRows()
        try
            ResultSet r;
            r = this.sendQuery("SELECT COUNT(*) FROM " + table_name); // At this line the error occurs
            r.next();
            return (int)r.getInt(1);
        catch(Exception e)
            System.out.println(e.getMessage());
            return -1;
}When I call sendQuery() from within another class it works, but calling getNumRows()
throws an exception.

EJB 3.1 @Asynchronous and calling other methods from within

Hey all,
I am helping a friend set up a test framework, and I've turned him on to using JEE6 for the task. I am decently familiar with entity beans, session beans, and such. One of the new features is @Asynchronous, allowing a method to be ran on a separate thread. The test framework generally needs to spawn potentially 1000's of threads to simulate multiple users at once. Originally I was doing this using the Executor classes, but I've since learned that for some reason, spawning your own threads within a JEE container is "not allowed" or bad to do. I honestly don't quite know why this is.. from what I've read the main concern is that the container maintains threads and your own threads could mess up the container somehow. I can only guess that this might be possible if your threads use the container services in some way.. but if anyone could enlighten me on the details as to why this is bad, that would be great.
None the less, EJB 3.1 adds the async capability and I am now looking to use this. From my servlet I use @EJB to access the session bean, and call an async method. My servlet returns right away as it should. From the async method I do some work and using an entity bean store results, so I don't need to return a Future object. In fact, my ejb then makes an HttpClient call to another servlet to notify it that the result is ready.
My main question though, is if it's ok to call other methods from the async method that are not declared @Asynchronous. I presume it is ok, as the @Asynchronous just enables the container to spawn a thread to execute that method in. But I can't dig up any limitations on the code within an async method.. whether or not it has restrictions on the container services, is there anything wrong with using HttpClient to make a request from the method.. and making calls to helper methods within the bean that are not async.
Thanks.

851827 wrote:
Hey all,.. from what I've read the main concern is that the container maintains threads and your own threads could mess up the container somehow. I can only guess that this might be possible if your threads use the container services in some way.. but if anyone could enlighten me on the details as to why this is bad, that would be great.
Yes since the EE spec delegated thread management to conatiners, the container might assume that some info is available in the thread context that you may not have made available to your threads.
Also threading is a technical implementation detail and the drive with the EE spec is that you should concentrate on business requirements and let the container do the plumbing part.
If you were managing your own threads spawned from EJBs, you'd have to be managing your EJBs' lifecycle as well. This would just add to more plumbing code by the developer and typically requires writting platform specific routines which the containers already do anyway.
>
None the less, EJB 3.1 adds the async capability and I am now looking to use this. From my servlet I use @EJB to access the session bean, and call an async method. My servlet returns right away as it should. From the async method I do some work and using an entity bean store results, so I don't need to return a Future object. In fact, my ejb then makes an HttpClient call to another servlet to notify it that the result is ready.
My main question though, is if it's ok to call other methods from the async method that are not declared @Asynchronous. I presume it is ok, as the @Asynchronous just enables the container to spawn a thread to execute that method in. But I can't dig up any limitations on the code within an async method.. whether or not it has restrictions on the container services, is there anything wrong with using HttpClient to make a request from the method.. and making calls to helper methods within the bean that are not async.
Thanks.If you want to be asynchronous without caring about a return value then just use MDBs.
The async methods have no restrictions on container services and there is nothing wrong with calling other non async methods. Once the async method is reached those annotations don't matter anyway (unless if you call thhose methods from a new reference of the EJB that you look up) as they only make sense in a client context.
Why do you need to make the call to the servlet from the EJB? Makes it difficult to know who is the client here. Better use the Future objects and let the initial caller delegate to the other client components as needed.

How to call methods from within run()

Seems like this must be a common question, but I cannot for the life of me, find the appropriate topic. So apologies ahead of time if this is a repeat.
I have code like the following:
public class MainClass implements Runnable {
public static void main(String args[]) {
Thread t = new Thread(new MainClass());
t.start();
public void run() {
if (condition)
doSomethingIntensive();
else
doSomethingElseIntensive();
System.out.println("I want this to print ONLY AFTER the method call finishes, but I'm printed before either 'Intensive' method call completes.");
private void doSomethingIntensive() {
System.out.println("I'm never printed because run() ends before execution gets here.");
return;
private void doSomethingElseIntensive() {
System.out.println("I'm never printed because run() ends before execution gets here.");
return;
}Question: how do you call methods from within run() and still have it be sequential execution? It seems that a method call within run() creates a new thread just for the method. BUT, this isn't true, because the Thread.currentThread().getName() names are the same instead run() and the "intensive" methods. So, it's not like I can pause one until the method completes because they're the same thread! (I've tried this.)
So, moral of the story, is there no breaking down a thread's execution into methods? Does all your thread code have to be within the run() method, even if it's 1000 lines? Seems like this wouldn't be the case, but can't get it to work otherwise.
Thanks all!!!

I (think I) understand the basics.. what I'm confused
about is whether the methods are synced on the class
type or a class instance?The short answer is; the instance for non-static methods, and the class for static methods, although it would be more accurate to say against the instance of the Class for static methods.
The locking associated with the "sychronized" keyword is all based around an entity called a "monitor". Whenever a thread wants to enter a synchronized method or block, if it doesn't already "own" the monitor, it will try to take it. If the monitor is owned by another thread, then the current thread will block until the other thread releases the monitor. Once the synchronized block is complete, the monitor is released by the thread that owns it.
So your question boils down to; where does this monitor come from? Every instance of every Object has a monitor associated with it, and any synchronized method or synchonized block is going to take the monitor associated with the instance. The following:
synchronized void myMethod() {...is equivalent to:
void myMethod() {
    synchronized(this) {
...Keep in mind, though, that every Class has an instance too. You can call "this.getClass()" to get that instance, or you can get the instance for a specific class, say String, with "String.class". Whenever you declare a static method as synchronized, or put a synchronized block inside a static method, the monitor taken will be the one associated with the instance of the class in which the method was declared. In other words this:
public class Foo {
    synchronized static void myMethod() {...is equivalent to:
public class Foo{
    static void myMethod() {
      synchronized(Foo.class) {...The problem here is that the instance of the Foo class is being locked. If we declare a subclass of Foo, and then declare a synchronized static method in the subclass, it will lock on the subclass and not on Foo. This is OK, but you have to be aware of it. If you try to declare a static resource of some sort inside Foo, it's best to make it private instead of protected, because subclasses can't really lock on the parent class (well, at least, not without doing something ugly like "synchronized(Foo.class)", which isn't terribly maintainable).
Doing something like "synchronized(this.getClass())" is a really bad idea. Each subclass is going to take a different monitor, so you can have as many threads in your synchronized block as you have subclasses, and I can't think of a time I'd want that.
There's also another, equivalent aproach you can take, if this makes more sense to you:
static final Object lock = new Object();
void myMethod() {
    synchronized(lock) {
      // Stuff in here is synchronized against the lock's monitor
}This will take the monitor of the instance referenced by "lock". Since lock is a static variable, only one thread at a time will be able to get into myMethod(), even if the threads are calling into different instances.

Calling non-static command from within static method

Hello,
I have a static method that reads bytes from serial port, and I want to set a jTextField from within this method. but I get error that says it is not possible to call non static method from a static one. How can it be solved?

ashkan.ekhtiari wrote:
No, MTTjTextField is the name of jTextFiled class instance.You haven't declared any such variable in the class you posted, not to mention that such a variable name violates standard code conventions.
This is and instance of that object actually. You haven't declared any such variable in the class you posted.
the problem is something else. No, it isn't, based on the information you have provided. If you want accurate guidance, don't post misleading information about your problem.
It can not be set from within static method.A question commonly asked on Java forums concerns an error message similar to the following:
non-static variable cannot be referenced from a static context
In Java, static means "something pertaining to an object class". Often, the term class is substituted for static, as in "class method" or "class variable." Non-static, on the other hand, means "something pertaining to an actual instance of an object. Similarly, the term instance is often substituted for non-static, as in "instance method" or "instance variable."
The error comes about because static members (methods, variables, classes, etc.) don't require an instance of the object to be accessed; they belong to the class. But a non-static member belongs to an instance -- an individual object. There's no way in a static context to know which instance's variable to use or method to call. Indeed, there may not be any instances at all! Thus, the compiler happily tells you that you can't access an instance member (non-static) from a class context (static).
Once you understand this concept, you can fix your own problem.
~

How to call a set method from within a constructor

Hello,
I want to be able to call a set method from within a Scanner, to be used as the argument to pass to the Scanner (from a source file). Here's what i tried:
private void openFiles()
        input = new Scanner( setSource );
    and here is the set method:
public String setSource( String in )
        source = in;
        return source;
    }obviously there will be more code in this method but i'm trying to tackle one problem at a time. Thanks in advance..

The "String in" declaration says: "Nobody may ever invoke setSource() without specifying a certain String. The content of the String is known at run-time only."
In no place in your code you say the compiler: "I want the 'in' variable (actually, parameter) of method setSource() to contain the first arg which is passed to the application".
This is exactly the same mechanism allowing you to write "new Scanner" with something inside the two parentheses.

PL/SQL: Executing a procedure from within another procedure

Hello, I'm a newbie and I need help on how to execute procedures from within another procedure. The procedure that I call from within the procedure have return values that I want to check.
I tried: EXECUTE(user_get_forum_info(p_forumid, var_forum_exists, var_forum_access, var_forumname));
but I get the error message:
PLS-00103: Encountered the symbol "USER_GET_FORUM_INFO" when expecting one of the following::= . ( @ % ; immediate
The symbol ":=" was substituted for "USER_GET_FORUM_INFO" to continue.
And when I tried: EXECUTE(user_get_forum_info(p_forumid, var_forum_exists, var_forum_access, var_forumname));
I get the error message:
PLS-00222: no function with name 'USER_GET_FORUM_INFO' exists in this scope
PL/SQL: Statement ignored
The procedure USER_GET_FORUM_INFO exists. (don't understand why it says "no FUNCTION with name", it's a procedure I'm executing)
I'm stuck so thanks for any help...
Below is all the code. I'm using Oracle 9i on RedHat Linux 7.3.
================================================================================
CREATE OR REPLACE PROCEDURE user_forum_requestsaccess (
p_forumid IN NUMBER,
p_requestmessage IN VARCHAR2
AS
var_forumid NUMBER;
var_forum_exists NUMBER;
var_forum_access NUMBER;
request_exists NUMBER;
var_forumname VARCHAR2(30);
FORUM_DOESNT_EXIST EXCEPTION;
FORUM_USER_HAS_ACCESS EXCEPTION;
FORUM_REQUEST_EXIST EXCEPTION;
BEGIN
SELECT SIGN(NVL((SELECT request_id FROM forum.vw_all_forum_requests WHERE forum_id = p_forumid AND db_user = user),0)) INTO request_exists FROM DUAL;
EXECUTE(user_get_forum_info(p_forumid, var_forum_exists, var_forum_access, var_forumname));
IF var_forum_exists = 0 THEN
RAISE FORUM_DOESNT_EXIST;
ELSIF var_forum_access = 1 THEN
RAISE FORUM_USER_HAS_ACCESS;
ELSIF request_exists = 1 THEN
RAISE FORUM_REQUEST_EXIST;
ELSE
INSERT INTO tbl_forum_requests VALUES (SEQ_TBL_FORUM_REQ_REQ_ID.NEXTVAL, SYSDATE, p_requestmessage, p_forumid, user);
INSERT INTO tbl_forum_eventlog VALUES (SEQ_TBL_FORUM_EVNTLOG_EVNT_ID.NEXTVAL,SYSDATE,1,'User ' || user || ' requested access to forum ' || var_forumname || '.', p_forumid,user);
COMMIT;
END IF;
EXCEPTION
WHEN
FORUM_DOESNT_EXIST
THEN RAISE_APPLICATION_ERROR(-20003,'Forum doesnt exist.');
WHEN
FORUM_USER_HAS_ACCESS
THEN RAISE_APPLICATION_ERROR(-20004,'User already have access to this forum.');
WHEN
FORUM_REQUEST_EXIST
THEN RAISE_APPLICATION_ERROR(-20005,'A request to this forum already exist.');
END;
GRANT EXECUTE ON user_forum_requestsaccess TO forum_user;
================================================================================
Regards Goran

you don't have to use execute when you want to execute a procedure (only on sql*plus, you would use it)
just give the name of the funtion
create or replace procedure test
as
begin
    dbms_output.put_line('this is the procedure test');
end test;
create or replace procedure call_test
as
begin
    dbms_output.put_line('this is the procedure call_test going to execute the procedure test');
    test;
end call_test;
begin
    dbms_output.put_line('this is an anonymous block calling the procedure call_test');
    call_test;
end;
/

Calling a method from a static method

hello all,
I'm calling a non-static method from a static method (from the main method). To overcome this i can make the method i am calling static but is there another way to get this to work without making the method that is being called static?
all replies welcome, thanks

When you call a non-static method, you are saying you are calling a method on an object. The object is an instance of the class in which the method is defined. It is a non-static method, because the instance holds data in it's instance variables that is needed to perform the method. Therefore to call this kind of method, you need to get (or create an instance of the class. Assuming the two methods are in the same class, you could do
public class Foo
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            f.callNonStaticMethod();
}for instance.

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In my case I am building a web service that should run in the tomcat server. When it initialises, it should register with the register, and also be able to search for other web services.
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was told to execute, but using GetTickCount calls shows that its code
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> It seems that an event fired from within another event does not
> actually execute its code until the firing event completes. The fired
> event's Time value in its Event Data Node indicates the time that it
> was told to execute, but using GetTickCount calls shows that its code
> does not execute until the firing event is finished. This happens
> whether Value Signaling is used to generate a Value Change event or if
> CreateUserEvent and GenerateUserEvent is used. Is this because events
> are placed in a queue ? This behavior is different from Delphi for
> example where the fired event executes right away when called from the
> firing event (before the firing event completes).
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Window
s OS has two ways of firing events, Send and Post. The LV events
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by a node, not by a callback. The node you are calling is in the middle
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> I have an event that executes upon a button value change. I would
> like that same event's code to execute when another button is pressed,
> but also have other code in the second button's event execute after
> that first button's event's code completes. Is there another way to
> accomplish this ?
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Yes am using CS4. Have saved it as CS3 now. Ok the file is somewhat complicated and what I am testing is not what I ultimately want to do but if I can pass that variable I can figure it out. In terms of describing the file I think the only parts of importance are what I put in my previous post (please let me know if there is something I should be telling you that I have missed). I am 99.9% sure that I am using the correct instance name.
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Accessing a method from within another method

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