Local instance variables

I'm trying to develop an AIR app that will require login before usage. The login will be handled through an ajax request.
However, this means I'd like to store some local variables, that must only be available for the instance opened, so whenever that instance is closed I need to variables to dissapear. Also no sharing must happen between instances, even by the same user on the same machine.
Are there any variables of this type available ?
Or can I use the database or cryptstore in a fashion where it won't be shared at all, and will be deleted on shutdown of the app ?

Or you could do your own homework.

Similar Messages

How to change value of instance variable and local variable at run time?

As we can change value at run time using debug mode of Eclipse. I want to do this by using a standalone prgram from where I can change the value of a variable at runtime.
Suppose I have a class, say employee like -
class employee {
public String name;
employee(String name){
this.name = name;
public int showSalary(){
int salary = 10000;
return salary;
public String showName()
return name;
i want to change the value of instance variable "name" and local variable "salary" from a stand alone program?
My standalone program will not use employee class; i mean not creating any instance or extending it. This is being used by any other calss in project.
Can someone tell me how to change these value?
Please help
Regards,
Sujeet Sharma

This is the tutorial You should interest in. According to 'name' field of the class, it's value can be change with reflection. I'm not sure if local variable ('salary') can be changed - rather not.

Instance variable to hold the element of a tag in the xml file

Hi I have an xml file that is handled using this parser
<attr id="MY_NAME" >
this parser hanled the above tag but now I want to have it handle
<attr id="MY_NAME" desc="GOOD">
but I need to create an instance variable to handle the desc element in the attr tag .
Can some one help me out as this is not my file and I am having trouble to do please......
import java.util.*;
import java.io.*;
import javax.xml.parsers.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
   The SupportMatrix class provides static variables and methods to simplify
   the determination of whether or not a given attribute is supported for a
   certain object type (queue manager, channel, etc.), depending on the version
   and platform of the queue manager to which it belongs.
   The SupportMatrix class may not be instantiated. Its constructor is private.
   An instance of the class is created internally in the static initializer so
   that the XML parsing methods are available.
   A corresponding XML document, SupportMatrix.xml, is parsed to create the various
   HashMaps which contain the version/platform dependency information. A number of
   inner classes are used to represent the various elements of the XML matrix
   definition.
   Here's a sample document:
   
   <supportmatrix>
     
     <object classid="1">
       
       <version cmdlevel="base">
         
         <attr id="MQCA_Q_MGR_NAME">
           
           <support platforms="UNIX,WINDOWS,OS400,VMS,NSK" maxlen="48" type="MQCFST"/>
           <support platforms="MVS" maxlen="4" type="MQCFST"/>
         </attr>
         <attr id="MQCA_Q_MGR_DESC">
           
           <support platforms="all" maxlen="64" type="MQCFST"/>
         </attr>
         
         <attr id="MQIA_PLATFORM"/>
         <attr id="MQIA_COMMAND_LEVEL"/>
       </version>
       
       <version cmdlevel="520" include="base">
       </version>
     </object>
   </supportmatrix>
   The inner classes, and their hierarchical relationships are as follows:
     SupportObject - corresponds to the <object> element. Stored in a static HashMap, and
                     keyed by classid.
       VersionObject - corresponds to the <version> element. Stored in a HashMap instance
                       variable of the SupportObject class, keyed by cmdlevel.
         AttributeObject - corresponds to the <attr> element. Stored in a HashMap instance
                           variable of the VersionObject class, keyed by attribute name.
           PlatformObject - corresponds to the <support> element. Stored in HashMaps belonging
                            to the AttributeObjects, keyed by platform. A single PlatformObject
                            instance is created when the support tag is encountered. The
                            "platforms" attribute of the support element is then processed. For
                            each platform in the comma-delimited list, an entry is added to the
                            collection of PlatformObjects. This is to greatly simplify later
                            lookups.
   In order to support the 'include' feature of object and version elements, certain
   functions are recursive. If the attribute to be validated is not found for the passed
   cmdlevel, the 'parent' VersionObject is consulted by means of the 'include' value. If
   the chain of VersionObjects has been exhausted and the attribute in question has still not
   been located, the next SupportObject in the chain is consulted in a similar fashion.
public class SupportMatrix extends DefaultHandler {
    /** The objects collection holds all the SupportObjects, keyed by classid. */
    private static HashMap objects;
    /** xmlFile will name the xml document to be parsed. Note that using the
        default class loader expects the string to be the path to the file. It must
        NOT begin with the '/' character. */
    private static String xmlFile =
        ResourceManager.getApplicationProperties().getProperty("SupportMatrixFile");
    private Stack stack;
    /** This static initializer allocates the static objects collection, creates an
        instance of the SupportMatrix class for xml parsing purposes, and initiates
        the parse operation to populate the collection. */
    static {
        objects = new HashMap();
        // Create a parser and process the xml doc
        SupportMatrix handler = new SupportMatrix();
        InputSource is = null;
        try {
            is = new InputSource(ClassLoader.getSystemClassLoader().getResourceAsStream(xmlFile));
            XMLReader xmlReader =
                SAXParserFactory.newInstance().newSAXParser().getXMLReader();
            xmlReader.setFeature("http://xml.org/sax/features/namespaces", true);
            xmlReader.setContentHandler(handler);
            if (is == null) {
                System.err.println("No input stream, dammit");
            xmlReader.parse(is);
        } catch(Exception e) {
            e.printStackTrace();
    /** Private constuctor, used only for XML parsing. */
    private SupportMatrix() {
        stack = new Stack();
    /** Add a SupportObject instance to the objects collection. */
    private void addObject(SupportObject obj) {
        String key = obj.getClassId();
        objects.put(key, obj);
    /* DefaultHandler methods                                              */
    /** Not used. */
    public void characters(char[] ch, int start, int length) {}
    /** Not used. */
    public void endDocument() {}
    /** For the version, object, and attr elements, pop the top element of the stack. */
    public void endElement(String uri, String localName, String qName) {
        if (localName.equals("version") || localName.equals("object") || localName.equals("attr")) {
            stack.pop();
    /** Not used. */
    public void setDocumentLocator(Locator locator) {}
    /** Not used. */
    public void startDocument() {}
    /** Most of the work is done here. Create the appropriate inner class instance for
        element; for object, version, and attr, push the element onto the stack so that
        child elements may be added to their collections as needed. */
    public void startElement(String uri, String localName, String qName,
                             Attributes attributes) {
        String include = attributes.getValue("include");
        if (localName.equals("object")) {
            SupportObject obj = new SupportObject(attributes.getValue("classid"), include);
            addObject(obj);
            stack.push(obj);
        } else if ( localName.equals("version")) {
            VersionObject ver = new VersionObject(attributes.getValue("cmdlevel"), include);
            ((SupportObject)stack.peek()).addVersion(ver);
            stack.push(ver);
        } else if ( localName.equals("attr")) {
            AttributeObject a = new AttributeObject(attributes.getValue("id"));
            //String desc = StringFactory.getString(attributes.getValue("desc"));
            //if(desc != null)
               //     a.setAttribute();
            String readonly = attributes.getValue("readonly");
            String exclude = attributes.getValue("exclude");
            if (include != null && exclude != null) {
                Log.log(Log.ERROR, this, "include and exclude are mutually exclusive, exclude value ignored");
                exclude = null;
            if (include != null) {
                a.setCondition(include, true);
            if (exclude != null) {
                a.setCondition(exclude, false);
            if (readonly != null)
                a.setReadonly(readonly.equals("y"));
            ((VersionObject)stack.peek()).addAttr(a);
            stack.push(a);
        } else if (localName.equals("support")) {
            String platforms = attributes.getValue("platforms");
            String readonly = attributes.getValue("readonly");
            String maxlen = attributes.getValue("maxlen");
            String type = attributes.getValue("type");
            int attrType = 0;
            if (type != null) {
                if (type.equals("MQCFIN")) {
                    attrType = CMQCFC.MQCFT_INTEGER;
                } else if (type.equals("MQCFIL")) {
                    attrType = CMQCFC.MQCFT_INTEGER_LIST;
                } else if (type.equals("MQCFST")) {
                    attrType = CMQCFC.MQCFT_STRING;
                } else if (type.equals("MQCFSL")) {
                    attrType = CMQCFC.MQCFT_STRING_LIST;
                } else if (type.equals("EXBIN")) {
                    attrType = MqcConstants.EXCFT_BINARY;
                } else if (type.equals("EXPCF")) {
                    attrType = MqcConstants.EXCFT_PCF;
            PlatformObject p = null;
            if (readonly == null) {
                p = new PlatformObject(platforms);
            } else {
                p = new PlatformObject(platforms, readonly.equals("y"));
            String exclude = attributes.getValue("exclude");
            if (include != null && exclude != null) {
                Log.log(Log.ERROR, this, "include and exclude are mutually exclusive, exclude value ignored");
                exclude = null;
            if (include != null)
                p.setCondition(include, true);
            if (exclude != null)
                p.setCondition(exclude, false);
            if (attrType != 0)
                p.setType(attrType);
            if (maxlen != null)
                p.setLen(Integer.parseInt(maxlen));
            ((AttributeObject)stack.peek()).addPlatform(p);
    public static boolean isExported(int attribute, TopologyModelNode node) {
        String name = ResourceManager.getAttributeName(attribute);
        return isExported(name, node);
    public static boolean isExported(String attribute, TopologyModelNode node) {
        // Find the qmgr node to fetch platform and cmdlevel
        TopologyModelNode qmgr = node.getModel().getQMgrNode(node.getAddress());
        // If there's no qmgr for this node, it must be one of 'ours'.
        if (qmgr == null)
            return false;     // None of 'our' objects can be exported to MQSC.
        String classId = node.getClassId();
        String cmdLevel = qmgr.getAttributeValue("MQIA_COMMAND_LEVEL");
        String platform = qmgr.getAttributeValue("MQIA_PLATFORM");
        return isExported(attribute, classId, cmdLevel, platform, node);
    public static boolean isExported(int attribute, String classId, String cmdLevel, String platform,
                                     TopologyModelNode node) {
        String name = ResourceManager.getAttributeName(attribute);
        return isExported(name, classId, cmdLevel, platform, node);
    /** Determine if an attribute is exportable. The attribute name, the classid of the object to
        which it belongs, plus the command level and platform of the queue manager are all needed
        to make this determination.
        Start by finding the AttributeObject for the combination of attribute, classid, and
        command level. If we can't find the AttributeObject, we assume that the attribute
        is not exported. Otherwise, find out if it is exportable for the selected platform.
    public static boolean isExported(String attribute, String classId, String cmdLevel, String platform,
                                     TopologyModelNode node) {
        AttributeObject attr = getAttributeObject(attribute, classId, cmdLevel);
        if (attr == null) {
            return false;
        } else {
            return attr.isExported(platform, node);
    public static boolean isSupported(int attribute, TopologyModelNode node) {
        String name = ResourceManager.getAttributeName(attribute);
        return isSupported(name, node);
    public static boolean isSupported(String attribute, TopologyModelNode node) {
        // Find the qmgr node to fetch platform and cmdlevel
        TopologyModelNode qmgr = node.getModel().getQMgrNode(node.getAddress());
        // If there's no qmgr for this node, it must be one of 'ours'.
        if (qmgr == null)
            return true;
        String classId = node.getClassId();
        String cmdLevel = qmgr.getAttributeValue("MQIA_COMMAND_LEVEL");
        String platform = qmgr.getAttributeValue("MQIA_PLATFORM");
        return isSupported(attribute, classId, cmdLevel, platform);
    public static boolean isSupported(int attribute, String classId, String cmdLevel, String platform) {
        String name = ResourceManager.getAttributeName(attribute);
        return isSupported(name, classId, cmdLevel, platform);
    /** Determine if an attribute is supported. The attribute name, the classid of the object to
        which it belongs, plus the command level and platform of the queue manager are all needed
        to make this determination.
        Start by finding the SupportObject for the classid. If it isn't there, we make the assumption
        (for now) that the attribute is supported. The only classids for which this can occur are
        broker, agent, and the various container objects.
        Propagate the isSupported request to the chain of SupportObjects (based on 'include' values)
        until we get a 'true' result or we run out of SupportObjects. */
    public static boolean isSupported(String attribute, String classId, String cmdLevel, String platform) {
        if (attribute == null)
            return false;
        SupportObject obj = (SupportObject)objects.get(classId);
        // If the object type isn't even in the support matrix, we interpret that to
        // mean that it's a Broker or Agent, in which case all attributes are supported
        // at present.
        if (obj == null)
            return true;
        boolean result = false;
        while (result == false && obj != null) {
            result = obj.isSupported(attribute, cmdLevel, platform);
            if (result == false && obj.getInclude() != null) {
                obj = (SupportObject)objects.get(obj.getInclude());
            } else
                obj = null;
        return result;
    /** Locate an AttributeObject for a given attribute name, object type, and command level.
        This is a helper function for the getMaxLen and getType methods. */
    private static AttributeObject getAttributeObject(String attr, String classID, String cmdLevel) {
        AttributeObject result = null;
        SupportObject obj = (SupportObject)objects.get(classID);
        while (result == null && obj != null) {
            result = obj.getAttr(attr, cmdLevel);
            if (result == null && obj.getInclude() != null) {
                obj = (SupportObject)objects.get(obj.getInclude());
            } else
                obj = null;
        return result;
    /** Determine the maximum length for a given combintation of attribute name, object type,
        command level, and platform. If the AttributeObject can't be found, or if the length
        hasn't been set, return -1. */
    public static int getMaxLen(String attr, String classId, String cmdLevel, String platform) {
        AttributeObject a = getAttributeObject(attr, classId, cmdLevel);
        if (a == null)
            return -1;
        return a.getMaxLen(platform);
    /** Determine the PCF parm type for a given combintation of attribute name, object type,
        command level, and platform. If the AttributeObject can't be found, or if the length
        hasn't been set, return -1. */
    public static int getType(String attr, String classId, String cmdLevel, String platform) {
        AttributeObject a = getAttributeObject(attr, classId, cmdLevel);
        if (a == null)
            return -1;
        return a.getType(platform);
    /** Inner class to contain platform-specific info for an attribute. */
    class PlatformObject {
        /** This instance variable will contain the comma-delimited string of all
            platforms to which this object applies. */
        private String platform;
        private int maxlen;
        private String condition = null;
        private boolean include;
        private boolean readonly;
        private boolean lenSet;
        private int attrType;
        private boolean typeSet;
        public PlatformObject(String p, boolean readonly) {
            platform = p;
            this.readonly = readonly;
            lenSet = false;
            typeSet = false;
        public PlatformObject(String p) {
            this(p, false);
        public void setCondition(String condition, boolean include) {
            this.condition = condition;
            this.include = include;
        public boolean isReadonly() {
            return readonly;
        public boolean isExported(TopologyModelNode node) {
            if (condition != null) {
                boolean test = false;
                try {
                    test = Utilities.evaluateCondition(node, condition);
                } catch (Exception e) {}
                if (include ^ test)
                    return false;
            return !readonly;
        public void setLen(int len) {
            maxlen = len;
            lenSet = true;
        public void setType(int type) {
            attrType = type;
            typeSet = true;
        public String getPlatform() {
            return platform;
        public int getMaxLen() {
            if (!lenSet)
                return -1;
            return maxlen;
        public int getType() {
            if (!typeSet)
                return -1;
            return attrType;
    /** This class represents a specific MQSeries attribute. It can optionally contain
        instances of the PlatformObject class as needed. When the 'platforms' collection
        is empty, the attribute is supported on all platforms. It is also possible to
        include a PlatformObject for the 'all' platform, if specific attribute characteristics
        need representation. When the 'platforms' collection is non-empty, it will include one
        entry for each platform where the attribute is supported. */
    class AttributeObject {
        private String attribute;
        private String attrValue;
        private HashMap platforms;
        private String condition = null;
        private boolean include;
        private boolean readonly = false;
        public AttributeObject(String a) {
            this(a, false);
        public AttributeObject(String a, boolean readonly) {
            attribute = a;
            platforms = new HashMap();
            this.readonly = readonly;
        public void setCondition(String condition, boolean include) {
            this.condition = condition;
            this.include = include;
        public void setReadonly(boolean readonly) {
            this.readonly = readonly;
        public boolean isReadonly() {
            return readonly;
        public void addPlatform(PlatformObject p) {
            for (StringTokenizer st = new StringTokenizer(p.getPlatform(), ","); st.hasMoreTokens() ;) {
                platforms.put(st.nextToken(), p);
        public PlatformObject getPlatform(String platform) {
            PlatformObject p = (PlatformObject)platforms.get(platform);
            if (p == null)
                p = (PlatformObject)platforms.get("all");
            return p;
        public String getAttribute() {
            return attribute;
        public int getMaxLen(String platform) {
            PlatformObject p = getPlatform(platform);
            if (p == null)
                return -1;
            return p.getMaxLen();
        public int getType(String platform) {
            PlatformObject p = getPlatform(platform);
            if (p == null)
                return -1;
            return p.getType();
        public boolean isSupported(String platform) {
            if (platforms.isEmpty()) {
                return true;
            if (platforms.containsKey(platform)) {
                return true;
            if (platforms.containsKey("all")) {
                return true;
            return false;
        public boolean isExported(String platform, TopologyModelNode node) {
            if (readonly) {
                Log.log(Log.DEBUG, this, attribute + " is readonly, returning false");
                return false;
            if (condition != null) {
                Log.log(Log.DEBUG, this, "Testing condition = " + condition);
                boolean test = false;
                try {
                    test = Utilities.evaluateCondition(node, condition);
                    Log.log(Log.DEBUG, this, "Condition result is " + test);
                } catch (Exception e) {
                    Log.log(Log.ERROR, this, "Condition through an exception");
                if (include ^ test)
                    return false;
            if (platforms.isEmpty()) {
                return true;
            PlatformObject p = getPlatform(platform);
            if (p == null) {
                Log.log(Log.DEBUG, this, platform + " not found for " + attribute + ", returning false");
                return false;
            return p.isExported(node);
    /** This class represents a specific value of a queue manager's command level. A
        given instance of this class may 'include' a 'parent' instance through its
        include instance variable. The traversal of the parent/child hierarchy is
        delegated to the SupportObject class, since that is where the collection of
        VersionObjects lives. */
    class VersionObject {
        private String cmdLevel;
        private String include;
        private HashMap attributes;
        public VersionObject(String cmdLevel, String include) {
            this.cmdLevel = cmdLevel;
            this.include = include;
            attributes = new HashMap();
        public void addAttr(AttributeObject attr) {
            attributes.put(attr.getAttribute(), attr);
        public AttributeObject getAttr(String attr) {
            return (AttributeObject)attributes.get(attr);
        public String getCmdLevel() {
            return cmdLevel;
        public String getInclude() {
            return include;
        public boolean isSupported(String attr, String platform) {
            AttributeObject obj = (AttributeObject)attributes.get(attr);
            if (obj == null) {
                return false;
            } else
                return obj.isSupported(platform);
    /** This class represents an MQSeries object type, as identified by its classid, e.g.
        queue manager or local queue. This class implements an include facility similar to
        that described for the VersionObject. The traversal of that hierarchy is delegated
        to the static isSupported method, because the collection of SupportObject instances
        is a static variable of the SupportMatrix class. */
    class SupportObject {
        private String classId;
        private String include;
        private HashMap versions;
        public SupportObject(String classId, String include) {
            this.classId = classId;
            this.include = include;
            versions = new HashMap();
        public void addVersion(VersionObject obj) {
            String key = obj.getCmdLevel();
            versions.put(key, obj);
        public String getClassId() {
            return classId;
        public String getInclude() {
            return include;
        public boolean isSupported(String attr, String cmdLevel, String platform) {
            boolean result = false;
            VersionObject obj = (VersionObject)versions.get(cmdLevel);
            if (obj == null)
                obj = (VersionObject)versions.get("base");
            // I don't actually know what it means if obj is null at this point.
            // It probably can't happen.
            if (obj == null)
                return false;
            while (result == false && obj != null) {
                result = obj.isSupported(attr, platform);
                if (result == false && obj.getInclude() != null) {
                    obj = (VersionObject)versions.get(obj.getInclude());
                } else
                    obj = null;
            return result;
        public AttributeObject getAttr(String attr, String cmdLevel) {
            AttributeObject result = null;
            VersionObject obj = (VersionObject)versions.get(cmdLevel);
            if (obj == null)
                obj = (VersionObject)versions.get("base");
            // I don't actually know what it means if obj is null at this point.
            // It probably can't happen.
            if (obj == null)
                return null;
            while (result == null && obj != null) {
                result = obj.getAttr(attr);
                if (result == null && obj.getInclude() != null)
                    obj = (VersionObject)versions.get(obj.getInclude());
                else
                    obj = null;
            return result;
}

Are you the one who commented out the code you're looking for ?//String desc = StringFactory.getString(attributes.getValue("desc"));You just have to modify you AttributeObject class to hold a new field : String description. And then, it's up to you to create a new constructor or a new setter method.
Btw, this is not a Swing related question.

Null Instance Variables on Screenflow

Hi,
I have some problems with instance variable of type BPM Objects in a Screenflow.
I always create automatic processes without user interaction, and on server side I have seen that it's not necessary to instantiate an instance variable. Moreover if within a method I write (I use the Java style syntax):
String a;
a.toString(); // just to call a method on a not-instantiated variable
everything works correctly, the "a" variable is automatically instantiated.
But it seems that in an automatic activity of a Screenflow it's different, I need to do the new also for Instance Variables.
Then, in the Screenflow I have an Instance Variable myObject of type MyObject that is a BPM Object. This object has an attribute myStrings that is an array of String.
To instantiate the instance variable I can write:
myObject = new MyObject();
But then I get a java.lang.*NullPointerException* when I call the extend method of its attribute myStrings to add a string.
Do you agree with me that on the Screenflow code it's necessary to instantiate the variables?
How can I instantiate an Array of String?
Thank you.

Thanks Daniel, I'm using ALBPM 6.0,
i know the line where I get the exception, I have a logMessage before and after each line of code, and then in the exception stack there is the PBL Method line indicated:
Caused by: java.lang.NullPointerException
at xobject.Fuego__AutoGen__Screenflows__.__ScreenflowConJsp.automatic1(__ScreenflowConJsp.xcdl:*19*)
19 is the code line where I get the exception. In this line I have this:
myObject.myStrings.extend(arg1 : a);
but the null object is not the array, it's myObject that is an Instance Variable.
In ALBPM60_Studio_ReferenceGuide at chapter Programming Styles paragraph Java Programming Style there is:
This style emulates Java syntax and adds several features to match PBL expressions. These added features include:
• Output arguments
• Input and display statements
• Variable auto-initialization
In fact in my previuos BPM projects I have seen that is not necessary to istantiate the variables, both for Instance Variable and local variable declared within a method. In my previous post I did an example:
String a;
a.toString();
Usually this causes an Exception, but not in ALBPM methods.
My main question is: is it possible that this is true just for Server side methods and not for Screenflow methods? Because in my case I need to instantiate every Instance Variable of my Screenflow (for example the myObject instance variable) in an Automatic Activity I have put as first Activity of the flow.
Thanks again for your help.

Doubt about scope of instance variable

Hi All,
i have a doubt about scope of instance variable.
if i declare a instance variable in servlet , i want to know whether it can be shared(means everywhere ) or not.
thanks in advance
Gopal

The servlet container will create one servlet object, and run multiple threads through its service() / doGet() / doPost() methods.
That means that any instance variables of the servlet are shared between multiple requests, and can cause problems with threads accessing the same variable..
To make your servlets thread-safe
1 - have no instance variables - only use local variables in the doGet/doPost method.
2 - use the session scope for storing variables you need over multiple calls.
Cheers,
evnafets

Servlet Instance Variable scope

Just want to clarify my understanding of instance variables in regards to Servlets.
public class TestServlet extends HttpServlet
    public String instVariable = "";
public void processRequest(HttpServletRequest request, HttpServletResponse response)
      instVariable = request.getParameter("param");
      response.sendRedirect( instVariable ) ;
}If two users both enter the processRequest logic at the same time, is it possible that they will both get the same
result? My understanding of this was that if they each execute the first line, then each execute the second
line, each user would be redirected to the same instVariable that was set by the second request.
What would be the easiest way to stop this from happening? syncronized? ThreadSafe?
I just want a simple clarification.
Thanks for the insight.

If two users both enter the processRequest logic at
the same time, is it possible that they will both get
the same
result? My understanding of this was that if they
each execute the first line, then each execute the
second
line, each user would be redirected to the same
instVariable that was set by the second request. Yes, it is possible, since there is only one instVariable.
What would be the easiest way to stop this from
happening? syncronized? ThreadSafe? The easiest way to avoid that is to simply not use an instance variable. Use a local variable, declared within your processRequest method. Each thread (i.e. each user of the servlet) has its own set of local variables.

BufferedReader bf; is this also treated as instance variable?

hi i m just now finished my assignment and doing documentation
and i got a single line here
BufferedReader bf; //instance variable
constructor{
bf = new BufferedReader(new InputStreamReader(System.in));
}and now i m doing documentation suddenly i got confused whether i should
write this as instance variable or not. should i?? or shouldn't i
i think this is obejct,,,,,,,but..i think it is instance variable as well..coz
it is located in the class scope..confusing.....
or not..

hi i m just now finished my assignment and doing
documentation
and i got a single line here
BufferedReader bf; //instance variable
constructor{
bf = new BufferedReader(new
w InputStreamReader(System.in));
}and now i m doing documentation suddenly i got
confused whether i should
write this as instance variable or not. should i?? or
shouldn't i
i think this is obejct,,,,,,,but..i think it is
instance variable as well..coz
it is located in the class scope..confusing.....
or not..Okay, first of all constructor {} isn't valid Java syntax, I'm assuming you just used it for brevity. Second, yes bf is an instance variable because it's not a) static (class-) variable or b) local variable.
If you thought instance variables refer only to primitives (int, byte etc.) you're wrong. Object references can also be instance variables.
So yes, it is both an object reference and an instance variable.
Sincerely,
Jussi

What's the difference between global variables and instance variables?

hi im just a biginner,
but what is the difference between these two?
both i declare them above the constructor right.
and both can access by any method in the class but my teacher said
global variables are not permitted in java....
but i don't know what that means....and i got started to confuse these two types,,
im confusing.......
and why my teacher said declaring global variables is not permitted,,,,,,
why.....

instance variables are kindof like Global variables. I'm not surprised you are confused.
The difference is not in how they are declared, but rather in how they are used.
There are two different "styles" of programming
- procedural programming.
- object oriented programming.
Global variables are a term from Procedural programming.
In this style of programming, you have only one class, and one "main" procedure. You only create one instance of the class, and then "run" it.
There is one thread of control, which goes through various methods/procedures to accomplish your task.
In this style of programming instance variables ARE "global" variables. They are accessible to all methods. There is only one instance of the class, and thus only one instance of the variables.
Global variables are "bad" BECAUSE you can change them in any method you like. Even from places that shouldn't have to. Also if you use the same name as a global variable and a local variable, you can cause great trouble. This can lead to very subtle bugs, as the procedures interact in ways you don't expect.
The preferred method in procedural programming is to pass the values as parameters to the methods, and only refer to the parameters, and local variables. This means that you can track exactly what your method is doing, and what it affects. It makes it simpler to understand. If you use global variables in your methods, it becomes harder to understand.
So when are instance variables not global variables?
When you are actually using the class as an Object, rather than just a program to run. If you are creating multiple instances of an object, all with different values for their instance variables, then they are not global variables. For instance you declare a Person object with an attribute "firstname". Your "main" program then creates many instances of the Person object, each with their own "firstname"
I guess at the end of all this, it comes down to definitions.
Certainly you can write procedural code in java. You can treat your instance variables, for all intents and purposes like global variables.
I can only think to show a sort of example
public class Test1
   User[] users;
   public void printUsers(){
     // loop through and print all the users
     // uses a global variable
      for(int i=0; i<users.length; i++){
        users.printUser();
public void printUsers(User[] users){
// preferred method - pass it the info it needs to do the job
for(int i=0; i<users.length; i++){
users[i].printUser();
public Test1(){
User u1 = new User("Tom", 20);
User u2 = new User("Dick", 42);
User u3 = new User("Harry", 69);
users = new User[3];
users[0] = u1;
users[1] = u2;
users[2] = u3;
printUsers();
printUsers(users);
public static void main(String[] args)
new Test1();
class User{
String firstName;
int age;
public User(String name, int age){
this.firstName = name;
this.age = age;
public void printUser(){
// here they are used as instance variables and not global variables
System.out.println(firstName + " Age: " + age);
Shit thats a lot of typing, and I'm not even sure I've explained it any good.
Hope you can make some sense out of this drivel.
Cheers,
evnafets

Parsing XML and Storing values in instance variable

hi,
i'm new to XML.
here i'm trying to parse an XML and store their element data to the instance variable.
in my main method i'm tried to print the instance variable. but it shows "" (ie it print nothing ).
i know the reason, its becas of the the endElement() event generated and it invokes the characters() and assigns "" to the instance variable.
my main perspective is to store the element data in instance variable.
thanks in advance.
praks
import java.io.*;
import java.net.*;
import java.util.*;
import javax.xml.parsers.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
public class mysax extends DefaultHandler
     String ctelement;
     CharArrayWriter contents;
     String vname1,vrcbreg1,vaddress1,vcountry1,vtelephone1,vfax1;
     String vname,vrcbreg,vaddress,vcountry,vtelephone,vfax;
     public mysax()
          vname1 = null;
          vrcbreg1 = null;
          vaddress1 = null;
          vcountry1 = null;
          vtelephone1 = null;
          vfax1 = null;
          contents= new CharArrayWriter();
     public void doparse(String url) throws Exception
          SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp = spf.newSAXParser();
ParserAdapter pa = new ParserAdapter(sp.getParser());
pa.setContentHandler(this);
pa.parse(url);
     public void startElement(String namespace,String localName,String qName,Attributes atts)
          ctelement = localName;
     public void endElement(String uri,String localName,String qName) throws SAXException
     public void characters(char[] ch,int start, int length) throws SAXException
          try
               if(ctelement.equals("name"))
                    vname = new String (ch,start,length);
                    System.out.println("The method "+vname1);
          }catch (Exception e)
               System.out.println("The exception "+e);
     public static void main(String args[])
          try
          mysax ms = new mysax();
          ms.doparse(args[0]);
          System.out.println("the contents name "+ms.vname1);
          catch(Exception e)
               System.out.println("this is exception at main" +e);
my XML looks like
<coyprofile_result>
<company>
<name>abcTech</name>
<rcbreg>123456789</rcbreg>
<address>Singapore</address>
<country>sg</country>
<telephone>123456</telephone>
<fax>123155</fax>
</company>
</coyprofile_result>

I believe that the problem has to do with the value you assign to ctelement. You are assigning the value of localName to ctElement, however for the element: <name>...</name> the localname is empty string i.e. "", but qName equals "name". Because you are assigning empty string to ctElement, when you do the comparison in characters of ctElement to "name" it will always be false. So in startElement change it to ctElement = qName; Try it and see if it works. I have produced similar programs and it works for me.
Hope this helps.

How to use an BPM Instance Variable in JSP page

Hi All,
I am using the JSP Presentation, but i don't know how to use an Instance variable in JSP page, that instance already declared in the process. And Can u explain the syntax that to include the JS file into jsp page
Regards
Vasu.
Edited by bpmvasu at 04/03/2007 10:43 PM

Hi Mariano,
I'm using JSP presentation too. In "Interactive Component Call" active i'm using "Use JSP presentation", but i only can define one instance variable, i need to add more instance variables. In "Advanced" option of this task, i have the argument mapping .. but i don't understand how to use it.
I have a instance variable called "genders" of the type String[Int] (Associative Array) and i'm mapping this instance variable in "Arguments Show In" option of the advanced option of JSP presentation. In JSP presentation i have the code:
<select <f:fieldName att="person.gender"/>>
               <c:forEach var="gender" begin="0" items="${genders}" varStatus="status">
                    <c:choose>
                         <c:when test="${person.gender == gender}">
                              <option value="<c:out value="${gender}"/>" selected="true"><c:out value="${gender}"/></option>
                         </c:when>
                         <c:otherwise>
                              <option value="<c:out value="${gender}"/>"><c:out value="${gender}"/></option>
                         </c:otherwise>
                    </c:choose>
               </c:forEach>
          </select>And in my screenflow i have the code:
genders[0] = "Male"
genders[1] = "Female"But when i run my application, i have the error: "The task could not be successfully executed. Reason: 'java.lang.ClassCastException: java.lang.Integer'."
What's the problem?

Trying to create a local instance of the remote object

Hi,
I have a ClassA on which I need to be able to invoke RMI calls. Problem is the interface which ClassA implements does not throw exceptions. To get around this problem I have created a wrapper class ClassWrap which has a ClassA attribute and calls made to ClassWrap are directed to this ClassA object. A facade type design I think it's called.
ClassWrap implements Remote so it can be used as a Remote object.
When I create an instance of ClassWrap and deploy it on a server, my client has no problem communicating with the remote ClassWrap object via a remote stub ClassWrap_Stub.
Problem is I also want my client to be able to use a local instance of ClassWrap. Whan I try to create an instance of ClassWrap in my client I get a remote Exception ... but !! when I have a ClassWrap_Stub object in my classpath then there is no problem creating a ClassWrap object.
Any ideas why this happens?

What you are trying to do should work just fine. Do you have the wrapper class file in your client jar?

Report Painter - Use of Constants / Local Formula Variable

Hi,
I am using constant and/or local formula variable in report painter in FSI.
I could use both the values for calculating percentages, ie. it can be used for multiplication or division. However, when I try to use it for addition or subtraction, I am getting the error message no. KH206.
In all cases, I am using different values in the formula, i.e. a absolute figure and a GL based figure.
I am not able to understand, why it even allows me for calculating percentage.
Can anyone help me in using a absolute figure for input and thereafter use it in addition / subtraction.
I would prefer an immediate solution to this as I am in the final stages of this report.
Full points guaranteed.....

Hi Kash,
Thanks for your reply..
Can you elaborate bit further. You mean to say I should create a Constant with some value.
Thereafter how should I bring that in the form. But, How do I enter the Constant in the Formula... There is no key for entering any text in the formula.. there are only ID (the values which we bring in the form and which can be selected for the formula) and numbers which can be entered.
So how do I enter the name of the Constant?
I tried just keying in the name of the Constant, and I could check the formula also, However, while saving the form, I am getting an error,
Element WCaplimit Bis letztem ATag bis &$BISD is not defined correctly -> check definition
Message no. KH206
Diagnosis
In element WCaplimit Bis letztem ATag bis &$BISD the system adds quantities and values or different currencies.
Can you please revert back with step by step solution?
Appreciate your prompt reply.... Thanks

How can I use evaluate to get the instance variable in customized tag

1.
At first , I create a class called bean,and declared several params in it and do not define any getter function for the param.
class bean{
String param = "test";
SomeClass scObj = new SomeClass();
2.
The second ,I use
request.setAttribute("beanObj",new bean());
3.
And then I wanna use the customized tag to show a text box , then initialize it's value.
<salt:text name="param" value="beanObj.param">
<salt:text name="obj" value="beanObj.scObj.func()">
4.
I tried the evaluator provided by JexlContext ,Struts, JSTL and it seems that if I do not define the getter for the variable ,I can not get the bean's instance variable's value.
Expression e = ExpressionFactory.createExpression( value );
JexlContext jc = JexlHelper.createContext();
jc.getVars().put(strInitBeanName, request.getAttribute("beanObj"));
Object obj = e.evaluate(jc);
the result of the obj is null....
Can anybody recommand some other evaluator can get the value of a instance variable from an object?

do you have any other suggestion ? Nops, somebody else may have though. AFAIK, all lookups of the type
beanName.propertyNameuse reflection on the getXXX() methods to access the property.
Having said that, I guess you could write one though in a custom tag, using the same - reflection (you will ahve to rely on the java.lang.reflect.Field class quite heavily) - but that would be reinventing the wheel for most other functionality that you would have to include (like looking up the bean in scope etc)
cheers,
ram.

Not able to access parent instance variable in outside of methods in child

Hi,
I am not getting why i am not able to access parent class instance variable outside the child class intance methods.
class Parent
     int a;
class Child extends Parent
     a = 1; // Here i am getting a compilation error that Syntax error on token "a", VariableDeclaratorId expected after this token
     void someMethod()
          a = 1; // Here i am not getting any compilation error while accessing parent class variable
}Can any one please let me know exact reason for this and what is the error talks about?
Thanks,
Uday
Edited by: Udaya Shankara Gandhi on Jun 13, 2012 3:30 AM

You can only put assignments or expressions inside methods, constructors or class initializors, or when declaring a variable.
It has nothing to the with Child extending Parent.
class Parent {
    int a = 1;
    { a = 1; }
    public Parent() {
        a = 1;
   public void method() {
       a = 1;
}

Binding: Instance variable loses value.

Hi all,
Just making my first steps into Objective-C, I've done a lot of C, C++ and C# on win & linux. Anyhow, I've been hacking away happily and discovered a peculiar behaviour, and I'm not sure if it's my code or some obscure bug in Xcode.
1. I have a Check Box(NSButton) directly bound to a BOOL instance variable called "checkValue" using KVC. The containing class is a custom NSView subclass.
2. I manually implemented the setter according to KVC naming rules "setCheckValue".
3. When debugging the UI (check box) calls the setter perfectly with the correct value, which shows up in the NSLog output.
4. I hooked up the action for the check box as well, and inside the action handler the instance variable reports the value correctly. Everything looks fine.
5. Now here's the rub. I put a mousedown event handler into the class as well, and it is called flawlessly when I click on the custom view. However, "checkValue" does not report the correctly set value.
So, how can a class instance variable, which is set and reports correctly elsewhere in the same scope, all of the sudden take on a nonsense value in a event handler? If a variable has a value set, it should be the same everywhere within the same scope!
Below is simplified code extracted from the original project for clarity. It produces exactly the same behaviour as the more complex project without the distracting code.
#import "CheckBoxHandler.h"
@implementation CheckBoxHandler
@synthesize checkValue;
//Apparently this is required for binding in NSView based classes
//The same behaviour occurs even if you remove this.
+(void)initialize
[self exposeBinding:@"checkValue"];
-(id)initWithFrame:(NSRect)frameRect
self = [super initWithFrame:frameRect];
if(!self)
return nil;
[self setCheckValue:YES];
return self;
//manual impelementation of KVC setter
-(void)setCheckValue:(BOOL)v
checkValue = v;
NSLog(@"Setter Called: checkValue is %d", checkValue);
//The action works fine as evidenced by Log output
//Check and uncheck the box a few times.
-(IBAction)checkBoxAction:(id)sender
NSLog(@"UI State:%d Ivar State: %d", [checkBox state], checkValue);
//Mouse clicking on the view calls into this event.
//The problem is the value reported by [self checkValue] OR checkValue directly
//do not match the UI state. In fact it always reports some nonsense value.
-(void)mouseDown:(NSEvent *)event
NSLog(@"Inside Mousedown: checkValue is: %d", [self checkValue]);
@end
I have a workaround, but it really bends my head when something doesn't behave as expected!

I have synthesized against "checkValue", although I manually implemented the setter so I could set a breakpoint and observe the value. I thought [self checkValue] and self.checkValue both simply call the same getter, just different syntax.
The setting of the value using the UI checkbox happens outside of the event call chain. I can check and uncheck the checkbox and the value changes correctly. The checkbox is in a separate space on the window, so clicking it does not activate mousedown on the view, this is correct behaviour. Clicking on the view does activate the mousedown event, this is done after I've set the checkbox so the value has been set well before the mousedown event. Thus it should already have the correct value in the event.
For completeness this is the interface file:
#import <Cocoa/Cocoa.h>
@interface CheckBoxHandler : NSView {
IBOutlet NSButton *checkBox;
BOOL checkValue;
-(IBAction)checkBoxAction:(id)sender;
@property (assign, readwrite) BOOL checkValue;
@end
I'll change everything to self.checkValue just for the excercise. Ok, done. checkValue still reports a value of 1 in the mousedown event regardless of the value set elsewhere.

Local instance variables

Similar Messages

Maybe you are looking for