Definitions of Object,String etc classes

How/Where can I find definitions of all implicite classes that are included/imported directly for each java files?
Like I want to find definition of Object, String, Integer etc Classes
Thanks
Prasad

What do you mean by "definition"? If you want the documentation, then look at [the API|http://java.sun.com/javase/6/docs/api/]. The classes you mentioned are all in the java.lang package.
If you want their source code, then take a look in the src.zip that should have come with your JDK.

Similar Messages

Converting String to an Object of a class

Hi all,
I want to convert a string to an object of a class.
Please see my below code:
MyClass rahul = null;
String data = "DATA";
rahul = (MyClass) data;
I am getting the error: Invalid cast from java.lang.String to MyClass
Please help me as its urgent

There is no magical String deserialization in java. If your class can convert it's state to a string, then you will need to write the reverse parsing code, presumably using either a constructor which takes a string, or a static method similar to how numbers are handled, like:
MyClass c = MyClass.valueOf(data);Obviously, in either case you will need to write the code to do this.

How do i create objects of ordinary Classes from a javabean

I want to create a class Person below that I want to create an object from in my javabeans.
Look below Person class definition for continuation.
package data;
public class Person
private String name;
public Person()
name = "No name yet.";
public Person(String initialName)
name = initialName;
public void setName(String newName)
name = newName;
public String getName()
return name;
public void writeOutput()
System.out.println("Name: " + name);
public boolean sameName(Person otherPerson)
return (this.name.equalsIgnoreCase(otherPerson.name));
I run this bean class in the WEB-INF/classes/data folder creating a Person object in the deal() method below
When I compile the class it seems to fail. It does not recognise the Person class. Can you help me with a description of what to do to call
ordinary class objects from javabean class definitions.
What directories should the simple classes be put and what should I include in the javabean to be able to access them?
package data;
import java.sql.*;
import data.*;
public class Bean
{ private Connection databaseConnection ;
// private Person p;
public Bean()
super();
public boolean connect() throws ClassNotFoundException, SQLException
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
String sourceURL = "jdbc:odbc:robjsp";
databaseConnection = DriverManager.getConnection(sourceURL);
return true;
public ResultSet execquery(String restrict) throws SQLException
Statement statement = databaseConnection.createStatement();
String full = "SELECT customerid,CITY,Address from customers " + restrict;
ResultSet authorNames = statement.executeQuery(full);
return (authorNames ==null ) ? null : authorNames;
public String deal() throws SQLException
{ Person p = new Person();
p.setName("Roberto");
return p.getName();
}

There is no "Copy File" function in Lightroom.
Lightroom was designed to eliminate the need to make duplicate copies of files. The organizational tools in Lightroom allow you to have one file categorized in many ways, you can assign multiple keywords to the photos (for example: Winery, Finger Lakes, Fall Foliage, Jessica). Similarly, you can have a file categorized in multiple Lightroom collections at the same time, all without making a copy of the photo. The benefit of this is that you don't need to make multiple copies of each photo, one copy suffices, and thus disk space is saved; and furthermore if you should edit a photo or add metadata, you only need to do this once, and the photo's appearance, or the photo's metadata is changed, and visible to you no matter how you choose to access the photo (pick any keyword or any collection and you will see the change)

Create Object of "ObjectName" Class by giving only Domain Name.

Hie,
I want to create Object of "ObjectName" class without specifying its key value properties, but i want to only specify the domain name.
For eg:
ObjectName on=new ObjectName("jboss.ws4ee:*"); here jboss.ws4ee is the domain name and after colon(:) will come the key value properties.. i dont want to specify that because i want the list of all mbeans coming under this domain i.e. jboss.ws4ee
So anyone can plzzz help me..
Regards.

Hi,
What were you trying to do with that name?
ObjectName on=new ObjectName("jboss.ws4ee:*");
You cannot create an MBean with such an ObjectName. You can only
use it as first argument to queryNames() and queryMBeans();
If you want to get the attributes of all jboss MBeans then you will need to
do something like that:
final ObjectName pattern=new ObjectName("jboss.ws4ee:*");
for (ObjectName o : server.queryNames(pattern,null)) {
    System.out.println("MBean: " + o);
    for (MBeanAttributeInfo info : server.getMBeanInfo(o).getAttributes()) {
         final String attrname = info.getName();
         System.out.println("\t"+attrname+"="+server.getAttribute(o,attrname));
}(disclaimer: this code was eyed-compiled)
hope this helps,
-- daniel
JMX, SNMP, Java, etc...
http://blogs.sun.com/jmxetc

Cannot convert type class java.lang.String to class oracle.jbo.domain.Clob

Cannot convert type class java.lang.String to class oracle.jbo.domain.ClobDomain.
Using ADF Business Components I have a JSFF page fragment with an ADF form based on a table with has a column of type CLOB. The data is retrieved from the database and displayed correctly but when any field is changed and submitted the above error occurs. I have just used the drag and drop technique to create the ADF form with a submit button, am I missing a step?
I am using the production release of Jdeveloper11G

Reproduced and filed bug# 7487124
The workaround is to add a custom converter class to your ViewController project like this
package oow2008.view;
import javax.faces.application.FacesMessage;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.convert.Converter;
import javax.faces.convert.ConverterException;
import oracle.jbo.domain.ClobDomain;
import oracle.jbo.domain.DataCreationException;
public class ClobConverter implements Converter {
     public Object getAsObject(FacesContext facesContext,
                               UIComponent uIComponent,
                               String string) {
       try {
         return string != null ? new ClobDomain(string) : null;
       } catch (DataCreationException dce) {
         dce.setAppendCodes(false);
         FacesMessage fm =
           new FacesMessage(FacesMessage.SEVERITY_ERROR,
                            "Invalid Clob Value",
                            dce.getMessage());
         throw new ConverterException(fm);
     public String getAsString(FacesContext facesContext,
                               UIComponent uIComponent,
                               Object object) {
       return object != null ?
              object.toString() :
              null;
}then to register the converter in faces-config.xml like this
<faces-config version="1.2" xmlns="http://java.sun.com/xml/ns/javaee">
<application>
    <default-render-kit-id>oracle.adf.rich</default-render-kit-id>
</application>
<converter>
    <converter-id>clobConverter</converter-id>
    <converter-class>oow2008.view.ClobConverter</converter-class>
</converter>
</faces-config>then reference this converter in the field for the ClobDomain value like this
          <af:inputText value="#{bindings.Description.inputValue}"
                        label="#{bindings.Description.hints.label}"
                        required="#{bindings.Description.hints.mandatory}"
                        columns="40"
                        maximumLength="#{bindings.Description.hints.precision}"
                        shortDesc="#{bindings.Description.hints.tooltip}"
                        wrap="soft" rows="10">
            <f:validator binding="#{bindings.Description.validator}"/>
            <f:converter converterId="clobConverter"/>
          </af:inputText>

Accessing the same object from multiple classes.

For the life of me I can't workout how I can access things from classes that haven't created them.
I don't want to have to use "new" multiple times in seperate classes as that would erase manipulated values.
I want to be able to access and manipulate an array of objects from multiple classes without resetting the array object values. How do I create a new object then be able to use it from all classes rather than re-creating it?
Also I need my GUI to recognize the changes my buttons are making to data and reload itself so they show up.
All help is good help!
regards,
Luke Grainger

As long as you have a headquarters it shouldn't be to painfull. You simply keep a refrence to your ShipDataBase and Arsenal and all your irrellevant stuff in Headquarters. So the start of your Headquarters class would look something like:
public class Headquarters{
public Arsenal arsenal;
public ShipDatabase db;
//constructor
public Headquarters(){
    arsenal = new Arsenal(this, ....);
    db = new ShipDatabase(...);
//The Arsenal class:
public class Arsenal{
public Headquarter hq;
public Arsenal(Headquarter hq, ....){
    this.hq = hq;
    .Then in your ShipDatabase you should, as good programing goes, keep the arraylist as a private class variable, and then make simple public methods to access it. Methods like getShipList(), addToShipList(Ship ship)....
So when you want to add a ship from arsenal you write:
hq.db.addToShipList(ship);
.Or you could of course use a more direct refrence:
ShipDatabase db = hq.db;
or even
ShipList = hq.db.getShipList();
but this requires that the shiplist in the DB is kept public....
Hope it was comprehensive enough, and that I answered what you where wondering.
Sjur
PS: Initialise the array is what you do right here:
//constructor
shipList = new Ship[6];
shipList[0] = new Ship("Sentry", 15, 10, "Scout");
" " " "etc
shipList[5] = new Ship("Sentry", 15, 10, "Scout");PPS: To make code snippets etc. more readable please read this article:
http://forum.java.sun.com/faq.jsp#messageformat

How to cast an object to a class known only at runtime

I have a HashMap with key as a class name and value as the instance of that class. When I do a 'get' on it with the class name as the key, what I get back is a generic java.lang.Object. I want to cast this generic object to the class to which it belongs. But I don't know the class at compile time. It would be available only at runtime. And I need to invoke methods on the instance of this specifc class.
I'm not aware of the ways to do it. Could anybody suggest/guide me how to do it? I would really appreciate.
Thanks a lot in advance.

Thanks all for the prompt replies. I am using
reflection and so a generic object is fine, I guess.
But a general question (curiosity) specific to your
comment - extraordinarily generic...
I understand there's definitely some overhead of
reflection. So is it advisable to go for interface
instead of reflection?
Thanks.Arguments for interfaces rather than reflection...
Major benefit at run-time:
Invoking a method using reflection takes more than 20 times as long without using a JIT compiler (using the -Xint option of Java 1.3.0 on WinNT)... Unable to tell with the JIT compiler, since the method used for testing was simple enough to inline - which resulted in an unrealistic 100x speed difference.
The above tests do not include the overhead of exception handling, nor for locating the method to be executed - ie, in both the simple method invocation and reflective method invocations, the exact method was known at compile time and so there is no "locative" logic in these timings.
Major benefit at compile-time:
Compile-time type safety! If you are looking for a method doSomething, and you typo it to doSoemthing, if you are using direct method invocation this will be identified at compile time. If you are using reflection, it will compile successfully and throw a MethodNotFoundException at run time.
Similarly, direct method invocation offers compile-time checking of arguments, result types and expected exceptions, which all need to be dealt with at runtime if using reflection.
Personal and professional recommendation:
If there is any common theme to the objects you're storing in your hashtable, wrap that into an interface that defines a clear way to access expected functionality. This leaves implementations of the interface (The objects you will store in the hashtable) to map the interface methods to the required functionality implementation, in whatever manner they deem appropriate (Hopefully efficiently :-)
If this is feasible, you will find it will produce a result that performs better and is more maintainable. If the interface is designed well, it should also be just as extensible as if you used reflection.

Casting base class object to derived class object

interface myinterface
     void fun1();
class Base implements myinterface
     public void fun1()
class Derived extends Base
public class File1
     public myinterface fun()
          return (myinterface) new Base();
     public static void main(String args[])
          File1 obj = new File1();
          Derived dobj = (Derived)obj.fun();
Giving the exception ClassCastException......
Can't we convert from base class object to derived class.
Can any one help me please...
Thnaks in Advance
Bharath kumar.

When posting code, please use tags
The object returned by File1.fun() is of type Base. You cannot cast an object to something it isn't - in this case, Base isn't Dervied. If you added some member variables to Derived, and the compiler allowed your cast from Base to Derived to succeed, where would these member variables come from?
Also, you don't need the cast to myinterface in File1.fun()
Also, normal Java coding conventions recommend naming classes and interfaces (in this case, myinterface) with leading capital letters, and camel-case caps throughout (e.g. MyInterface)

Why can't I create new object from a class that is in my big class?

I mean:
class A
B x = new B;
class B
and how can I solve it if I still want to create an object from B class.
Thank you very much :)

public class ItWorksNow {
public ItWorksNow() {
public static void main ( String[] argv ) throws Exception {
ItWorksNow.DaInnaClass id = new ItWorksNow().new DaInnaClass();
public class DaInnaClass {
}

Get session object in a class

hi,
is possible obtain the session object in a class method without send it from jsp as a parameter?

you mean like this?
     public ActionForward execute(
          ActionMapping mapping,
          ActionForm form,
          HttpServletRequest req,
          HttpServletResponse res)
          throws Exception {
          SessionManager sm = new SessionManager(req);
                                ....sessionmanager class
package com....;
import java.util.*;
import java.lang.reflect.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.jsp.*;
import javax.servlet.http.*;
import org.apache.log4j.*;
* <code>SessionManager</code> is a wrapper for request, response and session
* @author
public class SessionManager {
     static Logger log = Logger.getLogger(SessionManager.class);
     ** Holds string containing the unique identifier assigned to this session
     private String sessionid;
     ** Holds HttpSession object
     private HttpSession session;
     ** Holds request object object - must be passed in by the calling application
     private HttpServletRequest request;
     ** Holds response object - any application sending a response must call
     ** session manager
     private HttpServletResponse response;
     ** Holds Servlet Context - useful if logging is reqd.
     private ServletContext context;
      * Page context.
     private PageContext pctx = null;
     ** Constructor to initialize with a request object
     public SessionManager(HttpServletRequest req) {
          request = req;
          session = req.getSession();
          sessionid = session.getId();
     ** Constructor to initialize with a pagecontext object - convenient to call from jsp's
     public SessionManager(PageContext pctx) {
          request = (HttpServletRequest) pctx.getRequest();
          response = (HttpServletResponse) pctx.getResponse();
          context = pctx.getServletContext();
          session = pctx.getSession();
          sessionid = session.getId();
          this.pctx = pctx;
     ** Constructor to initialize with request, response objects
     public SessionManager(HttpServletRequest req, HttpServletResponse resp) {
          request = req;
          response = resp;
          session = req.getSession();
          sessionid = session.getId();
     ** Constructor to initialize with request, servletcontext objects
     public SessionManager(HttpServletRequest req, ServletContext ctx) {
          request = req;
          context = ctx;
          session = req.getSession();
          sessionid = session.getId();
     ** Constructor to initialize with request, response and context objects
     public SessionManager(HttpServletRequest req, HttpServletResponse resp, ServletContext ctx) {
          request = req;
          response = resp;
          context = ctx;
          session = req.getSession();
          sessionid = session.getId();
     ** Setter and getter methods
     public void setRequest(HttpServletRequest req) {
          request = req;
          session = req.getSession();
          sessionid = session.getId();
     ** Setter and getter methods
     public void setContext(ServletContext ctx) {
          context = ctx;
     ** Setter and getter methods
     public ServletContext getContext() {
          return context;
     public void createLoginSession(java.io.Serializable obj) {
          if (obj == null)
               log.debug("Object is null");
          setAttribute("user", obj);
     public void setAttribute(String key, java.io.Serializable obj) {
          session.setAttribute(key, obj);
     public void removeAttribute(String key) {
          session.removeAttribute(key);
     ** Setter and getter methods
     public HttpServletRequest getRequest() {
          return request;
     ** Setter and getter methods
     public HttpServletResponse getResponse() {
          return response;
     ** Checks if either member session or guest session exists
     public boolean isLoggedIn() {
          if (session.getAttribute("user") != null)
               return true;
          else
               return false;
     public long getCreationTime() {
          return session.getCreationTime();
     ** Setter and getter methods
     public String getId() {
          return session.getId();
     public long getLastAccessedTime() {
          return session.getLastAccessedTime();
     public int getMaxInactiveInterval() {
          return session.getMaxInactiveInterval();
     ** Setter and getter methods - also useful for retrieving state object(s)
     public Object getAttribute(String name) {
          if (session != null)
               Object sObject = session.getAttribute(name);
               //Log.debug("Session State for the object "+name+" is "+sObject);
               return sObject;
          else
               return null;
     ** Setter and getter methods - gets enum of all stored state objects
     public Enumeration getAttributeNames() {
          return session.getAttributeNames();
     public void invalidate() {
          session.invalidate();
          // Remove all object that is bound to this session
          //wip : Resetting instance variable.
          //This is necesary as further operations on session will
          //result in illegalstateexception
          session = null;
     public boolean isNew() {
          return session.isNew();
     public void setMaxInactiveInterval(int interval) {
          session.setMaxInactiveInterval(interval);
      * This method returns the host url in the form "www.carclub.com".
      * <p>
      * The return value is compatible with default_website field of clubs DB table.
      * </p>
      * @return host url present as part of the http request object
     public String getHostURL()
          if (request == null)
               return null;//No request object present, hence return null
          String str = request.getServerName();
          //Log.debug("--- The request URL is --- " + str);
          return str;
      * Flushes <code>out</code> stream.
     public void flush()
          throws IOException
          if (pctx != null)
               pctx.getOut().flush();
}

Instantiating an object of a class using variable

Can anyone please tell me how to instantiate an object of a class, the class name is stored in string variable.
something like:
String s = "MyClass";
<s> anObj = new <s> ;
what will be the appropriate substitution of <s> ?

Orkay, Leave it up to u to learn the Exceptions that are gonna be thrown. Look up the APIs, Rather easy
String s = <fullyQualifiedClassName>;
try {
Class someClass = Class.forName(s);
Object instance = someClass.newInstance();
if (instance instanceof <someExpectedInstance>) {
<someExpectedInstance> x = (<someExpectedInstance>) instance;
} catch (Exception e) {
System.err.println(e.getMessage());
}Primarily look up the reflection API, and in particular Class.

Referencing fields between objects of same class

Say I have created multiple TicketMachines from this class. Is there a way I create a method that uses "System.out.println" that would print the price of another TicketMachine object. And if so, could you please point me in the direction to find out how.
* TicketMachine models a naive ticket machine that issues
* flat-fare tickets.
* The price of a ticket is specified via the constructor.
* It is a naive machine in the sense that it trusts its users
* to insert enough money before trying to print a ticket.
* It also assumes that users enter sensible amounts.
* @author David J. Barnes and Michael Kolling
* @version 2006.03.30
public class TicketMachine
    // The price of a ticket from this machine.
    private int price;
    // The amount of money entered by a customer so far.
    private int balance;
    // The total amount of money collected by this machine.
    private int total;
    //Creates a machine that issues tickets at a default price of 1000.
    public TicketMachine( )
     //Exercise 2.39 & 2.42(continues below)
      * By removing the parameter from this constructer
      * and setting the value of price to 1000, objects
      * from this class are automatically constructed with
      * a ticket price of 1000.
        price = 1000;
        balance = 0;
        total = 0;
    //Exercise 2.42
     * Create a machine that issues tickets of the given price.
     * Note that the price must be greater than zero, and there
     * are no checks to ensure this.
    public TicketMachine(int thePrice)
        price = thePrice;
        balance = 0;
        total = 0;
     * Return the price of a ticket.
    public int getPrice()
        return price;
     * Return the amount of money already inserted for the
     * next ticket.
    public int getBalance()
        return balance;
     * Receive an amount of money in cents from a customer.
    public void insertMoney(int amount)
        balance = balance + amount;
     * Print a ticket.
     * Update the total collected and
     * reduce the balance to zero.
    public void printTicket()
        // Simulate the printing of a ticket.
        System.out.println("##################");
        System.out.println("# The BlueJ Line");
        System.out.println("# Ticket");
        System.out.println("# " + price + " cents.");
        System.out.println("##################");
        System.out.println();
        // Update the total collected with the balance.
        total = total + balance;
        // Clear the balance.
        balance = 0;
    //Exercise 2.33
    //Prints "Please insert the correct amount of money." to the text terminal.
    public void prompt()
        System.out.println("Please insert the correct amount of money.");
    //Exercise 2.34
    //Displays the value of the price field in the text terminal.
    public void showPrice()
        System.out.println("The price of a ticket is " + price + " cents.");
    //Exercise 2.35
     * After creating two ticket machines with different prices
     * and calling thier showPrice methods it showed a different
     * output for each instance. This effect happenes because the
     * showPrice method prints out a string and the value of the price
     * field, which happens to be different in each instance, thereby
     * printing a different output.
    //Exercise 2.36
     * The result of System.out.println("# " + "price" + " cents.");
     * would print the string "# price cents." to the text terminal.
    //Exercise 2.37
     * The result of System.out.println("# price cents.");
     * would be the same as the result of exercise 2.36.
    //Exercise 2.40
    //This method is a mutator and takes no parameters
    //Empties the money form the ticket machine
    public void empty()
        total = 0;
    //Exercise 2.41
    //This method is a mutator
    //Changes the price of a ticket
    public void setPrice(int newPrice)
        price = newPrice;
}

Objects can refer to fields in other objects of the same class.
It's not clear from your description what you're trying to accomplish, however.

How to create an object of a class?

plz read the question carefully ..
how to create the object of a class by giving the class name as an String
suppose i have a java file name:" java1.java ".
so now how to create an object of this class "java1"by passing a string "java1"..

kajbj wrote:
rajeev-usendi wrote:
thanks but still i have problem..
i have created the object but now i m unable to do anything with that created object..
i have coded like this..
Object o= Class.forName("java1").new Instance();
after this i m unable to do anything with the object 'o'..So why did you create the instance? You can also get all methods using reflection, but that is probably not what you want to do. You should instead let the class implement an interface and cast the created object into that interface ans call the methods that you want to call.
KajI agree with Kaj. If you need to use a class that's unavailable at compile time, you should create an appropriate interface by which to refer to the class and then you create instances reflectively and access them normally via their interface (which is called reflective instantiation with interface access)

How to create object by getting class name as input

hi
i need to create object for the existing classes by getting class name as input from the user at run time.
how can i do it.
for exapmle ExpnEvaluation is a class, i will get this class name as input and store it in a string
String classname = "ExpnEvaluation";
now how can i create object for the class ExpnEvaluation by using the string classname in which the class name is storted
Thanks in advance

i think we have to cast it, can u help me how to cast
the obj to the classname that i get as inputThat's exactly the point why you shouldn't be doing this. You can't have a dynamic cast at compile time already. It doesn't make sense. Which is also the reason why class.forName().newInstance() is a very nice but also often very useless tool, unless the classes loaded all share a mutual interface.

How to make an object of inner class and use it ?

Hi tecs,
In my JSF application i have a need to make an inner member class in one of my bean class.
How can i make the object of this class?(what should be the entry in faces-config)
And there are text box and check box (in the JSP) associated with the elements of this inner class. What should be the coding in JSP so that elements in the JSP can be linked with the corresponding members of the inner class ?
Plz help.
Thnx in advance.

Hi
I am havin 10 text boxes in my application.
But out of 10 , 3 will be always together(existence of one is not possible without the other two.)
Now i want to create a vector of objects ( here object will consist of the value corresponding to these three boxes),there can be many elements in this vector.
So i m thinking to make an inner class which have three String variables corresponding to these text boxes that exists together.
What can b done ?

Definitions of Object,String etc classes

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