I am reading a csv file from a location.
Could you please tell me how can I stop the Producer Thread and Consumer Thread incase file is not found in this case ?
Below is my program which creates two threads, Producer and Consumer Threads to read the data from the file
package com.util;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.PipedReader;
import java.io.PipedWriter;
import au.com.bytecode.opencsv.CSVReader;
public class TestProgram {
public static void main(String args[]) {
final String startToken = ",Nifty 50 Gainers";
final String endToken = "50 Losers";
final PipedWriter pipedWriter = new PipedWriter();
PipedReader pipedReaderTmp = null;
try {
pipedReaderTmp = new PipedReader(pipedWriter);
} catch (IOException e) {
}
final PipedReader pipedReader = pipedReaderTmp;
// Consumer
new Thread(new Runnable() {
#Override
public void run() {
try {
CSVReader csvReader = new CSVReader(pipedReader);
while (true) {
String[] line = csvReader.readNext(); // blocks until the next line is available
if (line == null)
break; // end of stream has been reached
if (line != null && line.length > 3) {
String indices_name = line[1];
if (indices_name != null) {
System.out.println(indices_name);
}
}
}
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
}).start();
// Producer
new Thread(new Runnable() {
#Override
public void run() {
try {
BufferedReader br = new BufferedReader(new FileReader(
"C:\\Users\\ravikiranv\\Downloads\\MA050116.csv"));
String line = null;
while ((line = br.readLine()) != null) {
if (startToken.equals(line))
break;
}
while ((line = br.readLine()) != null) {
if (line.contains((endToken))) {
break;
} else {
pipedWriter.write(line + '\n');
}
}
pipedWriter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
}
See the Javadoc for PipedReader.read().
Throws:
IOException - if the pipe is broken, unconnected, closed, or an I/O error occurs.
So just close it and the other end wwil get an IOException.
Note: The PipedReader has some issues - you may find it safer/better to use something like a `BlockingQueue.
You can and should instantiate and start the Threads only if you know the file exists. This keeps you safe from the concerns to stop threads from within.
File file = new File("C:\\Users\\ravikiranv\\Downloads\\MA050116.csv");
if (file.exists()) {
new Thread(new Runnable() { ... }).start();
...
}
If you don't want that for a reason, you could keep a reference to the consumer thread and stop it from within the producer. For an example how to do that, see this answer
Related
I am learning multithread in Java. To practice, I want do multithread to read three txt files in paralel, adding each line of three files into one List. This is my code:
ArrayList<String> allLinesFromFiles= new ArrayList<String>();
Lock blockThread=new ReentrantLock();
Thread t = null;
for (String file : files) {
t= new Thread(new Runnable() {
#Override
public void run() {
try {
FileReader fichero;
fichero = new FileReader(file);
BufferedReader bufferFichero = new BufferedReader(fichero);
String line = bufferFichero.readLine();
while (line != null) {
writeList(line.toLowerCase());
line = bufferFichero.readLine();
}
bufferFichero.close();
}catch (IOException e) {
System.out.println("Error IO");
}
}
private void writeList(String line) {
blockThread.lock();
allLinesFromFiles.add(line);
blockThread.unlock();
}
});
t.start();
}
try {
t.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
Collections.sort(allLinesFromFiles);
I used lock/unlocks (ReentrantLock) in the method "writeList" to synchronize because three threads writting in the ArrayList I thought maybe is needed. Is correct? Have I to use CopyOnWriteArrayList instead of ArrayList?
I used join() to wait the finish of three threads but my code dont work correctly.
A simple way base on your code is to add an AtomicInteger count to know if the read Thread is ended or not，and the Main Thread wait for the end:
List<String> files = Arrays.asList("a.txt", "b.txt", "c.txt");
ArrayList<String> allLinesFromFiles= new ArrayList<String>();
Lock blockThread=new ReentrantLock();
AtomicInteger count = new AtomicInteger(0); // counter
Thread t = null;
for (String file : files) {
t= new Thread(new Runnable() {
#Override
public void run() {
try {
FileReader fichero;
fichero = new FileReader(getClass().getClassLoader().getResource(file).getFile());
BufferedReader bufferFichero = new BufferedReader(fichero);
String line = bufferFichero.readLine();
while (line != null) {
writeList(line.toLowerCase());
line = bufferFichero.readLine();
}
bufferFichero.close();
}catch (IOException e) {
e.printStackTrace();
System.out.println("Error IO");
}finally {
count.getAndIncrement(); // counter ++
}
}
private void writeList(String line) {
blockThread.lock();
allLinesFromFiles.add(line);
blockThread.unlock();
}
});
t.start();
}
while (count.intValue() < 3) {
TimeUnit.MILLISECONDS.sleep(500);
}
Collections.sort(allLinesFromFiles);
System.out.println(allLinesFromFiles);
But, a better way is:
List<String> filePaths = Arrays.asList("a.txt", "b.txt", "c.txt");
List<String> result = new ArrayList<>();
filePaths.parallelStream().forEach(filePath -> {
try {
List<String> strings = Files.readAllLines(
Paths.get(ReadTest.class.getClassLoader().getResource(filePath).toURI()));
result.addAll(strings);
} catch (IOException | URISyntaxException e) {
e.printStackTrace();
}
});
Collections.sort(result);
System.out.println(result);
Process p = Runtime.getRuntime().exec("myexe.exe");
BufferedReader br = null;
try{
br = new BufferedReader(new InputStreamReader(p.getInputStream(), "GB2312"));
String value = null;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
}finally{
IOUtils.close(br);
}
Then, the output likes below, not the string I want:
Child: Can't read length for data, error code 109
It seems that the problem appears, because of the output of the exe which is too long. Can ProcessBuilder solve it ?
As a general rule of thumb, you should always read the output of Process before you call waitFor (or use a background Thread to read it while you waitFor)
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
public class PBDemo {
public static void main(String[] args) throws Exception {
String s;
ProcessBuilder pb = new ProcessBuilder("myexe.exe");
pb.redirectErrorStream(true);
try {
Process pro = pb.start();
InputConsumer ic = new InputConsumer(pro.getInputStream());
System.out.println("...Waiting");
int exitCode = pro.waitFor();
ic.join();
System.out.println("Process exited with " + exitCode);
} catch (Exception e) {
System.out.println("sorry" + e);
e.printStackTrace();
}
}
public static class InputConsumer extends Thread {
private InputStream is;
public InputConsumer(InputStream is) {
this.is = is;
start();
}
#Override
public void run() {
try {
int in = -1;
while ((in = is.read()) != -1) {
System.out.print((char) in);
}
} catch (IOException exp) {
exp.printStackTrace();
}
}
}
}
In the past, I've either provided an Observer Pattern to the InputConsumer, through which some other party can be notified as new input comes in or otherwised cached the output so I can process it after the process has completed, based on your needs
I have a problem. Need to redirect process.getErrorStream(), process.getInputStream() and process.getOutputStream() to JTextPane.
Process is situated in class A, and JTextPane is situated in class B, so there isn't direct connection between them. For this purpose I've create interface. So, I can call method informListener(String message) which appends line to JTextPane. But I can't find any solution which can solve my problem. Are there any nice and easy solutions?
Thanks.
What you need is couple of threads that read the data from the input streams returned by get*Stream methods and append into the text area.
Something like:
final BufferedReader reader = new BufferedReader(new InputStreamReader(process.getErrorStream());
new Thread(new Runnable() {
String line ;
while ((line = reader.readLine()) != null) {
interfaceObject.informListener(line);
}
}).start();
Just ensure that the appending to textPane happens in EDT using SwingUtilities.invokeLater.
The following program works. (I am on OS X):
package snippet;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.logging.Level;
import java.util.logging.Logger;
public class ProcessOutput {
public static void main(String[] args) throws IOException, InterruptedException {
final Process p = Runtime.getRuntime().exec("ls -lR");
final BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
new Thread(new Runnable() {
#Override public void run() {
try {
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
} catch (IOException ex) {
}
}
}).start();
int waitFor = p.waitFor();
System.out.println(waitFor + " is the return");
}
}
Check whether your command is being constructed properly. May be just print it out and see whether you are able to execute it from cmdline.
It doesn't work. InformaListener calls another method. Here is it's code:
HTMLEditorKit kit = new HTMLEditorKit();
HTMLDocument doc = new HTMLDocument();
...
logTextPane.setEditorKit(kit);
logTextPane.setDocument(doc);
public void onLogData(final String message) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
try {
kit.insertHTML(doc, doc.getLength(), message, 0, 0, null);
} catch (BadLocationException ex) {
Logger.getLogger(SummaryPanel.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(SummaryPanel.class.getName()).log(Level.SEVERE, null, ex);
}
}
});
}
And here is code to getErrorStream:
final String exec = "cmd /C start " + batStrPath + "\\upgrade-build.bat";
final Process p = Runtime.getRuntime().exec(exec);
final BufferedReader reader = new BufferedReader(new InputStreamReader(p.getErrorStream()));
new Thread(new Runnable() {
#Override
public void run() {
try {
String line ;
while ((line = reader.readLine()) != null) {
informListener(line);
}
} catch (IOException ex) {
Logger.getLogger(Installer.class.getName()).log(Level.SEVERE, null, ex);
}
}
}).start();
p.waitFor();
I am trying to call a simple program test.exe which is as simple as-
int main()
{
int a;
cout<<"Welcome\n";
while(cin>>a&&a!=0)
cout<<"you entered "<<a<<endl;
}
I want to run it from a java program as a process, and send+recieve i/o from it. I am using the process with 2 threads as follows-
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Processproblem {
public static void main(String[] args)throws IOException, InterruptedException {
final Process process;
try {
process = Runtime.getRuntime().exec("test.exe");
} catch (IOException e1) {
e1.printStackTrace();
return;
}
new Thread(new Runnable() {
public void run() {
String line;
BufferedReader br = new BufferedReader(new InputStreamReader(process.getInputStream()));
try {
while ((line = br.readLine()) != null) {
System.out.println("[OUT] " + line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
new Thread(new Runnable() {
public void run() {
try {
byte[] buffer = new byte[1024];
int reading=0;
System.out.println(reading);
BufferedWriter bw= new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
while(reading!=-1)
{
reading= System.in.read(buffer);
for(int i = 0; i < buffer.length; i++) {
int intValue = new Byte(buffer[i]).intValue();
if (intValue == 0) {
reading = i;
break;
}
else
{
bw.append((char)intValue);
}
}
bw.newLine();
bw.flush();
}
} catch (Exception e) {
}
}
}
).start();
}
}
But they are not working as expected. When i run the program it just shows the "Welcome\n" message and then stops for input. When i give a integer and press enter in the java console it does nothing.
What am I doing wrong? They are two separate threads so why are they blocking each other? Is there any problem in my concept?
The program waits for your input. Grab the process output stream (using getOutputStream) and write to it.
I need to launch a binary file using Java and then interact with it using input and output streams. I've written a prototype to figure out how it works, but so far the only output I'm getting has been null. When run on its own however the child program produces output. What am I doing wrong?
import java.io.*;
public class Stream {
public static void main(String args[]) {
Process SaddleSumExec = null;
BufferedReader outStream = null;
BufferedReader inStream = null;
try {
SaddleSumExec = Runtime.getRuntime().exec("/home/alex/vendor/program weights.txt list.txt");
}
catch(IOException e) {
System.err.println("Error on inStream.readLine()");
e.printStackTrace();
}
try {
inStream = new BufferedReader(new InputStreamReader
(SaddleSumExec.getInputStream()));
System.out.println(inStream.readLine());
}
catch(IOException e){
System.out.println("Error.");
}
}
}
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
public class Prompt {
//flag to end readers and writer
boolean processEnd = false;
public static void main(String[] args) {
new Prompt();
}
public Prompt() {
Process SaddleSumExec = null;
Input in = new Input(this);
Output out = new Output(this);
Input err = new Input(this);
//thread to read a write console
Thread t1 = new Thread(in);
Thread t2 = new Thread(out);
Thread t3 = new Thread(err);
try {
SaddleSumExec = Runtime
.getRuntime()
.exec(
"ConsoleApplication1/bin/Debug/ConsoleApplication1");
in.input = SaddleSumExec.getInputStream();
err.input = SaddleSumExec.getErrorStream();
out.out = SaddleSumExec.getOutputStream();
t2.start();
t1.start();
t3.start();
SaddleSumExec.waitFor();
processEnd = true;
} catch (IOException e) {
System.err.println("Error on inStream.readLine()");
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public boolean isProcessEnd() {
return processEnd;
}
public void setProcessEnd(boolean processEnd) {
this.processEnd = processEnd;
}
/*Readers of Inputs*/
class Input implements Runnable {
private BufferedReader inStream;
InputStream input;
Prompt parent;
public Input(Prompt prompt) {
// TODO Auto-generated constructor stub
parent = prompt;
}
public void run() {
inStream = new BufferedReader(new InputStreamReader(input));
while (!parent.isProcessEnd()) {
try {
String userInput;
while ((userInput = inStream.readLine()) != null) {
System.out.println(userInput);
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
/*Writers of Output*/
class Output implements Runnable {
OutputStream out;
Prompt parent;
public Output(Prompt prompt) {
parent = prompt;
// TODO Auto-generated constructor stub
}
#Override
public void run() {
while (!parent.isProcessEnd()) {
try {
String CurLine = "";
InputStreamReader converter = new InputStreamReader(
System.in);
BufferedReader in = new BufferedReader(converter);
while (!(CurLine.equals("quit"))) {
CurLine = in.readLine();
if (!(CurLine.equals("quit"))) {
out.write((CurLine + "\n").getBytes());
out.flush();
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}
You don't seem to be waiting for the child process to end so it is possible that the parent process ends before it gets a chance to read the output stream.
Here is an old but excellent article around Runtime.exec
http://www.javaworld.com/jw-12-2000/jw-1229-traps.html
The correct implementation is on this page
http://www.javaworld.com/jw-12-2000/jw-1229-traps.html?page=4
From what I can tell - there could be two problems here :
Are you trying to obtain the access to the stream BEFORE the child program has started reading ?
Are you running the parent process with insufficient access rights?
If you read a null from readLine() it means the peer has closed the stream. There was no output.