Return from String method

Hi
Can anyone help me:
I have a class with a String method.
The returned value for the method is calculated in a thread. Since I have to share the same literal for the String and run methods, the returned value for the String method is not the value that the run method is supposed to calculate for me. It just wouldn't wait until it's ready.
What should I do? Can I block the String method to return the string until the run method is ready?

Look up Thread.waitFor()

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Remove Carriage return from string

I have a free text area on a BSP (a form). When users type continuously in this area the text gets wraped. When the BSP is submitted it generates a sapscript form and the text area is printed on the form, but it has '##' which are placed where the text wrapped round. I would like to remove '##', so tried the following:
replace all occurrences of '##' in text_area with ' '.
This did not work as the '##' are not recognised presumably because they are some type of carriage return and not in fact has marks.

If you dont have access to the class CL_ABAP_CHAR_UTILITIES, do this instead:
DATA: crlf(2) TYPE x VALUE '0D0A',
 itab TYPE TABLE OF string,
 w_input TYPE string.
 w_input = '<contains the text with the line feed.>'.
 SPLIT w_input AT crlf INTO TABLE itab.
Regards Michael.

Return from a method

public class A
static String str="";
public static void set(String temp)
str=temp;
public static String get()
return str;
// i want to set the value of str="" after return ?
How to set the value of a variable to "" after it returns

public class A
static String str="";
public static void set(String temp)
str=temp;
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return str;
// i want to set the value of str="" after return ?
How to set the value of a variable to "" after it
returns
public static String get() {
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}this works but I find it a bit awkward... why do you need such a thing ? why can't you call set("") afterwards instead ?

Return from a method at the end of a thread

Hi all,
I've written a slideshow in a class implementing Runnable, overriding the run() method.
I want that my a method "startSlideShow()" returns when the task of the thread ends (the thread mainly display images).
I've tried the the join() method (see code below) but the displaying of the images doesn't occurs any more.
public class SlideShow extends JPanel implements Runnable {
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public void run(){
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}I've tried several other piece of code but I didn't succeed to makes my startSlideShow() method returns when the run() method end.
Could you help ?
thank you

SlideShow slideShow = new SlideShow();
slideShow.setCompletionListener(new
ew CompletionListener() {
public void executionComplete(SlideShow source) {
//Execution will continue here when slideshow is
w is complete...
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/Kajok, thank you a lot for this. This fit my needs as the parent class of slideshow shouldn't be of a specific structure now. I will use this technic.
However, just a general remark about the threads and my wish to have a modal function.
You said that :
"As I told you, you should never ever block the AWT thread so you can't make it modal. UI programming is event driven.
and I agree. the point is that I wanted to do something like the JOptionPane set at modal.
Let's consider the jOptionPane as a metaphor (I don't want to implement my slideshow using optionPane, obviously...)
When we call a jOptionPane, we wait for an user action, then the jOptionPane returns (usually returning the results of the user action) :
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Thank for your useful answers,

How to export a reference to a table line from a method?

Hello,
I have a class which has a hashed table as an attribute. I want to retrieve a line from the table using the key and return a reference to the table line. I want changes to the return value of the method to be directly reflected in the table, as if using a local field symbol. I have tried to approaches, neither of which works.
First, I returned a reference to the local field symbol. This dumps, because after returning from the method call, the target of this reference no longer resides on the stack.
Second, I have tried using an export parameter marked as "pass by reference", i. e. without VALUE(). Strangely, this still seems to give me only a copy of the data.
What is the correct way to proceed?
Illustrative pseudo-code follows.
Thanks, Sebastian
*==============================================================
*Possibility 1: (using references)
DATA mt_key_map TYPE zt_entity. " member variable (hash table of zs_entity)
METHODS get
 IMPORTING
 !is_key TYPE zs_key
 EXPORTING
 !er_vt TYPE REF TO zs_entity.
METHOD get.
FIELD-SYMBOLS: <fs_vt> TYPE zs_entity.
READ TABLE mt_key_value WITH KEY key = is_key ASSIGNING <fs_vt>.
GET REFERENCE OF <fs_vt> INTO er_vt.
ENDMETHOD.
" Client Code:
FIELD-SYMBOLS: <fs_vt> TYPE zs_entity.
CALL METHOD get
 EXPORTING
 is_key = is_key
 IMPORTING
 er_vt = lr_vt.
ASSIGN lr_vt->* TO <fs_vt>. " will dump, because the local field symbol
 " to which lr_vt points is no longer on the stack
<fs_vt>-value = 'newdata'.
*==============================================================
*Possibility 2: (using a structure passed by reference)
DATA mt_key_map TYPE zt_entity. " member variable (hash table of zs_entity)
METHODS get
 IMPORTING
 !is_key TYPE zs_key
 EXPORTING
 !es_vt TYPE zs_entity.
METHOD get.
FIELD-SYMBOLS: <fs_vt> TYPE zs_entity.
READ TABLE mt_key_map WITH KEY key = is_key ASSIGNING <fs_vt>.
es_vt = <fs_vt>.
ENDMETHOD.
" Client Code:
DATA: ls_vt TYPE zs_entity.
CALL METHOD get
 EXPORTING
 is_key = is_key
 IMPORTING
 es_vt = ls_vt.
ls_vt-value = 'newdata'. " will not change the contents of the
 " table mt_key_value

In the first approch, try to change the exporting parameter type REF TO DATA.
Try like:
CLASS lcl_test DEFINITION.
PUBLIC SECTION.
 DATA: t_mara TYPE HASHED TABLE OF mara WITH UNIQUE KEY matnr.
 METHODS:
 constructor,
 get
 IMPORTING
 if_matnr TYPE matnr
 EXPORTING
 ea_mara TYPE REF TO data.
ENDCLASS. "lcl_test DEFINITION
START-OF-SELECTION.
DATA: lo_test TYPE REF TO lcl_test,
 lr_data TYPE REF TO data.
FIELD-SYMBOLS: <fa_mara> TYPE ANY,
 <f_field> TYPE ANY.
CREATE OBJECT lo_test.
lo_test->get(
 EXPORTING
 if_matnr = '000000000077000000' " << Replace Your Material
 IMPORTING
 ea_mara = lr_data ).
ASSIGN lr_data->* TO <fa_mara>.
ASSIGN COMPONENT 'ERSDA' OF STRUCTURE <fa_mara> TO <f_field>.
<f_field> = space.
WRITE: 'Done'.
CLASS lcl_test IMPLEMENTATION.
METHOD constructor.
 SELECT * INTO TABLE t_mara
 FROM mara
 UP TO 10 ROWS.
ENDMETHOD. "constructor
METHOD get.
 FIELD-SYMBOLS: <lfs_mara> LIKE LINE OF me->t_mara.
 READ TABLE me->t_mara ASSIGNING <lfs_mara> WITH KEY matnr = if_matnr.
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ENDCLASS. "lcl_test IMPLEMENTATION
Regards,
Naimesh Patel

Returning Internal Table as Returning Parameter of Method (by Value).

When you return an internal table as the returning parameter of a method, it is passed by value. I understand the concept of passing by value vs. passing by reference, but exactly what this means in this case is ambiguous.
1) It could mean that the entire table, including data, is copied from the local table in the method into the parameter provided by the calling code.
2) Alternatively, it could mean that only the pointer to the table is passed by value and the data is not literally copied from one place in memory to another. This would not be the same as passing by reference. For instance, I believe this is how object references are passed by value.
I want to know how it works, so that I know if there is an efficiency problem with returning a huge table. The returning parameter is wonderful for getter methods, and I prefer to use it over exporting parameters, but I have some concern about passing tables as returning parameters since I don't know how this works.
Can anyone either explain this, or at least make it clear to me whether or not there is an efficiency issue?
Thanks, in advance,
-Chris

Thanks to those who tried to help me with this question, but I finally had to just figure it out on my own. I just realized today that there is a way to find the answer using the debugger's Go To->Status Display->Memory Use option. This shows how variables are stored in memory.
The answer:
First of all, if you set one internal table equal to another like:
i_tab1 = i_tab2.
or like:
i_tab1[] = i_tab2[].
both will simply set i_tab1 to point to the same memory that i_tab2 is using. It does not make a copy. Now, if you attempt to change i_tab1, with an append statement for instance, a copy of i_tab2's memory is made then! The requested change to i_tab1 is then applied to the copied data. AHA!!! This means that even if you think you are copying a table, you are not really doing it until it becomes necessary due to a divergence in values.
I specifically tested a returning parameter to see how memory is handled, and it is basically just like an '=' statment. No copy of the data is performed at first. The memory that is allocated for the local variable in the method is simply pointed to by the variable used in the calling code to recieve that value.
What if you then change the value in the calling code after the method has finished executing? The answer depends on the situation. If the value that you returned from the method is still being pointed to by another variable somewhere, then a copy is made when you attempt to change the returned table in the calling code, but if there is no longer another variable pointing to this memory, you can change the table in the calling program all you want without causing a copy in memory.
For instance, if you have a getter method that returns the value of an attribute, at first no copy will be made, but when you try to change the table in your calling code, a copy will be made then. However, if you just fill a local table in your getter method and return that table, there will never be a copy made, because the local variable that originally pointed to that memory expired when the method completed. That means that after the method completes, the only variable pointing to the allocated memory is the one in the calling code that recieved the returning value.
This is fantastic!! This behaives in a way that seems to provide maximum efficiency in most cases. Also, the table copies are never a waste, since they only happen upon changing of one of the table variables that point to the common memory, and in this case you would want to make a copy to avoid corrupting the other variable.
Also, even if you did return your table as an exporting parameter by reference, you would not gain any significant efficiency. There would still be no table copy if you don't change the returned table. Also, if you did change the returned table, you would still produce a table copy if there was another variable, like an attribute, still pointing to the memory that you set your exporting paramter from before.
The only situation that I can see resulting in a needless efficiency problem is if someone used a getter method to return the value of a table attribute, then changed the returned table in the calling program, and then used a setter method to set the whole table attribute equal to the changed table. This would be a waste, so maybe this should be accomplished in another way.
In conclusion, there is essentially no reason to hesitate returning a whole internal table as a returning parameter from a method call, even though it is pass by value.
Kudos to the ABAP development team for their good design!

Trouble returning String from JNI method

I'm a JNI newbie who is going through the SUN online book on JNI and have put together the 2nd program example (right after "helloworld"), but it is not working right. It is supposed to prompt you for a string, then returns the string that you type in. Right now it compiles without error, but it returns only the first word that I type, not the whole sentence. What am I doing wrong?
Here's the code:
Prompt.java
package petes.JNI;
public class Prompt
 private native String getLine(String prompt);
 static
 System.loadLibrary("petes_JNI_Prompt");
 public static void main(String[] args)
 Prompt p = new Prompt();
 String input = p.getLine("Type a line: ");
 System.out.println("User typed: " + input);
}petes_JNI_Prompt.h
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class petes_JNI_Prompt */
#ifndef _Included_petes_JNI_Prompt
#define _Included_petes_JNI_Prompt
#ifdef __cplusplus
extern "C" {
#endif
* Class: petes_JNI_Prompt
* Method: getLine
* Signature: (Ljava/lang/String;)Ljava/lang/String;
JNIEXPORT jstring JNICALL Java_petes_JNI_Prompt_getLine
(JNIEnv *, jobject, jstring);
#ifdef __cplusplus
#endif
#endifpetes_JNI_Prompt.c
#include <jni.h>
#include <stdio.h>
#include "petes_JNI_Prompt.h"
JNIEXPORT jstring JNICALL Java_petes_JNI_Prompt_getLine
(JNIEnv *env, jobject this, jstring prompt)
 char buf[128];
 const jbyte *str;
 str = (*env)->GetStringUTFChars(env, prompt, NULL);
 if (str == NULL)
 return NULL; /* OutOfMemoryError already thrown */
 printf("%s", str);
 (*env)->ReleaseStringUTFChars(env, prompt, str);
 // assume here that user will ty pe in 127 or less characters
 scanf("%s", buf);
 return (*env)->NewStringUTF(env, buf);
}Thanks in advance!
/Pete

OK, I have something that works now by substituting fgets for scanf. I have two other questions:
1) Do I need to free the memory created in buf? Will it allocate memory every time the method is run? Or will it allocate only once on creation, and so is no big deal?
2) A minor question: When I run this program in eclipse, the prompt string is displayed in the console only after the input string is entered and displayed. It works fine when I run it from the command line however. I have a feeling that this is a problem with how Eclipse deals with native methods and perhaps nothing I can fix. Any thoughts?
Thanks
Pete
Addendum, the updated code:
#include <jni.h>
#include <stdio.h>
#include "petes_JNI_Prompt.h"
JNIEXPORT jstring JNICALL Java_petes_JNI_Prompt_getLine
(JNIEnv *env, jobject this, jstring prompt)
 char buf[128];
 const jbyte *str;
 str = (*env)->GetStringUTFChars(env, prompt, NULL);
 if (str == NULL)
 return NULL; /* OutOfMemoryError already thrown */
 printf("%s", str);
 (*env)->ReleaseStringUTFChars(env, prompt, str);
 //scanf("%s", buf);
 fgets(buf, 128, stdin);
 return (*env)->NewStringUTF(env, buf);
}Message was edited by:
petes1234

Return a string from a method: a problem in C++ but is it a problem in java

I have a method which return a String from it as:
String pattern(short i)
String s="":
if (i==1)
s = "test1";
else
s = "test2";
return s;
Since s is a local vaariable to pattern(), does the code above
create problems? I know it is a problem for C++ since the local
variable memory address will be reused by others and thus the
returned value may take other values sometime later or not
readable.

Actually, this is not a problem in C++ either if you
just use the string class instead of the old-style
char* from C.True, I was assuming he/she meant (in C++):
char mylocalbuf[80];
// put stuff in mylocalbuf here
return mylocalbuf;
which would be very very bad to do indeed.

NEED HELP on returning values from a method

Hello Java World,
Does anyone know how to return more then 1 value from a method..
ex.
//the following returns one value
//Person Class
private String getname()
return this.name;
how can i get two values (ex. name and occupation of person)
Thank you in advance.

Create a Class which will hold the values you want and return that object. Or return a List, or return an array, or - taking your example with the person, why don't you return the whole person object?
Thomas

Returning multiple values from a method

I have to return a string and int array from a method (both are only of size 5 for a total of 10) What would be considered the best manner in which to do this ?
Dr there's 10 points in it for you or whoever gives me the best idea ;-P

hey here it is easy that you can return many things
what ever you want from a single method man....
you know the main thing what you have to do is.....
Just create a VECTOR or LIST object, then add all the
values what ever you want to return like string and
int array like etc...
Then make the method return type is VECTOR and after
getting the Vector you can Iterate that and you can
get all the values from that method what ever you
want....
jus try this,,,,,,,,,,
Its really work......
reply me..but it relies purely on trust that the returned collection would contain exactly the right number and type of arguments

How to return more than one varibles from a method?

can you use the codes:
return var1, var2,var3;
If not, what is the correct way to do so? thanks.

You can only return 1 object from a method in Java.
However, this 1 object can contain multiple other objects. For example, a Vector object:
public Vector someMethod() {
    Vector v = new Vector();
    v.add("abc");
    v.add("xyz");
    v.add("123");
    return v;
}If these multiple objects are the same type, you can also use array to achieve want you want.
public String[] someMethod() {
    String ss = new String[3];
    ss[0] = "abc";
    ss[1] = "xyz";
    ss[2] = "123";
    return ss;
}--lichu

The problem of return value from a method

Hi everyone:
I want return a value from following method. The basic idea is that I want use Num as a parameter to get a value from a field, therefore I can input this value into another database for the display purpose by using other classes. However I got error message when I compiled it.
"method does not return a value"
I know it is a problem, but how I can fix it? I need your help. Thanks in advance.
Dawei
Method:
public int Read(int Num) {
try{
String qr1 = "select Record form Buffer where Record="+Num+"";
ResultSet rs = statement.executeQuery(qr1);
while (!rs.next()){
          int result=rs.getInt(1);
return(result);
     catch (SQLException e){
               System.err.println("Error in inserting into database " + e);
                    System.exit(1);
return 1;

"select Record form Buffer ...Hopefully "form" is actually "from" in your code.
You have three points of exit from your routine, and only two return value statements.
1 -Return inside the while loop has a value.
2- Return inside the exception block (not sure that '1' would be a valid number)
3- The very end of the method, just before the last '}' does not have a return statement.
By the way, this question has nothing to do with JDBC, so another forum might be a better place to post it.

How do you return more than one value from a method?

say I have this:
public static int myFunc(String inString)
// I want to return two values from this method
}yeah so how would i do that?

If the two values are somehow related--like a person's name and his age--define a class that has those two values as member variables--for example, Person. But only if that class and the assocation of those two quantities makes sense as an entity in your program. Don't do it just to jam to quantities into one return.
Or, if the two values are two of the same thing--person A's age and person B's age--then you can return an array or Collection.
If it doesn't fit either of those two scenarios, then your method is trying to do too much unrelated stuff and you should break it into multiple methods. For example, calculating a Person's age based on his birthdate and today's date and calculating his Body Mass Index based on his height and weight. Those two quantities should NOT be returned together.

Return from String method

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