For loop speed

Hi,
This is my vi snap shot.I would like to format array element (1D-16 bit array) into string format and N in the range of Lacks,but it will take lot of time.Could yo please tell me any solution to reduce time
thanks
Manoj
Solved!
Go to Solution.

Hi manoj,
you really should go through all those free online LabVIEW courses to learn the basics of autoindexing and shift registers!
That said I recommend to use basic functions like this:
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Similar Messages

The speed of the "for loop iteration"

Hi all:
I have written a short mini program just to test out the speed of a "for loop iteration"
package generator;
* Title: 
* Description: 
* Copyright: Copyright (c) 2004
* Company: 
* @author not attributable
* @version 1.0
private static long tmp = 0;
public static int count=0;
public synchronized long getValue(){
 long value = 0;
 value = 10 * System.currentTimeMillis();
 if(value == tmp){
 value++;
 count++;
 tmp = value;
 return value;
public static void main(String[] args) {
 for (int i=0;i<1000;i++){
 getValue();
 System.out.println("count is " + count);
}And i find that on average, count will be a value between 498-500, which probably means that on average the speed of a for loop is around 0.5 ms. But I guess the speed of the "for loop " iteration is also very much CPU dependent, could somebody possibly give me some education on this issue :) ?
Also, anybody know exactly how System.currentTimeMillis works? For example, how does it get the current time from the OS, etc. let me know.
Again, Many many thanks...

Hi all:
I have written a short mini program just to test out the speed of a "for loop iteration"You will find the overhead of the getValue() call, the increments and most importantly the System.currentTimeMillis() is what you are timing.
 public static void main(String args[]) {
 int ITER = 1000000000;
 long start = System.currentTimeMillis();
 for(int i=0;i<ITER;i++);
 long end = System.currentTimeMillis();
 System.out.println("Iterations per sec="+ITER*1000L/(end - start));
 }Prints the following Iterations per sec=576368876Running on a 1.8 GHz Intel/Windows2000

How to speed up my code inside the for loops,

how to speed up my code inside the for loops using c# WinForm.

Hi John,
Please take a look at the reply from Wyck in the following thread.
How to speed up for loop?
His answer is very comprehensive. Thanks.
Best regards,
kristin
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How can I repeat a for loop, once it's terms has been fulfilled???

Well.. I've posted 2 different exceptions about this game today, but I managed to fix them all by myself, but now I'm facing another problem, which is NOT an error, but just a regular question.. HOW CAN I REPEAT A FOR LOOP ONCE IT HAS FULFILLED IT'S TERMS OF RUNNING?!
I've been trying many different things, AND, the 'continue' statement too, and I honestly think that what it takes IS a continue statement, BUT I don't know how to use it so that it does what I want it too.. -.-'
Anyway.. Enought chit-chat. I have a nice functional game running that maximum allows 3 apples in the air in the same time.. But now my question is: How can I make it create 3 more appels once the 3 first onces has either been catched or fallen out the screen..?
Here's my COMPLETE sourcecode, so if you know just a little bit of Java you should be able to figure it out, and hopefully you'll be able to tell me what to do now, to make it repeat my for loop:
Main.java:
import java.applet.*;
import java.awt.*;
@SuppressWarnings("serial")
public class Main extends Applet implements Runnable
 private Image buffering_image;
 private Graphics buffering_graphics;
 private int max_apples = 3;
 private int score = 0;
 private GameObject player;
 private GameObject[] apple = new GameObject[max_apples];
 private boolean move_left = false;
 private boolean move_right = false;
 public void init()
 load_content();
 setBackground(Color.BLACK);
 public void run()
 while(true)
 if(move_left)
 player.player_x -= player.movement_speed;
 else if(move_right)
 player.player_x += player.movement_speed;
 for(int i = 0; i < max_apples; i++)
 apple.apple_y += apple[i].falling_speed;
 repaint();
 prevent();
 collision();
 try
 Thread.sleep(20);
 catch(InterruptedException ie)
 System.out.println(ie);
 private void prevent()
 if(player.player_x <= 0)
 player.player_x = 0;
 else if(player.player_x >= 925)
 player.player_x = 925;
 private void load_content()
 MediaTracker media = new MediaTracker(this);
 player = new GameObject(getImage(getCodeBase(), "Sprites/player.gif"));
 media.addImage(player.sprite, 0);
 for(int i = 0; i < max_apples; i++)
 apple[i] = new GameObject(getImage(getCodeBase(), "Sprites/apple.jpg"));
 try
 media.waitForAll();
 catch(Exception e)
 System.out.println(e);
 public boolean collision()
 for(int i = 0; i < max_apples; i++)
 Rectangle apple_rect = new Rectangle(apple[i].apple_x, apple[i].apple_y,
apple[i].sprite.getWidth(this),
apple[i].sprite.getHeight(this));
 Rectangle player_rect = new Rectangle(player.player_x, player.player_y,
player.sprite.getWidth(this),
player.sprite.getHeight(this));
 if(apple_rect.intersects(player_rect))
 if(apple[i].alive)
 score++;
 apple[i].alive = false;
 if(!apple[i].alive)
 apple[i].alive = false;
 return true;
public void update(Graphics g)
if(buffering_image == null)
buffering_image = createImage(getSize().width, getSize().height);
buffering_graphics = buffering_image.getGraphics();
buffering_graphics.setColor(getBackground());
buffering_graphics.fillRect(0, 0, getSize().width, getSize().height);
buffering_graphics.setColor(getForeground());
paint(buffering_graphics);
g.drawImage(buffering_image, 0, 0, this);
public boolean keyDown(Event e, int i)
 i = e.key;
if(i == 1006)
move_left = true;
else if(i == 1007)
 move_right = true;
 return true;
public boolean keyUp(Event e, int i)
 i = e.key;
if(i == 1006)
move_left = false;
else if(i == 1007)
 move_right = false;
return true;
public void paint(Graphics g)
g.drawImage(player.sprite, player.player_x, player.player_y, this);
for(int i = 0; i < max_apples; i++)
 if(apple[i].alive)
 g.drawImage(apple[i].sprite, apple[i].apple_x, apple[i].apple_y, this);
g.setColor(Color.RED);
g.drawString("Score: " + score, 425, 100);
public void start()
Thread thread = new Thread(this);
thread.start();
@SuppressWarnings("deprecation")
 public void stop()
 Thread thread = new Thread(this);
thread.stop();
GameObject.java:import java.awt.*;
import java.util.*;
public class GameObject
public Image sprite;
public Random random = new Random();
public int player_x;
public int player_y;
public int movement_speed = 15;
public int falling_speed;
public int apple_x;
public int apple_y;
public boolean alive;
public GameObject(Image loaded_image)
 player_x = 425;
 player_y = 725;
 sprite = loaded_image;
 falling_speed = random.nextInt(10) + 1;
 apple_x = random.nextInt(920) + 1;
 apple_y = random.nextInt(100) + 1;
 alive = true;
And now all I need is you to answer my question! =)

package forums;
import java.util.Random;
import javax.swing.Timer;
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
public class VimsiesRetardedAppleGamePanel extends JPanel implements KeyListener
private static final long serialVersionUID = 1L;
private static final int WIDTH = 800;
private static final int HEIGHT = 600;
private static final int MAX_APPLES = 3;
private static final Random RANDOM = new Random();
private int score = 0;
private Player player;
private Apple[] apples = new Apple[MAX_APPLES];
private boolean moveLeft = false;
private boolean moveRight = false;
abstract class Sprite
 public final Image image;
 public int x;
 public int y;
 public boolean isAlive = true;
 public Sprite(String imageFilename, int x, int y) {
 try {
 this.image = ImageIO.read(new File(imageFilename));
 } catch (IOException e) {
 e.printStackTrace();
 throw new RuntimeException("Bailing out: Can't load images!");
 this.x = x;
 this.y = y;
 this.isAlive = true;
 public Rectangle getRectangle() {
 return new Rectangle(x, y, image.getWidth(null), image.getHeight(null));
class Player extends Sprite
 public static final int SPEED = 15;
 public Player() {
 super("C:/Java/home/src/images/player.jpg", WIDTH/2, 0);
 y = HEIGHT-image.getHeight(null)-30;
class Apple extends Sprite
 public int fallingSpeed;
 public Apple() {
 super("C:/Java/home/src/images/apple.jpg", 0, 0);
 reset();
 public void reset() {
 this.x = RANDOM.nextInt(WIDTH-image.getWidth(null));
 this.y = RANDOM.nextInt(300);
 this.fallingSpeed = RANDOM.nextInt(8) + 3;
 this.isAlive = true;
private final Timer timer = new Timer(200,
 new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 repaint();
public VimsiesRetardedAppleGamePanel() {
 this.player = new Player();
 for(int i=0; i<MAX_APPLES; i++) {
 apples[i] = new Apple();
 setBackground(Color.BLACK);
 setFocusable(true); // required to generate key listener events.
 addKeyListener(this);
 timer.setInitialDelay(1000);
 timer.start();
public void keyPressed(KeyEvent e) {
 if (e.getKeyCode() == e.VK_LEFT) {
 moveLeft = true;
 moveRight = false;
 } else if (e.getKeyCode() == e.VK_RIGHT) {
 moveRight = true;
 moveLeft = false;
public void keyReleased(KeyEvent e) {
 moveRight = false;
 moveLeft = false;
public void keyTyped(KeyEvent e) {
 // do nothing
public void paintComponent(Graphics g) {
 super.paintComponent(g);
 //System.err.println("DEBUG: moveLeft="+moveLeft+", moveRight="+moveRight);
 if ( moveLeft ) {
 player.x -= player.SPEED;
 if (player.x < 0) {
 player.x = 0;
 } else if ( moveRight ) {
 player.x += player.SPEED;
 if (player.x > getWidth()) {
 player.x = getWidth();
 //System.err.println("DEBUG: player.x="+player.x);
 Rectangle playerRect = player.getRectangle();
 for ( Apple apple : apples ) {
 apple.y += apple.fallingSpeed;
 Rectangle appleRect = apple.getRectangle();
 if ( appleRect.intersects(playerRect) ) {
 if ( apple.isAlive ) {
 score++;
 apple.isAlive = false;
 g.drawImage(player.image, player.x, player.y, this);
 for( Apple apple : apples ) {
 if ( apple.isAlive ) {
 g.drawImage(apple.image, apple.x, apple.y, this);
 g.setColor(Color.RED);
 g.drawString("Score: " + score, WIDTH/2-30, 10);
private static void createAndShowGUI() {
 JFrame frame = new JFrame("Vimsies Retarded Apple Game");
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 frame.getContentPane().add(new VimsiesRetardedAppleGamePanel());
 frame.pack();
 frame.setSize(WIDTH, HEIGHT);
 frame.setLocationRelativeTo(null);
 frame.setVisible(true);
public static void main(String[] args) {
 SwingUtilities.invokeLater(
 new Runnable() {
 public void run() {
 createAndShowGUI();
}Hey Vimsie, try resetting a dead apple and see what happens.

How to optimize the select query that is executed in a cursor for loop?

Hi Friends,
I have executed the code below and clocked the times for every line of the code using DBMS_PROFILER.
CREATE OR REPLACE PROCEDURE TEST
AS
   p_file_id              NUMBER                                   := 151;
   v_shipper_ind          ah_item.shipper_ind%TYPE;
   v_sales_reserve_ind    ah_item.special_sales_reserve_ind%TYPE;
   v_location_indicator   ah_item.exe_location_ind%TYPE;
   CURSOR activity_c
   IS
      SELECT *
        FROM ah_activity_internal
       WHERE status_id = 30
         AND file_id = p_file_id;
BEGIN
   DBMS_PROFILER.start_profiler ('TEST');
   FOR rec IN activity_c
   LOOP
      SELECT DISTINCT shipper_ind, special_sales_reserve_ind, exe_location_ind
                 INTO v_shipper_ind, v_sales_reserve_ind, v_location_indicator
                 FROM ah_item --464000 rows in this table
                WHERE item_id_edw IN (
                         SELECT item_id_edw
                           FROM ah_item_xref --700000 rows in this table
                          WHERE item_code_cust = rec.item_code_cust
                            AND facility_num IN (
                                   SELECT facility_code
                                     FROM ah_chain_div_facility --17 rows in this table
                                    WHERE chain_id = ah_internal_data_pkg.get_chain_id (p_file_id)
                                      AND div_id = (SELECT div_id
                                                      FROM ah_div --8 rows in this table
                                                     WHERE division = rec.division)));
   END LOOP;
   DBMS_PROFILER.stop_profiler;
EXCEPTION
   WHEN NO_DATA_FOUND
   THEN
      NULL;
   WHEN TOO_MANY_ROWS
   THEN
      NULL;
END TEST;The SELECT query inside the cursor FOR LOOP took 773 seconds.
I have tried using BULK COLLECT instead of cursor for loop but it did not help.
When I took out the select query separately and executed with a sample value then it gave the results in a flash of second.
All the tables have primary key indexes.
Any ideas what can be done to make this code perform better?
Thanks,
Raj.

As suggested I'd try merging the queries into a single SQL. You could also rewrite your IN clauses as JOINs and see if that helps, e.g.
SELECT DISTINCT ai.shipper_ind, ai.special_sales_reserve_ind, ai.exe_location_ind
           INTO v_shipper_ind, v_sales_reserve_ind, v_location_indicator
           FROM ah_item ai, ah_item_xref aix, ah_chain_div_facility acdf, ah_div ad
          WHERE ai.item_id_edw = aix.item_id_edw
            AND aix.item_code_cust = rec.item_code_cust
            AND aix.facility_num = acdf.facility_code
            AND acdf.chain_id = ah_internal_data_pkg.get_chain_id (p_file_id)
            AND acdf.div_id = ad.div_id
            AND ad.division = rec.division;ALSO: You are calling ah_internal_data_pkg.get_chain_id (p_file_id) every time. Why not do it outside the loop and just use a variable in the inner query? That will prevent context switching and improve speed.
Edited by: Dave Hemming on Dec 3, 2008 9:34 AM

Is there a way to run a For Loop independently within a While Loop in LabVIEW 2013?

In my program I would like to run a For loop inside of a While loop, and have them run independently, at their own execution rates. As a test, I wrote a simple VI with a While loop with 1 second timing, and into this I inserted a For loop with 3 second timing. I created indicators for both iteration terminals. Upon running the VI, I found the While loop waits for the For loop to run N times before the While loop executes again. I also found that sometimes the first iteration of the For loop will end at 1 second rather than 3 seconds, and the STOP button to terminate execution of the While loop does not always work.
Solved!
Go to Solution.

ksinks wrote:
Thanks, how would you synchronize the loops? I have gone through the Getting Started exercises and manual.
Why would synchronization matter? Did you want them to run independantly at their own speed or not?
Regardless, there's a synchronization pallette with functions for this, as Occurance.
Other solutions include a common loop counter and a case structure executing every X'th iteration, or having the faster loop send a queue or event every X'th loop that controls the slower loop.
/Y
LabVIEW 8.2 - 2014
"Only dead fish swim downstream" - "My life for Kudos!" - "Dumb people repeat old mistakes - smart ones create new ones."
G# - Free award winning reference based OOP for LV

Question about using for-loop to generate array from DAQmx. Thanks!

I have a laser system with a frequency of 1kHz, I am using this 1kHz signal to trigger the DAQmx and get the data from a photodetector, e.g. I will get 1000 data points during 1 second from DAQmx, but I need to separate this 1000 data points into the even and odd list, which is two list of 500 data points, e.g.. The 1st, 3rd, ... 99th data is one array, the 2nd, 4th,... 10th data is another array, then I will do further calculations based on these two arrays.
To seperate the even and odd data, the only way I can find is put these 1000 points into an array and then seperate them afterwards.
Can I do things like this pic?
I don't know the speed of the for loop, because the 1kHz trigger is always there, once it is triggered, the DAQmx read will give a data point, if the speed of the for-loop( the time from the end of a loop to the beginning of the next loop) is slower than the 1kHz trigger, then the for-loop will miss data point, then the ordering of the 1000 points in 1 second will be changed.
Or I need to put everything, e.g. AI Voltage, Trigger, sample clock, into the for-loop and then return a Y? Thanks!

Clarification:
The VI you have posted will work as following:
1) The task will read 2 analog inputs (ai0, ai3).
2) The acquisition starts, oncece digital signal (trigger) is detected on PFI0
3) The sampling rate will be as specified in "rate" control - it is continuous analog input acquisition, which means that after trigger is received (point 2), the board will start to generate hardware clock with frequency you specify as "rate"
4) with each rising edge of that hardware clock, the measurement is taken, and stored into buffer of driver.
5) DAQmx read will try to read "number of samples per channel" number of samples each time is called - and if there is not enough measurement stored in buffer (step 4), then DAQmx read will wait until DAQ card will measure reaquested number of samples (or timeout occurs before requested number of samples has been acquired)
6) DAQmx read will be then called 1000 times - so totaly you will read 1000 * "number of samples per channel" number of samples.
You do not have to be worried about speed of the loop. In fact, if you need to read just 1000 samples, with 1kS/s, then you can remove for loop and you can change measurement mode from continuous to finite samples, and specify number of samples to read to be 1000. You will read them all properly. I recomend you to read User Manual for your DAQ device - lets say M Series User Manual.
I hope it is clear now.
regards,
stefo

Can a waveform graph be used without for loop

i would like to know if a waveform graph can be used without a for loop and if so, how? I tried using a while loop only, but the reading becomes too fast.
can someone advise

Dear nebb,
first of all, graph is usually an offline plot of the acquired data but to use it as an online display u need to use build arrays in for/while loop which keeps on adding new points & plots in waveform graph.
I am including a vi which incorporates a while loop in which by using build array, points keep on increasing & simultaneously they are plotted in the waveform graph.
Using for or while loop, it has no concern with speed. it depends on the code inside the loop which makes them faster or slower.
For making slow readings, you can put some delay inside while looping.
Hope this works. YOur feedbacks are welcome.
Best Regards,
Nirmal Sharma
India
Attachments:
waveform_graph_without_for_loop.vi ‏17 KB

How can I get the highest control loop speed?

currently I am doing a nonlinear control.
whose control loop speed is higher than 20k.
My PXI is 8145 and 8175 , with DAQ card 6040E.
Each time I need only one point in and then processing , then output a point.

I would recommend configuring your program like the example program, Real-Time PID Control.vi, that ships with LabVIEW. You can find it in LabVIEW by going to Help->Find Examples and type "PID" on the search tab. The Real-Time PID Control.vi shows a good way to design your program for a single point in, single point out application.
If you're aiming for a 20KHz loop speed, you may not be able to attain this with the PXI-8175, assuming you also have a normal priority loop running to handle the communication back to the host computer. To time your code, you can use the NI Timestamp Code Time.vit template that comes with LabVIEW 7 Express. The PXI-8176, benchmarked for sinlge point PID loop rates up to 40 KHz, may be a better solution for you application.
It is
also a good idea to disable the USB port and to install only the RT drivers you need. For information on how this is done, follow this link.
Please let me know if you have further questions.
Regards,
Kristi Hummel
Applications Engineer
National Instruments

Compiling executables loop speed

I am trying to optimize speed in my application and was wondering
whether compiling vi's as executables affect loop speed (i.e. for PID
applications) at all? Also, I have read that this option
only exists for the Pro Package and was wondering if the "Mass Compile"
option in the Base Package would have any effect either?
Thanks,
Nick

Every time you run a VI, you are running a compiled program. The application builder creates an executable but does not do any extra compilation that has not already been done. The VIs in the exe are built without diagrams and without any debug code and this will result in some slight improvement but usually not anything you can notice. Optimization in the VI can be done in a number of ways. You should start with the shipping document called LabVIEW Performance and Memory Management. This is part of the LabVIEW Bookshelf you can access from the Help menu.

For Loop Parallelization

Hi All,
I need to run an algorithm on 12 images. One way would be to run it in a for loop sequentially. However this will take a long execution time.
So after searching a little I found that an alternative to speed up execution is by the using parallelized for loop- as seen here.
I have 1 subvi(lets call it-mytry1.vi) which is present inside the parallel loop. mytry1.vi is preallocated re-entrant.
mytry1.vi uses functions from image processing toolkit and contains shift registers. All the library functions are also made re-entrant(by default they are shared and not pre-allocated).
My PC config is intel dual core 2.0 GHz and I'm using LabVIEW 2013.
When I use Find Parallelizable loops (Tools->>profile->>) to see whether mytry1.vi is parallelizable or not, I get the following result
for loop 1 : Possibly not parallelizable - One or more nodes in the For Loop may have side effects.
I ignore this and make it a Parallelized for loop(this does not throw any error).
When I run the vi, it is behaving as a sequential for loop rather that parallelized.
Why does this happen? Is it because of the use of shift registers??
Regards
Aveo

Shift Registers themselves would not cause a problem. Unitialized Shift Registers, however, could cause all kinds of interesting issues with state. But that has nothing to do with your loops behaving serially.
I'm thinking it could potentially be the DLLs the toolkit calls are not thread safe. They could potentially be set to run in the UI thread, which would cause the serial processing you are seeing.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Creating an array in a 'for' loop (resetting loop count)

Hi,
I am trying to integrate an acceleration signal coming from a CRIO analogue input to obtain the speed and then further integrate to get the displacement of a vibration system.
I understand that in order to perform the integration, an array has to be fed in. My problem is that I could not buffer the signal in a buffer block as I couldn't find any buffer blocks. so I decided to create my an array of data using a 'for' loop. The 'for' loop nests inside a timed loop. The problem that I got stuck at is how to reset the 'for' loop in order to refill the buffer again at every iteration of the outer timed loop.
I have attached the code if that helps. Note that I am using labview 2013.
I would be gratefull if someone who had encountered a similar issue before can help me.
Regards
Ali
Solved!
Go to Solution.
Attachments:
acc_test.vi ‏42 KB

Dear Altenbach,
Many thanks for your reply.
I need to make it clear that I have not had enough hands-on with labview, I have only used it for sometime in the past and now I have to in order to perform some active damping on a 50Hz running machine. I must stress the fact that what i find more intuitive to do in a different programming language (matlab or C) is not as straightforward in labview. so please bear with me if my code has basic mistakes .
All what i am trying to do is obtain the speed and position from an acclerometer signal. unfortunately i dont have a position sensor so i have to measure acceleration then perform time integrations in order to obtain the speed and position respectively. I am using a compact Rio (later in FPGA mode) to take physical measurements of acceleration from the vibratory machine and where i managed to do this bit successfully. when it came to performing the integration, i had to create an array inside my timed loop since i couldn't find a buffer block. I implemented a 'for' loop inside a timed loop in order to build the array. however i got stuck at resetting the count of the 'for' loop in order to refill the array with new values at every new iteration of the outer timed loop. unfortunately, even a sensible answer has been suggested before, i dont seem to have been capable of doing it yet. I really spent all my day trying to figure a way out but not achieved it yet, nevertheless I have learnt many many things by playing around.
I would be gratefull if you could comment on a possible way of doing what i am trying to do.
Kind Regards
Ali

Parallelized for loop progress bar

I have a for that takes a long time to execute and enabled parallelism to speed things up. I also want a progress bar. Before enabling parallelism, I simple had an indicator wired to the iteration counter and the array size that is being processed. This gave a good percent complete indicator. With the for loop parallelized, the indicator bounces around depending on which instance of the for loop happens to update the indicator. Is there a way to have an indicator inside a parallelized for loop?
Solved!
Go to Solution.

altenbach wrote:
A better idea is probably a simple action engine that increments with each call, incrementing an integer in a feedback node, and returns the total count. Since it is not reentrant, it will be shared by all loop instances.
Here's a very quick draft. See if it works for you. (Warning, only use it in one FOR loop overall).
Probably needs a few tweaks....
LabVIEW Champion . Do more with less code and in less time .
Attachments:
ParallelProgress.zip ‏14 KB

Difference between open,fetch,close and a for loop

Is there much difference in looping a query using fetch loop or a for loop?
Example:
For x in (select * from ....) loop
end loop;
and
OPEN c_cursor;
LOOP
FETCH c_cursor INTO myVar;
EXIT WHEN c_cursor%NOTFOUND;
END LOOP;
close c_cursor;
Let's say we have a few thousand users using a function that uses this code. Would you see much difference in speed? Suppose i forget to close the cursor in the second example. Will that be a major issue if we have a very large userbase or with oracle close the cursor themself after a while? The cursor wont lock the record, right? So even if we forget to close the cursor we won't get a deadlock i suppose. Only if we declare the cursor for update but that's not the case.

simple test case to prove the point
SQL> create or replace function myFunc return number
2 is
3 cursor mycursor
4 is
5 select * from dual;
6
7 myvar dual.dummy%type;
8 Begin
9 open myCursor;
10
11 fetch myCursor into myVar;
12
13
14 if myCursor%found
15 then
16
17 return 1;
18 else
19 return 0;
20 end if;
21
22
23 close myCursor;
24 end;
25 /
Function created.
SQL> show parameter open_cursor
NAME TYPE VALUE
open_cursors integer 300
SQL>
SQL> select myfunc from dual connect by level <= 350
2 /
 MYFUNC
 1
 1
 1
 1
 1
 1
 1
 1
 1
 1
 1
350 rows selected.
SQL>See i dont hit any error

Getting the label of a JButton in a for loop

hi,
I doing a project for my course at the minute and im in need of a bit of help. I have set up 1-d array of buttons and i have layed them out using a for loop. I have also added an annoymous action listener to each button in the loop. It looks something lke this:
b = new JButton[43];
for (int i=1; i<43; i++)
b[i] = new JButton(" ");
b.addActionListener(
new ActionListener()
public void actionPerformed(ActionEvent e)
 System.out.println("..........");
}); // addActionListener
} // for
I want the "System.out.println( ..." line, to print out the "i" number of the button that was pressed but i cannot figure out how to do it. I cannot put "System.out.println(" "+i);" as it wont recognise i as it is not inside the for loop. Does anyone have any suggestions?
Thanks!!

class ButtonExample extends JFrame implements ActionListener{The OP wanted to have anonymous listeners, not a subclassed JFrame
listening to the buttons. I don't know if the following is the best design,
since the poster has revealed so little, but here is how to pass the
loop index to an anonymous class.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ButtonExample {
 private JButton[] buttons = new JButton[24];
 public JPanel createGUI() {
 JPanel gui = new JPanel(new GridLayout(6, 4));
 for(int i=0; i<buttons.length; i++) {
 final int ii = i; //!! !
 buttons[i] = new JButton("button #" + i);
 buttons.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent evt) {
System.out.println("number " + ii);
gui.add(buttons[i]);
return gui;
public static void main(String[] args) {
ButtonExample app = new ButtonExample();
JPanel gui = app.createGUI();
JFrame f = new JFrame("ButtonExample");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().add(gui);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);

For loop speed

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