Import Statement without ID Specification

There is an import statement
IMPORT tab g_acc_tab FROM MEMORY.
While UCChecking it.. it saying that
import statement without id specification is only used for the sake of r/2 ......
Can i Comment it ? If so won't my application go into dump while running on 6.0cc???

It has to do with packages. Most java classes are in a package, the name of which must conform to its place on the filesystem relative to the classpath. By that I mean that if you have com.mystuff.One.java, it must be in a folder com/mystuff where com is located somewhere in the classpath.
What you've done is a little different. I'm assuming a couple of things:
1. you have no package declaration at the top of one.java or two.java
2. you have the current directory "." in your classpath.
Java has the concept of the "default package", which covers classes without a declared package, and in your case is the current directory.
So when you're in c:\sourcefolder and run the compiler, then "."="c:\sourcefolder", and that directory is part of the default package. No import statements are necessary for classes that are in the same package. This is why two.java can call methods in one.java without an import statement.
When you run your jsp, the "current directory" part of your classpath is not c:\sourcefolder, but some other value (probably the directory you start your jsp engine from) You will have to import all non-java-library classes because the jsp itself becomes a java class, with a package that is determined by the jsp engine.

Similar Messages

Import statement in .java files and .jsp files

Guys I have few mysteries about this import statement.
Please correct me if I am wrong.
1)Suppose if I have a folder c:\SourceFolder it has one.java and two.java files.If I compile one.java then one.class files is created in c:\ClassFolder .Now two.java uses one of the method of one.java,and without using import statement I am able to compile two.java, and two.class file is created in c:\ClassFolder.I assume that the path of one.class was taken from the CLASSPATH environment variable,hence I there was no need for import statement .........am i right ?
BUT... in My.jsp,which is in C:\JspFolder, if I want to use one.class,then I have to specifically import the class I want to use.That is i have to say
<%@page import="one"%>
and since the classpath is C:\ClassFolder ,it finds one.class in the C:\ClassFolder.(Note that My.class is created in a folder different from c:\ClassFolder )
But I am wondering why was there no need for me to import one.class in two.java.
(Note I am using JDeveloper and Apache server)
Please help.
In this case the pSo I am wondering in JSP why it doesn't take the class I am looking for from the classpath .
Help.

You have to understand Java scoping rules. In the 1st scenario with the two Java files I am guessing neither one of them begins with a package statement. This means that they belong to the default package. When you compile the compiler uses the classpath to resolve method calls looking in the default package since there was no import statement specified in two.java. JSP is a little different. Now I just read this here in these forums a couple of days ago. Since the classfiles generated from the JSP files are not in the CLASSPATH they are loaded by a different classloader. This is why you have to import all references to all classes in the default package.

Import statement in .java files and .jsp files ..correction

Guys I have few mysteries about this import statement.
Please correct me if I am wrong.
1)Suppose if I have a folder c:\SourceFolder it has one.java and two.java files.If I compile one.java then one.class files is created in c:\ClassFolder .Now two.java uses one of the method of one.java,and without using import statement in two.java I am able to compile two.java, and two.class file is created in c:\ClassFolder.I assume that the path of one.class was taken from the CLASSPATH environment variable,hence I there was no need for import statement .........am i right ?
BUT... in My.jsp,which is in C:\JspFolder, if I want to use one.class,then I have to specifically import one.class in My.jsp .That is i have to say
<%@page import="one"%>
in My.jsp.
and since the classpath is C:\ClassFolder ,it finds one.class in the C:\ClassFolder and MyJsp is compiled sucessfully.(Note that My.class is created in a folder different from c:\ClassFolder )
But I am wondering why was there no need for me to import one.class in two.java.
(Note I am using JDeveloper and Apache server)
Please help.

It has to do with packages. Most java classes are in a package, the name of which must conform to its place on the filesystem relative to the classpath. By that I mean that if you have com.mystuff.One.java, it must be in a folder com/mystuff where com is located somewhere in the classpath.
What you've done is a little different. I'm assuming a couple of things:
1. you have no package declaration at the top of one.java or two.java
2. you have the current directory "." in your classpath.
Java has the concept of the "default package", which covers classes without a declared package, and in your case is the current directory.
So when you're in c:\sourcefolder and run the compiler, then "."="c:\sourcefolder", and that directory is part of the default package. No import statements are necessary for classes that are in the same package. This is why two.java can call methods in one.java without an import statement.
When you run your jsp, the "current directory" part of your classpath is not c:\sourcefolder, but some other value (probably the directory you start your jsp engine from) You will have to import all non-java-library classes because the jsp itself becomes a java class, with a package that is determined by the jsp engine.

What is import statement for ?

Hi all,
Sorry for asking a silly question. Since it is a new to java forum I am asking this.
What is happening when an import statement is triggered at compile time and at runtime.
What is the difference/advantages/disadvantages between importing an entire package and importing required classes only.
Is there any size limit on the generated class file.
rgds
Antony Paul

looks like we are both beguinners
i just received a newsletter from sun and in it has this
MONITORING CLASS LOADING AND GARBAGE COLLECTION
Have you ever wondered what classes are loaded when you launch an application or from where the classes are loaded? Have you ever wondered when garbage collection runs or how long it takes? The java command line tool offers several different command line options that you can use to get answers to those questions.
You might already be familiar with a number of command line options available with the java command line tool, such as -cp, -Xms, and -Xmx. The -cp option is used for specifying the classpath. The -Xms and -Xmx options are used to specify the heap size. For example, instead of setting the CLASSPATH environment variable, you can use the -cp option to tell the system to look in a specific directory for necessary class files:
java -cp ExampleDir MyExample
Here, the system will look in the ExampleDir subdirectory for the MyExample.class file and anything else needed besides the system classes. The ExampleDir in the command line tells the system to look only in the ExampleDir directory (assume that it's the parent directory). If MyExample.class is located in the current working directory, the system would not find it.
Two less frequently used command line features report on class loading and garbage collection. The -verbose:class option reports when a class is loaded into the Java virtual machine and from where it came. For instance, if you use the -verbose:class option when loading the SwingSet2 demo that comes with the J2SE 1.4.2 SDK, you get a report on the many different classes that are loaded as part of the demo, such the following two:
java -verbose:class -jar
C:\j2sdk1.4.2\demo\jfc\SwingSet2\SwingSet2.jar
[Loaded FilePreviewer]
[Loaded javax.swing.plaf.TableUI from
C:\j2sdk1.4.2\jre\lib\rt.jar]
The first line indicates that the class came from the main JAR for the demo (assuming it was started with java -jar SwingSet2.jar). The second line indicates that the TableUI class was loaded from the rt.jar file that comes with the runtime located in the c:\j2sdk1.4.2\jre directory. (From there, the rt.jar file is located in the lib subdirectory.) Different implementations of the Java platform can have different formats here. The only requirement is that -verbose:class displays messages as classes get loaded and unloaded.
Let's see when classes are loaded, and how many classes are needed for the following simple program:
public class Sample {
public static void main(String args[]) {
System.out.println("Hello, World");
Compile the Sample class. Then run it with the -verbose:class option enabled:
java -verbose:class Sample
When you run the command, you'll see that this simple program requires the opening of five jar files (such as rt.jar) and the loading of almost 250 classes.
To see an example of a class unloading message, try the -verbose:class command line option with the RunItReload class shown in the August 19, 2003 Tech Tip titled Unloading and Reloading Classes.
The -verbose:gc option reports on each garbage collection event. This includes the time for garbage collection to run, and the before and after heap sizes. This is demonstrated in the following lines:
[GC 27872K->26296K(42216K), 0.0069590 secs]
[GC 28973K->26455K(42216K), 0.0036812 secs]
[GC 29134K->26474K(42216K), 0.0016388 secs]
[GC 29117K->26487K(42216K), 0.0008859 secs]
[GC 29134K->26498K(42216K), 0.0009197 secs]
[GC 29180K->26479K(42216K), 0.0008711 secs]
[GC 29149K->26484K(42216K), 0.0008716 secs]
Like the output for -verbose:class, there is no requirement for output format, and it is subject to change without notice. The "GC" at the beginning indicates what kind of collection occurred. The number before the "->" is the heap occupancy before the collection. The number after the "->" is the heap occupancy after the collection. The number in parentheses is the currently allocated size of the heap. The seconds are the duration of the collection.
This information can be useful in debugging. For example, it could help you determine if garbage collection happened at a critical point in time, and might have caused a program to crash. This sometimes happens when mixing Java and C/C++ code with JNI, especially when there is an underlying bug on the C/C++ code side.
If you're ever curious about why it takes so long for an application to start, or if garbage collection in the middle of an operation appears to cause a problem, be sure to try out these command line options.
hope it helps

Import statement and directory structure

First of all, sorry for such a long post, I believe part of it is because I am unsure of the concept of importing in Java. Secondly, Thanks to anyone who can ultimately enlighten me to the concept of import. I did ask this question before in the "erorr and error handling" forum, and the people who have helped me there did a great job. But, I believe I require a little more clarification and thus have decided to post here.
Anyhow, my question..
Could someone explain to me the concept of the import statement, or direct me to a webpage with sort of explanation for newbies? For some reason, I am having a hard time grasping the concept.
As I understand it, the import statement in Java, is very similar to the namespace keyword in C. That is to say, import doesn't actually "import" any source code, the way that the #include statement does in C.
So I suppose what my question is, say I have a java class file like below:
//filename: sentence.java
//located: c:\school\csc365
package csc365;
class sentence
//some variables here..
//some constructor here..
//some methods here..
And some sample program like the one below which implements the above..
//filename: test.java
//located: c:\school\csc365
import csc365.*;
import java.io.*;
class test.java
//creates some sentence object
//uses the object's methods
//some other things.
As I understand it, the test.java file should not compile because the csc365 package is not in the correct directory. (assuming of course, the classpath is like c:\school\csc365;c:\school )
But, ... where then should the sentence.java be located? In a subdirectory of c:\school called csc365 (i.e c:\school\csc365\) ?
And thus that would mean the test.java file could be located anywhere on the hard drive?
I suppose, I just need a little clarification on the correlation between a package's "name" (i.e package csc365; ) and its corresponding directory's name, and also how the javac compiler searches the classpath for java classes.
..So, theoretically if I were to set the classpath to look in every conceivable directory(provided the directory names were all unique) of the harddrive, then I could compile a test.java anywhere?
As a note: I have been able to get the test.java file to compile, by leaving out the import statement in the test.java file, and also leaving out the package statement for the sentence class, but I assume this is because the files are defaulted to the same package?

Hi Mary,
No, import isn't analogous to C++ namespace - Java package is closer to the namespace mark.
import is just a convenience for the programmer. You can go your whole Java career without ever writing an import statement if you wish. All that means is that you'll have to type out the fully-resolved class name every time you want to use a class that's in a package other than java.lang. Example:
// NOTE: No import statements
public class Family
   // NOTE: fully-resolved class names
   private java.util.List children = new java.util.ArrayList();
}If you use the import statement, you can save yourself from typing:
import java.util.ArrayList;
import java.util.List;
public class Family
   // NOTE: fully-resolved class names
   private List children = new ArrayList();
}import isn't the same as class loader. It does not bring in any source code at all.
import comes into play when you're compiling or running your code. Java will check to make sure that any "shorthand" class names you give it live in one of the packages you've imported. If it can't find a matching fully-resolved class name, it'll give you a message like "Symbol not found" or something like that.
I arrange Java source in a directory structure that matches the package structure in the .class files.
If I've got a Java source file like this:
package foo.bar;
public class Baz
   public static void main(String [] args)
        Baz baz = new Baz();
        System.out.println(baz);
   public String toString()
       return "I am a Baz";
}I'll store it in a directory structure like this:
root
+---classes
+---src
      +---foo
           +---bar
                +---Baz.javaWhen I compile, I go to root and compile by typing this:
javac -d classes foo/bar/*.javaI can run the code from root by typing:
java -classpath classes foo.bar.BazI hope this wasn't patronizing or beneath you. I don't mean to be insulting. - MOD

Import statement in JSP

          Hi
          I am maintaining a system done by one of our vendors.
          Application is deployed in WLS 7.0.
          When I imported the Jsp's into my IDE , I got errors where java.util classes are
          used in the JSP's and the import statement is missing.
          Most of the Jsp's are like this,
          It is working fine in the production server.
          In the IDE i am forced to put the import statement and that is what I expect.
          But how can it work in the production server without any issue.
          Can someone advise me on this
          Thanks
          DN


<%@page import="java.util.calendar" %>
Oops... forgot the "page" in there ...That's what I get for using GUI's too much!!! :)

Javac(1.4.2) gives error in import statement

Hi All,
I am facing a surprising problem. I have 2 java class files. I write the import statement for second one in the first one. There is no package & these are in the same directory. I have compiled the second one. But when I try to compile the First one. Javac throws error at import statement like below :
D:\Clubs\oct\6>javac -d . ManojTest.java
ManojTest.java:1: '.' expected
import SessionBean;
^
1 error
My Java Files are as below :
import SessionBean;
public class ManojTest
public static void main(String args[])
//ManojTest.java
public class SessionBean
public static void main(String args[])
//SessionBean.java
I have compiled SessionBean.java successfully but when I try to compile ManojTest.java I get error mentioned above.
However this probelm comes when I use j2se 1.4.2.. but works in j2se 1.3.1..
Another way could be I use package structure.
But I can't do any of these, as I have to port my big project to j2se1.4.2.. from j2se1.3.1.. (Live project is running on Tomcat).
Problems is similar in Unix & Windows both.
Is this javac compiler issue or there is some setting which I can make.
I have already included . (dot) in PATH & CLASSPATH environment varibales.
Please help me out if there is any way around this, as i am stuck up in between
thank you
Manoj :confused:

Use a package and then add that package in your classpathOr don't use a package, leave the file in the default (noname) package, and don't use the import statement. Java will find it in the default package without the import.
Explicit import statements from the default package are no longer allowed

Length error occured in IMPORT statement

Hello everyone,
i hv one requirment in PO print(ME23N). in po print asset no nt display without changing other format.
so that i first copy both smartform and driver program, in that i made certain changes such that i declare the patameter p_ebeln and i comment to data statement of p_ebeln & p_ebeln = nest-objky.
then i join asset no (anek-anln1) with the help of inner join. then in smartform i gave condition that if bsart = 'ZCAP'
wa_final-anln1 = gv_anln1.
endif.
i import gv_anln1 in smartform and exported in deriver program.
both are synthetically currect but when i gave print preview dump is occured.
length error occured in IMPORT statement
Error analysis
    An exception occurred that is explained in detail below.
    The exception, which is assigned to class 'CX_SY_IMPORT_MISMATCH_ERROR', was
     not caught in
    procedure "%GLOBAL_INIT" "(FORM)", nor was it propagated by a RAISING clause.
    Since the caller of the procedure could not have anticipated that the
    exception would occur, the current program is terminated.
    The reason for the exception is:
    During import the system discovered that the target object has
    a different length than the object to be imported.
what i do?

Hello,
can u send me coding for that?
program line is already created for that
and their first coding is like that,
if gv_bsart = 'ZCAP'.
wa_final-matnr = space.
endif.
and in text they fetch matnr no.
but as per requirement they want asset no when bsart = 'ZCAP'
how that asset no will come.
matnr comes there is bsart is other that ZCAP, but bsart = ZCAP they want asset no instead of matnr.

Import statement question

what's the difference between
import java.util.Vector;
and
import java.util.*;
is there any difference in bytecode generated? or time takes to compile?
what's the best practice?

Yes there is a best practice, it's the one you mentioned. Use the more specific import statement. If you're only using one or two classes from a package, explicitly name them in the import statements. That way somebody else reading your code (which includes yourself, six months later) can immediately get a better understanding of your code.
If this rule is followed, and you see this as the first line of a source file:
import java.util.StringTokenizer;
then you know the StringTokenizer is being used. But if you saw this:
import java.util.*;
you wouldn't know which one is being used until you're deep in the code.
Knowing right away whether a class is tokening a string, versus say using collections, makes it a lot easier to read.
You should only use the whole-package include if you're importing a really big part of the package. For example:
import java.awt.*;
is probably OK because it's relatively unlikely a person will use only a couple classes from that package.

JSP import Statement importing a Class File giving ERROR

Hey guys,
There is a problem to which I dont know the reason,
Consider the code below:
<%@ import Converter, ConverterHome %>
It gives me a Compile Time error of this type:
'.' Required in import Converter ;
but when i put these classes in a package suppose "converter"
and the above import statement like this :
<%@ import converter.Converter,converter.ConverterHome%>
It gives me no error
So whats the reason behind this? Cant I compile a JSP program by refrencing classes without in any package?
please Reply
Thanks in advance..

So whats the reason behind this?
Cant I compile a JSP program by refrencing classes without in any package?No, I do not beleive you can, is you are using Java 1.4. In 1.4, you can only reference classes in the Default Package (none) from other classes in the default package. If you are in a package, then you can not import from the default package. And this is for ALL java classes, not just JSP and Serlets. Since the JSP servlet would be part of a package (which depends on the server you are using) you will need to put your classes into packages to import them...

Problems with IMPORT STATEMENT

Please, can someone assist me? I am using Java Studio Enterprise 8.1 & Netbeans to design a java application and input form. But the wizard keeps on generating repeated class and subclasses even after I have used the import statement. Its making my program looks clumsy.
I just want to use import statement once and start using the variable in the program without repeating the declaration.
For instance, after importing javax.swing.*, I just want to be able to specify in my program (e.g JPanel Coylogo) without the wizard generating another private javax.swing.JPanel Coylogo.
How can I do it. Please help. I will appreciate
You look at the following section of the program to unstand what I mean. Thank you.
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.*;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import javax.swing.*;
import java.sql.Date;
* @author */
public class inputForm extends JFrame
private Connection con;
private Statement stmt;
private int k;
ResultSet rs=null;
// Variables declaration - do not modify
private javax.swing.JLabel ClassLabel;
private javax.swing.JPanel Connectivitypanel;
private javax.swing.JPanel Coylogo;
private javax.swing.JCheckBox DataCapable;
private javax.swing.JLabel DateLabel;
// End of variables declaration
* Creates new form inputForm
public inputForm()
//con = new dbConnect();
initComponents();
con = dbconnection();
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
// <editor-fold defaultstate="collapsed" desc=" Generated Code ">
private void initComponents()
Coylogo = new javax.swing.JPanel();
PhoneType = new javax.swing.JPanel();
PhoneIdLabel = new javax.swing.JLabel();
ClassLabel = new javax.swing.JLabel();
phoneid = new javax.swing.JTextField();
DateLabel = new javax.swing.JLabel();
Connectivitypanel.setBorder(javax.swing.BorderFactory.createTitledBorder("CONNECTIVITY"));
pbluetooth.setText("Bluetooth");
pbluetooth.setActionCommand("bluetooth");
pbluetooth.setBorder(javax.swing.BorderFactory.createEmptyBorder(0, 0, 0, 0));
pbluetooth.setHorizontalAlignment(javax.swing.SwingConstants.TRAILING);
pbluetooth.setHorizontalTextPosition(javax.swing.SwingConstants.LEFT);
pbluetooth.setMargin(new java.awt.Insets(0, 0, 0, 0));
}// </editor-fold>
private void allPhonesTypeActionPerformed(java.awt.event.ActionEvent evt)
}

disable add imports or organize imports in your IDE

Confused about CLASSPATH and how java handles import statements...

Hello,
I must admit I don't get it. I read the articles about setting CLASSPATH etc. but I still wonder:
If you use an import statement, what does the compiler do? I.e. where does it look for the specified classes? I find it confusing because I see in different locations different .jar files:
C:\jdk1.3.1_03\lib\dt.jar
C:\jdk1.3.1_03\lib\htmlconvertor.jar
C:\jdk1.3.1_03\lib\tools.jar
and also
C:\jdk1.3.1_03\jre\lib\i18n.jar
C:\jdk1.3.1_03\jre\lib\rt.jar
C:\jdk1.3.1_03\jre\lib\jaws.jar
C:\jdk1.3.1_03\jre\lib\sunrassign.jar
Can someone explain me what the purpose is of these files?
And why do I have the same contents in
C:\Program Files\JavaSoft\JRE\1.3.1_03\lib
and in
C:\jdk1.3.1_03\jre\lib
Why is that?
Thanks for answering my questions!
-mike

Thanx for the answers, but I still wonder, everyone
here says I need to set the classpath, but I don't.Probably because your classes are already in the class path. The compiler/jvm also look for classes by themselves not just in jar files, when just a directory is supplied in the class path. And a period (".") is a valid directory.
Programs importing different classes compile with no
problem. So what's up with that?
Presumably you are referring to your own code - because they are in the class path.
Second, I still don't understand why the runtime needs
the .jar files. The runtime uses classes, like String, that have to come from somewhere.
This would also mean that end-users
need to set the classpath to the .jar files in their
JRE directory to be able to run programs that import
classes from these .jars. But this is not true, right?No it is true. The end-users will have to set the class path. There are variations on this which make it seem like no class path is set. For instance applets in a browser are java but the end-user does not need to set a class path. That is because the browser knows how to download classes/jars and how to set it up so it uses them. (Actually it uses a class loader, but that is probably more information that you need.)
Because if I make some nice classes myself and import
them, how can I expect my end-user to install these
classes and make a classpath for them?That would be between you and you end-user.
First installation is not part of java. For installation you will have to find something outside of java to accomplish the goal.
Additionally how the class path gets set is OS specific. Java does not deal with that. You will also have to find some way to deal with this (most likely part of the installation.)
There are also variations on this. For example the browser example I gave above. Or using the ext directory. Or creating an executable jar. Or simply setting the class path.
In my understanding it should only be needed in the JDK, not
in the JRE. True or am I mistaken?Mistaken. The class path is needed in the JRE as well. You will need to set it.

Not allowed to import classes without package names?

Hi,
I have a few questions on Packages and importing?
1. Is the following true that it is illegal to import classes in the same package as the current class, will this cause a comilation error? If this is the case where in the Java Language specification is this actually written as I could not find it?
2. This has probably been answered by question 1 but if I have 2 classes in the same package and if I import 1 of the classes into the other class, is it illegal to import it by just using the class name and not the package name as well, ie
if the package name is ie.tcd
and the 2 class names are exp1.class and exp2.class, can I do this in class 2
package ie.tcd;
import exp1;
public class exp2 {
3. Is it illegal to import classes that are not explicitly part of any package or must a class be part of a package to be imported. I read somewhere that while this was always illegal it is only after jdk 1.4.2 that this is being enforced? If this is the case where in the Java Language specification is this actually written as I could not find it either?
Thanks very much for any help,
John

Was just also wondering, 1 other thing, I am looking
at someone elses code they have 2 classes (Class A
and Class B) in the same package (pkg). The person
imports class A into B:
package pkg;
import A;
public class B {
Is this legal code (or was it ever)?Not if A is really in pkg.A. If there is an A in the unnamed package it was legal, or at least it was understood by the compiler, and now it isn't (to both).
Can you import or is there a point in importing a class in the same
package?Only by naming the package in the import statement. If the current and the import statement are in the same package the import is redundant.
If there is a point would you import just be
using the class name (this would be illegal after jdk
1.4) or should you use the whole package name even
though it is in the package anyways?As I understand it you must always use the whole package name in imports.

How to find export statement for Import statement ?

hi experts,
I am having an IMPORT....from memory ID statement in my program.
how could i find the location of EXPORT ...to memory ID statement for the IMPORT statement.
Pls help
saravanan.

Not possible if you are just trying to find it without knowing the links between your program and the other programs. You have to know all the objects that relate to the process that your program is automating and then you can probably dig into those related programs to see if there is an EXPORT statement there. But it is not as simple as double clicking on the IMPORT statement or doing a WHERE-USED on the memory ID.

Jsp declaration and import statement

Hi All
I have some problems with JSP.
I have wrtten a declaration in jsp like this.....
<%@ page language="java"%>
<%!
Date date = new Date();
List al new ArrayList();
public List getList(){
al.add("Hi");
return al;
%>
The List is-> <%= getList()%>
Note that i did not import anything, it gives the output without any compile time/runtime error. How it is happening?
If i write any thing in scriplets.......like List, Date, it is giving compile time error asking to import this.
I am using weblogic8.1
May i get the correct answer for this ASAP?
Thanks and Regards
Kasim
[b]

weblogic includes certain import statements in the JSP page when it is compiled.
That is why u r not getting an error some times!!
Check your weblogic documentation to find more details abt that
But it is better to include the import statements , so the code will work in any server.

Import Statement without ID Specification

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