How many objects are created?

I have this question which some one posted to me.
He asked me how many objects are created when an object of a simple class is created for example
class A{
public static void main(String args[])
A a1 = new A();
Now how many objects are created? I think only one. Can anyone tell me if any other objects are also created.
Plz tell me .

No, the answer is indeed 1. All the other objects
(including the String[] in the main method
parameters) are created outside of the A
class, either by the JVM itself or by some other
class that calls the A.main() method. You can try
this out for yourself by adding a constructor such as
A()
System.out.println("Creating class A");
} and see what prints out.Take a closer look at the question:
how many objects are created when an object of a
simple class is created for exampleIt doesn't say "how many objects of type A are created".
I.e. The VM has to load class A before you can create an object from it, and thus an object of type Class is created. There are also a bunch of other objects which needs to be created before you can instantiate A.
Kaj

Similar Messages

How many Objects are created in this?

Hi,
How many objects are created in the flwg code:
String str = new String("Hello");
String str2 = "Hey there";
str = str + str2;

Depends if you're counting objects created at compile time.
"Hello" is created at compile time. That's 1.
new String("Hello") creates a new String object at runtime, pointing its backing array at the "Hello" in the constant pool. That's 2.
"Hey there" is created at compile time. 3.
str + str2 I might do everything at compile time, or it might do some at runtime. I don't know if str is considered a compile time literal here. I think not, but I'm not sure. You can check by using javap. If I'm correct, then at runtime you'll create a StringBuffer (4) and another String (5).
So I'd say 5 objects. But if the compiler treats str as a literal and therefore can do the str+str2 at compile time, then it might do so without creating the StringBuffer. Or it might still create it at compile time, use it, and throw it out.

Garbage Collection: how many objects are created after for loop?

Please see the fallowing java code
1 public class Test1 {
2
3     public static void main(String[] args) {
4
5          MyObj obj = null;
6          for(int i=0;i<5;i++){
7               obj = new MyObj();
8          }
9 // do something
10
11     }
12 }
so my question is How may objects are eligible for garbage collection at line no: 9 (// do something)?

so my question is How may objects are eligible for
garbage collection at line no: 9 (// do something)?It's impossible to answer that question since we don't know how MyObj is implemented.
Kaj

How many String are created?

public String makinStrings() {
     String s = �Fred�;
     s = s + �47�;
     s = s.substring(2, 5);
     s = s.toUpperCase();
     return s.toString();
}How many objects are created when this method is called?
My answer is 5
1. "Fred"
2. "47"
3. "Fred47"
4. "ed4"
5. "ED4"
But my friend is telling it is 3.
1. "Fred"
2. "47"
3. "Fred47"
I know that any method called on String object creates a brand new String. Please help me with the solution whether it is 3 or 5.

hi,
First of all i want to thanks for all of your replies.
My friend is saying that when we say "How many objects when method is invoked" it means at runtime. String literals are not created at run time.
String s = �Fred�; // No object is creatd here
s = s + �47�; // One object created "s"
s = s.substring(2, 5); //Another object "s"
s = s.toUpperCase(); //Another object "s"
return s.toString();
Hence total 3 objects.
Now the i have got a doubt. Are String literals created at Complie time itself. Or since String s = "Fred" is a compile time constant field. And String literal "47" is also a compile time constant field.
Suppose if the code is like this
String s = new String("Fred")
String s1 = s; ---------------- Then is this String object created at Run time.
String s2 = "47" ----------- This object is created at Complie time.
Please clarify my doubt.

How many tables are created in Master data loading ( Including hierchy )

hi ,
Please anybody , can you tell us how many tables are created in Master data loading ( Including hierchy )
thanks
Phani

Hi PP,
Depending upon the definition of an infoobject, the tables are created when the objects are activated.
/BI<C OR DIGIT>/<TABLE CODE><INFOOBJECT>
<C or digit>: C = Customer-defined InfoObjects
digit = SAP-defined InfoObjects
<table code>: S = SID table
T = Text table
P = Time-independent master data attributes
Q = Time-dependent master data attributes
M = Union of time-dependent and time-independent master
data attributes
X = SID table for time-independent navigational attributes
Y = SID table for time-dependent navigational attributes
H = Hierarchy table
K = Hierarchy SID table
I = Hierarchy SID structure table
J = Hierarchy interval table
Thnaks...
Shambhu

How many sessions are created in Server ?

Hi All developers,
SCJP back again.........
Anybody please tell me......
Is there any way to find out how many sessions are created in server ?
Thanks in advance ..............

Only by keeping track of them yourself.
The various session listeners - SessionListener, SessionBindingListener are usefule here.

How Many Objects Are Selected

How can I tell how many objects are selected when I draw a selection marque around multiple objects?

Open the Document Info Palette.
Find its secret little flyout menu.
Select from that menu "Objects".
Let go.
Then go to that same menu all over again and select "Selection Only".
Scroll through the list and sum the quantities shown. Except be careful not to include the count of "All Text Objects" with the counts of "Point Type Objects", "Area Type Objects", and "Type On A Path Objects".
Repeat those steps every time you start a new work session in AI, because AI's palettes can't remember the way you set them between launches.
How could you have overlooked that intuitive and straightforward routine?
JET

Seing how many objects are selected.

Hi! I'm having a problem seing how many objects are selected when I navigate in Finder's windows. In Snow Leopard, there used to be a grey bar at the bottom telling you these infos, but this seems to be gone in Lion. Anyone knows how to get it back?
Thank you!

Open the Document Info Palette.
Find its secret little flyout menu.
Select from that menu "Objects".
Let go.
Then go to that same menu all over again and select "Selection Only".
Scroll through the list and sum the quantities shown. Except be careful not to include the count of "All Text Objects" with the counts of "Point Type Objects", "Area Type Objects", and "Type On A Path Objects".
Repeat those steps every time you start a new work session in AI, because AI's palettes can't remember the way you set them between launches.
How could you have overlooked that intuitive and straightforward routine?
JET

Trying to keep track of how many objects I create

Hello everyone I'm trying to keep track of how many message objects I created and Assign them to a data member.
Right now it assigns all the Message objects the same number at the end which is 3. I wanted it to assign 1 to the first object it create, 2 for the 2nd, and 3 for the 3rd.
here's a small version of my code:
package ss;
import java.util.ArrayList;
import java.util.Iterator;
public class MainTest {
     public static void main(String [] args)
          Message msg = null;
          ArrayList<Message> msgList = new ArrayList<Message>();
          for(int i = 0; i < 3; i++)
               msg = new Message();
               msgList.add(msg);
          System.out.println(msgList);
package ss;
//this class will hold the Event/Message
import java.util.List;
import java.util.HashMap;
import java.util.Map;
import java.util.ArrayList;
import java.util.Set;
import java.util.Iterator;
public class Message {
     //these are datamembers that will be used during
     //the sending of the message to the reciever
     //PacketID should be incremented each time a new message is created
     static int PacketID = 0;
     Message()
          PacketID +=1;
     public String toString() {
          return("PacketID: " + this.PacketID
                    + "\n");
}output:
[PacketID: 3
, PacketID: 3
, PacketID: 3
Any ideas what I'm doing wrong?
Thanks!

Thanks BigDaddyLovehandles,
Well there's the problem, I just posted a simpler problem to a bigger one. So I am keeping them in a collection as you can see below.
I'm keeping these message stored in a multi map, and it is multi-threaded. Everytime a user connects to my server I create a new thread, and start adding the "messages" to the database.
But I must have a packetID, meaning every new message created I need to assign that number to the message object.
I also see a problem with this like you said, its not thread safe, if 2 clients connect to the server, and both send me events, there are going to be 2 different maps, copying events from the client and storing them in their own seperate databases.
This might not be a problem because after I get the events on each thread, i send them to another server for processing.
Here's an example of what my database looks like that stores the messages:
//this class should store all the Messages or "Events" and
//you can access them based on their Serial key.
public class MessageDB {
     //database to hold the information
     //     holds the Alerts/messages
     Map<String, List<Message>> AlertMap;
     //Constructor
     MessageDB() {
          AlertMap = new HashMap<String, List<Message>>();
     //print, outputs the contents of the hashMap
     public void print() {
          //want to print out the Key and all the Messages
          //associated with that key
          //print, outputs the contents of the hashMap
               for (String key : AlertMap.keySet())
                    System.out.println("\n\nSerial (key): " + key
                              + "\nValues in Map: \n" + AlertMap.get(key));
     void add(Message msg) {
          //getting the position of the List by EntityID if avaiable
          List<Message> AlertList = AlertMap.get(msg.Serial);
          //checking to see if there is a unique Key already in the Map.
          if (AlertList == null) {
               //if there isnt a key in the map, add a new key, and a new List mapping
               //to the key EntityID;
               AlertList = new ArrayList<Message>();
               AlertMap.put(msg.Serial, AlertList);
               AlertList.add(msg);
          } else {
               //adding message to List
               AlertList.add(msg);
     }Any suggestions on what I can to number all these messages and it will be thread safe?

How many objects are in my map?

hi all
I nead help in a question about maps in java:
In one map could be stored various references with diferent keys to just one real object. How can i count all objects referenced by my map? (not all references with map.size())
Is it wise to use a set parallel to the map who contains just unique objects? Or is there an other, more beautiful solution?
many thanx for your help
benjamin

If you want a more general solution you can use an interface. Now you can store any class in MyMap as long as it implements RefCount.
interface RefCount {
   int getRef();
   void incRef();
   void decRef();
class MyValue implements RefCount {
    private int ref;
    public int getRef() {return ref;}
    public void incRef() {ref++;}
    public void decRef() {ref--;}
class MyMap extends HashMap {
    int objects = 0;
    public Object put(Object key, Object value) {
        RefCount v = (RefCount) value;
        if (v.getRef() == 0)
            objects++;        // first time inserted
        v.incRef();
        return super.put(key,value); // call superclass put
    public Object remove(Object key) {
        RefCount v = (RefCount) super.remove(key); // super class remove
        if (v != null) {
            v.decRef();
            if (v.getRef() == 0)
                objects--;        // last time removed
        return v;
    public int objectSize() { // returns number of objects.
        return objects;

How many tables are created?

          How tables does weblogic (7.0) create in database when using JMSJDBCStore? According
          to the DDL, there are only two tables; JMSSTORE and JMSSTATE.
          Jeba


That's it. Two.
          And in the next release (named 9.0?) it will likely
          go down to one.
          Tom, BEA
          Jeba Bhaskaran wrote:
          > How tables does weblogic (7.0) create in database when using JMSJDBCStore? According
          > to the DDL, there are only two tables; JMSSTORE and JMSSTATE.
          >
          > Jeba

How many WAYS are there to CREATE an OBJECT?

I simply know about implicit creation and explicit creation:
String name = "Asim Munir"; //Implicit
String name = new String("Asim Munir"); // Explicit
Do you have any other way to create an object?

Hi,
Basically in Java, an object is created by using the new keyword. This is the actual object creation. So far String is concerned, there is a trick what you have mentioned.
Plz go through it.
String str = "India"; It is also String object. But internally, Java maintains a String Constant pool to maintain the String object. When you are writing the above statement, it will first check the value "India" in the String Constant pool and it it does not find, then it will create an object. If it finds, it will not create but simply it maintain a reference to that "India" object. So here only one object is created. But in the following case.
String str = new String("India");
Here two objects are created. Just try to understand how two objects are created. If you have any problem, feel free to mail
Debadatta Mishra
[email protected]

How many java String objects are created in string literal pool by executin

How many java String objects are created in string literal pool by executing following five lines of code.
String str = "Java";
str = str.concat(" Beans ");
str = str.trim();
String str1 = "abc";
String str2 = new String("abc").intern();
Kindly explain thanks in advance
Senthil

virtuoso. wrote:
jverd wrote:
In Java all instances are kept on the heap. The "String literal pool" is no exception. It doesn't hold instances. It holds references to String objects on the heap.Um, no.
The literal pool is part of the heap, and it holds String instances.
[http://java.sun.com/docs/books/jvms/second_edition/html/Overview.doc.html#22972]
[http://java.sun.com/docs/books/jvms/second_edition/html/ConstantPool.doc.html#67960]
You're referring to the JVM. That's not Java.It's part of Java.
There is nowhere in Java where it is correct to say "The string literal pool holds references, not String objects."

How many Objects created??

Hi Friends,
I am really confused with this question,can someone please tell me how many objects would be created by the following code??My answer is two("java" on the heap and the normal new String() Object),am i right???
public class Objects{
public static void main(String[] args)    {
    String one = "Java";
    String two = "Java";
    String three = "J" + "a" + "v" + "a";
    String four = new String("Test");
}Thanks

Probably not, since all the operands are string
literals. The compiler probably sees that and instead
generates the same bytecode that it would have if it
had been coded as: "Java" in the first place. But
again, still stupid and pointless.just what i wanted to say but was a bit slow. maybe it's stupid and pointless,
but for grins, i am attaching the constants pool from the class file that was
obtained by compiling the code in post 1 with Sun's compiler. I don't see any
"J" or "a" or .........
pool index: 1 type: 10 class index: 7 name index: 16 value: null
pool index: 2 type: 8 class index: -1 name index: 17 value: null
pool index: 3 type: 7 class index: -1 name index: 18 value: null
pool index: 4 type: 8 class index: -1 name index: 19 value: null
pool index: 5 type: 10 class index: 3 name index: 20 value: null
pool index: 6 type: 7 class index: -1 name index: 21 value: null
pool index: 7 type: 7 class index: -1 name index: 22 value: null
pool index: 8 type: 1 class index: -1 name index: -1 value: <init>
pool index: 9 type: 1 class index: -1 name index: -1 value: ()V
pool index: 10 type: 1 class index: -1 name index: -1 value: Code
pool index: 11 type: 1 class index: -1 name index: -1 value: LineNumberTable
pool index: 12 type: 1 class index: -1 name index: -1 value: main
pool index: 13 type: 1 class index: -1 name index: -1 value: ([Ljava/lang/String;)V
pool index: 14 type: 1 class index: -1 name index: -1 value: SourceFile
pool index: 15 type: 1 class index: -1 name index: -1 value: Objects.java
pool index: 16 type: 12 class index: 9 name index: 8 value: null
pool index: 17 type: 1 class index: -1 name index: -1 value: Java
pool index: 18 type: 1 class index: -1 name index: -1 value: java/lang/String
pool index: 19 type: 1 class index: -1 name index: -1 value: Test
pool index: 20 type: 12 class index: 23 name index: 8 value: null
pool index: 21 type: 1 class index: -1 name index: -1 value: Objects
pool index: 22 type: 1 class index: -1 name index: -1 value: java/lang/Object
pool index: 23 type: 1 class index: -1 name index: -1 value: (Ljava/lang/String;)Vwalker

How many softwares are there to create a setup file for java programs

Hi, i am new to java
I want to know how many softwares are there to create a setup file for java programs.
I know one software i.e java launcher to create a setup file.
I want to know about any other softwares are available to create a setup file for java programs.
I created a setup file for swings program in JCreator.
And don't think that i am wastiing ur time with this question .
Help me regarding this topic.
Thanks in Advance

superstar wrote:
I want to know how many softwares are there to create a setup file for java programs.13, no wait, 42.
I know one software i.e java launcher to create a setup file.You should clearly identify what you think you already know.
I want to know about any other softwares are available to create a setup file for java programs.
I created a setup file for swings program in JCreator.Is this the one you talked before, or is this different?
And don't think that i am wasting ur time with this question .Why should I not think that?

How many objects are created?

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