Getting Java set up - javac and PATH problems..
Just as the title suggests, I am brand new to Java. I am getting the seemingly "classic" newbie Java error in comman prompt: " 'javac' is not recognized as an internal or external command, operable program or batch file." I have read help sites and threads, and I do believe it must be something wrong with my PATH environments, but I can't figure out what. Also, I have tried several different java versions, so I can only believe that my current version is jdk1.6.0_03 (According to the official website I have 6, Version 3). I am running Windows XP (Service Pack 2).
Here is the exact text as listed in the variable PATH: C:\ WINNT; C:\ WINNT\ SYSTEM32; C:\ jdk1.6.0_ 03\ bin
I also have another variable called CLASSPATH, which is: .;C:\Program Files\Java\j2re1.4.2\lib\ext\QTJava.zip
A friend suggested that I learn with DrJava, because he said that is the way he learned, but of course that only helped with learning some basic code, and it only postponed the problem I am now having to face.
I know I am utterly useless, and I am sure that whatever alien language I just put up there must be just way off base, but please bear with this poor beginner. Any help is useful, literally any, and I am going to wipe any previous thoughts of what I thought was correct away.
Are you able to set the PATH without any errors on command line ? Or another best way is to set the path in the user and system variables.
Go to
MyComputers->Properties->Advanced (tab)and click the
Environment VariablesAbove you will see
User variables
IF there is already a variable name PATH then add the
C:\jdk1.6.0_03\binElse
Click the
New type PATH as the Variable Name
and the C:\jdk1.6.0_03\bin as the variable value.
Re-start your command prompt and check with the javac or java commands.
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Java Audio Metronome | Timing and Speed Problems
Hi all,
I’m starting to work on a music/metronome application in Java and I’m running into some problems with the timing and speed.
For testing purposes I’m trying to play two sine wave tones at the same time at regular intervals, but instead they play in sync for a few beats and then slightly out of sync for a few beats and then back in sync again for a few beats.
From researching good metronome programming, I found that Thread.sleep() is horrible for timing, so I completely avoided that and went with checking System.nanoTime() to determine when the sounds should play.
I’m using AudioSystem’s SourceDataLine for my audio player and I’m using a thread for each tone that constantly polls System.nanoTime() in order to determine when the sound should play. I create a new SourceDataLine and delete the previous one each time a sound plays, because the volume fluctuates if I leave the line open and keep playing sounds on the same line. I create the player before polling nanoTime() so that the player is already created and all it has to do is play the sound when it is time.
In theory this seemed like a good method for getting each sound to play on time, but it’s not working correctly.
At the moment this is just a simple test in Java, but my goal is to create my app on mobile devices (Android, iOS, Windows Phone, etc)...however my current method isn’t even keeping perfect time on a PC, so I’m worried that certain mobile devices with limited resources will have even more timing problems. I will also be adding more sounds to it to create more complex rhythms, so it needs to be able to handle multiple sounds going simultaneously without sounds lagging.
Another problem I’m having is that the max tempo is controlled by the length of the tone since the tones don’t overlap each other. I tried adding additional threads so that every tone that played would get its own thread...but that really screwed up the timing, so I took it out. I would like to have a way to overlap the previous sound to allow for much higher tempos.
I posted this question on StackOverflow where I got one reply and my response back explains why I went this direction instead of preloading a larger buffer (which is what they recommended). In short, I did try the buffer method first, but I want to also update a “beat counter” visual display and there was no way to know when the hardware was actually playing the sounds from the buffer. I mentioned that on StackOverflow and I also asked a couple more questions regarding the buffer method, but I haven’t received any more responses.
http://stackoverflow.com/questions/24110247/java-audio-metronome-timing-and-speed-problems
Any help getting these timing and speed issues straightened out would be greatly appreciated! Thanks.
Here is my code...
SoundTest.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.io.*;
import javax.sound.sampled.*;
public class SoundTest implements ActionListener {
static SoundTest soundTest;
// ENABLE/DISABLE SOUNDS
boolean playSound1 = true;
boolean playSound2 = true;
JFrame mainFrame;
JPanel mainContent;
JPanel center;
JButton buttonPlay;
int sampleRate = 44100;
long startTime;
SourceDataLine line = null;
int tickLength;
boolean playing = false;
SoundElement sound01;
SoundElement sound02;
public static void main (String[] args) {
soundTest = new SoundTest();
SwingUtilities.invokeLater(new Runnable() { public void run() {
soundTest.gui_CreateAndShow();
public void gui_CreateAndShow() {
gui_FrameAndContentPanel();
gui_AddContent();
public void gui_FrameAndContentPanel() {
mainContent = new JPanel();
mainContent.setLayout(new BorderLayout());
mainContent.setPreferredSize(new Dimension(500,500));
mainContent.setOpaque(true);
mainFrame = new JFrame("Sound Test");
mainFrame.setContentPane(mainContent);
mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainFrame.pack();
mainFrame.setVisible(true);
public void gui_AddContent() {
JPanel center = new JPanel();
center.setOpaque(true);
buttonPlay = new JButton("PLAY / STOP");
buttonPlay.setActionCommand("play");
buttonPlay.addActionListener(this);
buttonPlay.setPreferredSize(new Dimension(200, 50));
center.add(buttonPlay);
mainContent.add(center, BorderLayout.CENTER);
public void actionPerformed(ActionEvent e) {
if (!playing) {
playing = true;
if (playSound1)
sound01 = new SoundElement(this, "Sound1", 800, 1);
if (playSound2)
sound02 = new SoundElement(this, "Sound2", 1200, 1);
startTime = System.nanoTime();
if (playSound1)
new Thread(sound01).start();
if (playSound2)
new Thread(sound02).start();
else {
playing = false;
SoundElement.java
import java.io.*;
import javax.sound.sampled.*;
public class SoundElement implements Runnable {
SoundTest soundTest;
// TEMPO CHANGE
// 750000000=80bpm | 300000000=200bpm | 200000000=300bpm
long nsDelay = 750000000;
long before;
long after;
long diff;
String name="";
int clickLength = 4100;
byte[] audioFile;
double clickFrequency;
double subdivision;
SourceDataLine line = null;
long audioFilePlay;
public SoundElement(SoundTest soundTestIn, String nameIn, double clickFrequencyIn, double subdivisionIn){
soundTest = soundTestIn;
name = nameIn;
clickFrequency = clickFrequencyIn;
subdivision = subdivisionIn;
generateAudioFile();
public void generateAudioFile(){
audioFile = new byte[clickLength * 2];
double temp;
short maxSample;
int p=0;
for (int i = 0; i < audioFile.length;){
temp = Math.sin(2 * Math.PI * p++ / (soundTest.sampleRate/clickFrequency));
maxSample = (short) (temp * Short.MAX_VALUE);
audioFile[i++] = (byte) (maxSample & 0x00ff);
audioFile[i++] = (byte) ((maxSample & 0xff00) >>> 8);
public void run() {
createPlayer();
audioFilePlay = soundTest.startTime + nsDelay;
while (soundTest.playing){
if (System.nanoTime() >= audioFilePlay){
play();
destroyPlayer();
createPlayer();
audioFilePlay += nsDelay;
try { destroyPlayer(); } catch (Exception e) { }
public void createPlayer(){
AudioFormat af = new AudioFormat(soundTest.sampleRate, 16, 1, true, false);
try {
line = AudioSystem.getSourceDataLine(af);
line.open(af);
line.start();
catch (Exception ex) { ex.printStackTrace(); }
public void play(){
line.write(audioFile, 0, audioFile.length);
public void destroyPlayer(){
line.drain();
line.close();Thanks but you have never posted reply s0lutions before ?? And F 4 is definitely not 10 times faster as stated before I upgraded !!
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I have been infected by trove adware, I was able to remove it, but I couldn't get default setting of safari and keeping bookmarks, saved passwords, ..etc
There is no need to download anything to solve this problem.
You may have installed the "Trovi," "Conduit," or "SearchProtect" ad-injection malware. Follow the instructions on this Apple Support page to remove it.
Back up all data before making any changes.
Besides the files listed in the linked support article, you may also need to remove these files in the same way:
~/Library/Application Support/Firefox/searchplugins/MyBrand.xml
~/Library/Application Support/Google/Chrome/External Extensions/fjadmdmahkpbhgbmmkiiaanlnlekelmn.json
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One of the steps in the article is to remove malicious Safari extensions. Do the equivalent in the Chrome and Firefox browsers, if you use either of those. If Safari crashes on launch, skip that step and come back to it after you've done everything else.
If you don't find any of the files or extensions listed, or if removing them doesn't stop the ad injection, then you may have one of the other kinds of adware covered by the support article. Follow the rest of the instructions in the article.
Make sure you don't repeat the mistake that led you to install the malware. Chances are you got it from an Internet cesspit such as "Softonic" or "CNET Download." Never visit either of those sites again. You might also have downloaded it from an ad in a page on some other site. The ad would probably have included a large green button labeled "Download" or "Download Now" in white letters. The button is designed to confuse people who intend to download something else on the same page. If you ever download a file that isn't obviously what you expected, delete it immediately.
"SearchProtect" may be distributed along with two other applications: "MacKeeper," which is a scam, and "ZipCloud," which, if not actually a scam, has a dubious reputation. Ask if you need instructions to remove those items.
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If it's a complex query with lots of joins and stuff, then it will be better to store it in the session as processing the query each time will take a lot of time and will decrease performance. On the other hand if the query is simple then it's advisable not to store it in the session, and fetch it each time.
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In this case storing the data is session will mean holding the stale data till the user session lasts which is not right.
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If there are large no. of data sets already present in the session, then it's strictly not advisable to store the data in the session.
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Using session cache can definitely improve performance.
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hello ....
I have to execute an application from my java program. My application called "AIMSS" takes 2 command line parameters. Now, when i mention those parameters with complete path to my executeable, windows reports that "unable to open the shortcut". Below is what i am trying:
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private static final String WIN_FLAG "url.dll,FileProtocolHandler";
private String cmd = null;
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Off the top of my head (check the api) it will be something like
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Because, my background tasks is really heavy:
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Message Edited by elset191 on 04-21-2009 10:43 AM
Tim Elsey
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hi,
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it could be helpfull if you give some code which deals the issue in detail...
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hello,
My while activity looks like this -
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I put my jsp files in a folder in WEB-INF, but CSS, and IMAGES folders are under default root folder pblic_html. Now my jsp pages don't show the images and css effects, if I correct the path manually in JSP pages, they work fine.
What is there correct way to fix it, like as done in Toystore Demo.
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ever noticed the file constant palette? Ever read the help for "current VI's path"?
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Download and save the Firefox installer to the desktop and start the installation with a double-click on the desktop icon.
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