I am new (and German so my English is not the best :D)
I am working at a program, but I need to insert a BufferedReader & FileReader.
I am working with GUI(graphical user interface) , and I know the mistake that I have to insert a throws IOException but I honestly do not know at which position. (because it is everywhere right next to public static void main(String[] args) but this does not exist in GUI)
FileReader fr = new FileReader("pi.txt");
BufferedReader br = new BufferedReader(fr);
String zeile1 = br.readLine();
char[] c = zeile1.toCharArray();
System.out.println(c[2]);
Can somebody help me?
I have never used GUI, but you can catch it with try-catch:
try{
// your code
} catch (Exception e){
}
As suggested in comment, the best way is to catch specific exception and not the generic one.
In your case, You need:
FileReader fr;
try {
fr = new FileReader("pi.txt");
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
//and
try {
String zeile1 = br.readLine();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
or
try {
// your code
} catch (FileNotFoundException e1) {
// log
} catch (IOException e) {
// log
}
Related
I have created a java gui which takes values from the user send it to python file for processing and then displays the output from the python file onto the java gui. This is working perfectly on eclipse but when i exported it into a jar file the output is not displayed. I've seen a bunch of other questions like this but they do not give a solution that would help me.
This is how i connect my python script to java.
public void connection(String name)
{
ProcessBuilder pb= new ProcessBuilder("python","recomold.py","--movie_name",name);
///System.out.println("running file");
Process process = null;
try {
process = pb.start();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
int err = 0;
try {
err = process.waitFor();
} catch (InterruptedException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
// System.out.println("any errors?"+(err==0 ? "no" : "yes"));
/* try {
System.out.println("python output "+ output(process.getInputStream()));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}*/
try {
matches.setText(output(process.getInputStream()));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private String output(InputStream inputStream) throws IOException {
StringBuilder sb = new StringBuilder();
BufferedReader br = null;
try{
br= new BufferedReader(new InputStreamReader(inputStream));
String line = null;
while((line=br.readLine())!=null)
{
sb.append(line+"\n");
//descp.setText("<html><br/><html>");
//sb.append("\n");
}
}
finally
{
br.close();
}
return sb.toString();
}
I asked a question earlier about extracting RAR archives in Java and someone pointed me to JUnrar. The official site is down but it seems to be quite widely used as I found a lot of discussions about it online.
Could someone show me how to use JUnrar to extract all the files in an archive? I found a little snippet online but it doesn't seem to work. It shows each item in the archive to be a directory even if it is a file.
Archive rar = new Archive(new File("C://Weather_Icons.rar"));
FileHeader fh = rar.nextFileHeader();
while(fh != null){
if (fh.isDirectory()) {
logger.severe("directory: " + fh.getFileNameString() );
}
//File out = new File(fh.getFileNameString());
//FileOutputStream os = new FileOutputStream(out);
//rar.extractFile(fh, os);
//os.close();
fh=rar.nextFileHeader();
}
Thanks.
May be you should also check this snippet code. A copy of which can be found below.
public class MVTest {
/**
* #param args
*/
public static void main(String[] args) {
String filename = "/home/rogiel/fs/home/movies/vp.mp3.part1.rar";
File f = new File(filename);
Archive a = null;
try {
a = new Archive(new FileVolumeManager(f));
} catch (RarException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (a != null) {
a.getMainHeader().print();
FileHeader fh = a.nextFileHeader();
while (fh != null) {
try {
File out = new File("/home/rogiel/fs/test/"
+ fh.getFileNameString().trim());
System.out.println(out.getAbsolutePath());
FileOutputStream os = new FileOutputStream(out);
a.extractFile(fh, os);
os.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (RarException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
fh = a.nextFileHeader();
}
}
}
}
This question already has answers here:
java.io.FileNotFoundException when creating FileInputStream
(2 answers)
Closed 6 years ago.
For my application I want to use a Map to act as a database. To save and load a map, I am writing/reading it to/from database.ser using this 2 methods:
private synchronized void saveDB() {
try {
fileOut = new FileOutputStream(db);
out = new ObjectOutputStream(fileOut);
out.writeObject(accounts);
fileOut.close();
out.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
#SuppressWarnings("unchecked")
private void loadDB() {
try {
fileIn = new FileInputStream(db);
in = new ObjectInputStream(fileIn); // that is where error is produced if fileIn is empty
accounts = (Map<String, Client>) in.readObject();
in.close();
fileIn.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
I want to load into Map when application starts, so I invoke method in constructor like this:
protected DriveatorImpl() {
accounts = new ConcurrentHashMap<String, Client>();
db = new File("C:/Users/eduar/git/Multy-Threaded-Bank-System/Bank-Services/database.ser");
// also, any suggestions how can I make path to a file more flexible in case I want to run Server side of an app on different machine?
if (!db.exists()) {
try {
db.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
loadDB(); // loads database when server start
}
I am aware of what causing an error, but I don't know what should I change in my design to avoid ObjectInputStream constructor receiving empty stream!
Any suggestions on what I can do differently?
Edit: I want to note that in fresh application run database.ser is empty since there was no entries made into Map yet.
Thank You!
First why the EOFExcpetion occur?
There are no contents in file or file is empty and you tried to read file.
You can avoid the EOFException for an empty file by checking file content length if it is less than or equal to zero means file is empty. another way to check if file is empty
Some code change and it worked for me.
#SuppressWarnings("unchecked")
private void loadDB() {
try {
if (db.length() <= 0) {
// if statement evaluates to true even if file doesn't exists
saveDB(); // save to a file an empty map
// if file doesn't exist, it creates a new one
// call loadDB inside constructor
}
FileInputStream fileIn = new FileInputStream(db);
ObjectInputStream in = new ObjectInputStream(fileIn); // that is where error is produced if fileIn is empty
in.readObject();
in.close();
fileIn.close();
System.out.println(accounts);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Get rid of the file.exists()/file.createNewFile() crap. All it is doing for you is masking the original FileNotFoundException problem, and turning into a thoroughly predictable EOFException because of trying to construct an ObjectInputStream around an empty stream. Handle the original problem. Don't just move it, or turn it into something else.
I am creating an application that makes calls to the Hitbox API. I am trying to get the game name (listed as category_name from a list.
Thus far, I have managed to get the game name one time during the programs running stage, however when I change where to get the game name from, the program doesn't do anything. I am at a loss as to what could cause it not to send another request to the server.
public void apiConnect(){
String channel = text.getText();
HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet("http://api.hitbox.tv/media/live/" + channel);
HttpResponse response = null;
try {
response = client.execute(request);
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
// Get the response
BufferedReader rd = null;
try {
rd = new BufferedReader
(new InputStreamReader(response.getEntity().getContent()));
} catch (UnsupportedOperationException | IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
String line = "";
try {
while ((line = rd.readLine()) != null) {
hitbox.append(line);
}
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
FileUtils.writeStringToFile(new File("hitbox.json"), hitbox.getText());
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
String game = null;
FileInputStream fileHitbox = null;
try {
fileHitbox = new FileInputStream(new File("hitbox.json"));
} catch (FileNotFoundException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
}
String strHitbox = null;
try {
strHitbox = IOUtils.toString(fileHitbox, "UTF-8");
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
JSONObject obj = new JSONObject(strHitbox);
JSONArray ar = obj.getJSONArray("livestream");
for (int i = 0; i < ar.length(); i++)
{
game = ar.getJSONObject(i).getString("category_name");
nameOf.setText("Game Name: " + game);
}
File hb = new File("hitbox.json");
if(hb.exists()){
hb.delete();
}
}
The above sample is the defined function, and the Get Game Name button code is below:
btnGetGameName.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent e) {
apiConnect();
}
});
Could anyone suggest what is causing it to not work after the first request, and if possible suggest a solution?
EDIT: I have found the issue. The reading of the data from the API is appended to the hitbox variable. I have thus added a snippet that clears what "hitbox" variable has when the button is pressed, thus meaning the code works without issues.
Try to consume your response after your read it to release the resource :
rd = new BufferedReader
(new InputStreamReader(response.getEntity().getContent()));
response.getEntity().consumeContent();
//Or if you have EntityUtils
EntityUtils.consume(response.getEntity());
source
I found something wrong when I write the Properties file by using FileOutputStream.
public synchronized static void setProperties(String file,String Properties,String value)
{
try {
FileInputStream is = new FileInputStream(file);
Properties proper = new Properties();
proper.load(is);
proper.setProperty(Properties.toUpperCase(), value);
is.close();
FileOutputStream os = new FileOutputStream(file);
proper.store(os,"Update the file:"+Properties);
os.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Look at the two lines below:
FileOutputStream os = new FileOutputStream(file);
proper.store(os,"Update the file:"+Properties);
When the first line executed, the file will be empty, until the second line execute finished. Now, I assume the second line will execute within 3 seconds. During this period, the program crashed or another reason lead to the file to be unsuccessfully written. I will get an empty Properties file when I'm running my program next time. Anyone can tell me how to prevent this kind of situation to occur?
I changed my program like below, Seems it more better than before. At least I won't get a empty properties file, Thanks all guys.
public synchronized static void setProperties(String file,String Properties,String value)
{
try {
FileInputStream is = new FileInputStream(file);
Properties proper = new Properties();
proper.load(is);
proper.setProperty(Properties.toUpperCase(), value);
is.close();
proper.store(new FileOutputStream(file+".tmp"),"Update the file:"+Properties); //Prevent empty file
File old = new File(file);
File tmp = new File(file+".tmp");
if(tmp.exists() && tmp.length()>0)
{
old.renameTo(new File(file+".old"));
tmp.renameTo(new File(file));
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}