problem in FileWriter

[shana07]

Hi, I am trying to write my output into a text file using FileWriter.
I have about a thousand entries in my ArrayLists.
So what happen is it just prints out the last entry. I've gone through couple examples from web about FileWriter, it involves with looping for. Could anyone please teach me how to get it printed all entries in line.
Please help me to take a look at it....really appreciate any advice. Thank you.

myArrayList.add(new Entry(data, number, value));  //If print out myArrayList.size() = 1000.
try
        {
            // WRITE ENTRY TO FILE 
            output = new BufferedWriter( new FileWriter(FILENAME));     
            output.write(data+"\n");
            output.write(number+"\n");
            output.write(value+"\n");                
            
            output.close();     
            
         } 
          
           catch (IOException e) 
           {
              System.out.println("There was a problem creating/writing to the temp file");
              e.printStackTrace();
           }

[r035198x]

Hi, I am trying to write my output into a text file using FileWriter.
I have about a thousand entries in my ArrayLists.
So what happen is it just prints out the last entry. I've gone through couple examples from web about FileWriter, it involves with looping for. Could anyone please teach me how to get it printed all entries in line.
Please help me to take a look at it....really appreciate any advice. Thank you.

 
myArrayList.add(new Entry(data, number, value)); //If print out myArrayList.size() = 1000.
try
{
// WRITE ENTRY TO FILE 
output = new BufferedWriter( new FileWriter(FILENAME)); 
output.write(data+"\n");
output.write(number+"\n");
output.write(value+"\n"); 
 
output.close(); 
 
} 
 
catch (IOException e) 
{
System.out.println("There was a problem creating/writing to the temp file");
e.printStackTrace();
}

If you search for one of the Tips posted here (the first one), you will find a way of writing to a file in append mode rather than overwriting the previous contents

[JosAH]

Hi, I am trying to write my output into a text file using FileWriter.
I have about a thousand entries in my ArrayLists.
So what happen is it just prints out the last entry. I've gone through couple examples from web about FileWriter, it involves with looping for. Could anyone please teach me how to get it printed all entries in line.
Please help me to take a look at it....really appreciate any advice. Thank you.

myArrayList.add(new Entry(data, number, value));  //If print out myArrayList.size() = 1000.
try
        {
            // WRITE ENTRY TO FILE 
            output = new BufferedWriter( new FileWriter(FILENAME));     
            output.write(data+"\n");
            output.write(number+"\n");
            output.write(value+"\n");                
            
            output.close();     
            
         } 
          
           catch (IOException e) 
           {
              System.out.println("There was a problem creating/writing to the temp file");
              e.printStackTrace();
           }

As it is now your code opens the same file everytime you add a 'record' to your
ArrayList. By opening the file for writing, any previous content of the file is erased.
So effectively the only entry in your file will be the last entry.

Either open your file in 'append' mode (see the API docs how to do it) or even
better: open the file once and keep on writing to it while you loop over your
ArrayList. At the end close the file again. The reason the second alternative is
better is that opening a file takes a relatively large amount of time. Opening and
closing it for each entry would slow down the entire process.

kind regards,

Jos

[shana07]

If you search for one of the Tips posted here (the first one), you will find a way of writing to a file in append mode rather than overwriting the previous contents

thanks, how to go the previous tips anyway...

[shana07]

As it is now your code opens the same file everytime you add a 'record' to your
ArrayList. By opening the file for writing, any previous content of the file is erased.
So effectively the only entry in your file will be the last entry.

Either open your file in 'append' mode (see the API docs how to do it) or even
better: open the file once and keep on writing to it while you loop over your
ArrayList. At the end close the file again. The reason the second alternative is
better is that opening a file takes a relatively large amount of time. Opening and
closing it for each entry would slow down the entire process.

kind regards,

Jos

Thanks for the clear explanation..re ally appreciate it. I think I prefer the second way because later I need to read them again in second execution and compare with current time entry. so I do need a loop here - using myArrayList.siz e()?

myArrayList.add(new Entry(data, number, value));  //If print out myArrayList.size() = 1000.
try
{
            // WRITE ENTRY TO FILE 
for(int i=0; i<myArrayList.size(); i++)
{                 
            output = new BufferedWriter( new FileWriter(FILENAME));     
            output.write(data+"\n");  //how to put index for these attributes then...?
            output.write(number+"\n");
            output.write(value+"\n");                
            
            output.flush()
            output.close();                 
         } 
  }
          
           catch (IOException e) 
           {
              System.out.println("There was a problem creating/writing to the temp file");
              e.printStackTrace();
           }

[r035198x]

thanks, how to go the previous tips anyway...

Links have just been provided. You should just open the file once, like Jos said there, though.

[shana07]

by putting true in the line, it appends to the same file. but I noticed the second Entry line and above it's repeated....

output = new BufferedWriter( new FileWriter(FILENAME, true));

[r035198x]

by putting true in the line, it appends to the same file. but I noticed the second Entry line and above it's repeated....

output = new BufferedWriter( new FileWriter(FILENAME, true));

Didn't really get that. What exactly is repeated? Also did you follow Jos' advice and write to the file only once?

[shana07]

Didn't really get that. What exactly is repeated? Also did you follow Jos' advice and write to the file only once?

yes. that's what I did. There are repeated output lines:
example output:
data10true
data21false
data21false // repeated twice
data32false
....//repeated 3x
and on...

my codes:

myArrayList.add(new Entry(data, number, value));  //If print out myArrayList.size() = 1000.
try
{
            // WRITE ENTRY TO FILE 
     for(int i=0; i<myArrayList.size(); i++)
{                 
            output = new BufferedWriter( new FileWriter(FILENAME, true));     
            output.write(data+"\n");  
            output.write(number+"\n");
            output.write(value+"\n");  
      } 
            output.flush()
            output.close();                 
  }
          
           catch (IOException e) 
           {
              System.out.println("There was a problem creating/writing to the temp file");
              e.printStackTrace();
           }

[r035198x]

yes. that's what I did. There are repeated output lines:
example output:
data10true
data21false
data21false // repeated twice
data32false
....//repeated 3x
and on...

my codes:

myArrayList.add(new Entry(data, number, value)); //If print out myArrayList.size() = 1000.
try
{
// WRITE ENTRY TO FILE 
for(int i=0; i<myArrayList.size(); i++)
{ 
output = new BufferedWriter( new FileWriter(FILENAME, true)); 
output.write(data+"\n"); 
output.write(number+"\n");
output.write(value+"\n"); 
} 
output.flush()
output.close(); 
}
 
catch (IOException e) 
{
System.out.println("There was a problem creating/writing to the temp file");
e.printStackTrace();
}

If that's the code you are using then you have not yet followed the advice. You are still opening the file inside the for loop meaning that it will be opened many times.

[shana07]

If that's the code you are using then you have not yet followed the advice. You are still opening the file inside the for loop meaning that it will be opened many times.

So sorry i did paste wrong one. I open file before looping and that's what I get that repeated output.

myArrayList.add(new Entry(data, number, value)); //If print out myArrayList.size() = 1000.
try
{
output = new BufferedWriter( new FileWriter(FILENAME, true)); 

// WRITE ENTRY TO FILE 
for(int i=0; i<myArrayList.size(); i++)
{ 
output.write(data+"\n"); 
output.write(number+"\n");
output.write(value+"\n"); 
} 
output.flush()
output.close(); 
}
 
catch (IOException e) 
{
System.out.println("There was a problem creating/writing to the temp file");
e.printStackTrace();
}

[ashokingroups]

Hi,
I'm new member to this site. Please don't feel bad, and my kind request is that please give 2 minutes of your valuable time.

I've registered with this site nearly 3 or 4 months before only. I sent some questions also.

While registration, I've given my mail id <email removed by ADMIN>

But, I couldn't able to get even single reply also. Now my doubt is that whether my question is appearing in the forum or not?

Could you please suggest me how to proceed so that I can post my question properly and I could able to get answers also to my mail address for them?
please.....
Thankyou.
Waiting for your reply..... Ashok kumar.

[shana07]

Hi,
I'm new member to this site. Please don't feel bad, and my kind request is that please give 2 minutes of your valuable time.

I've registered with this site nearly 3 or 4 months before only. I sent some questions also.

While registration, I've given my mail id as: ashokingroups@y ahoo.co.in

But, I couldn't able to get even single reply also. Now my doubt is that whether my question is appearing in the forum or not?

Could you please suggest me how to proceed so that I can post my question properly and I could able to get answers also to my mail address for them?
please.....
Thankyou.
Waiting for your reply..... Ashok kumar.

I think publish email add in TSDN is not permitted. So if you have any questions
you have to open discussion topic and someone will answer it there.

[r035198x]

So sorry i did paste wrong one. I open file before looping and that's what I get that repeated output.

myArrayList.add(new Entry(data, number, value)); //If print out myArrayList.size() = 1000.
try
{
output = new BufferedWriter( new FileWriter(FILENAME, true)); 
 
// WRITE ENTRY TO FILE 
for(int i=0; i<myArrayList.size(); i++)
{ 
output.write(data+"\n"); 
output.write(number+"\n");
output.write(value+"\n"); 
} 
output.flush()
output.close(); 
}
 
catch (IOException e) 
{
System.out.println("There was a problem creating/writing to the temp file");
e.printStackTrace();
}

But you are not writing data from the arraylist you should have something like

 for(int i=0; i<myArrayList.size(); i++) 
{ 
Entry entry = (Entry)myArrayList.get(i);

then

 output.write(entry.getData());

[JosAH]

So sorry i did paste wrong one. I open file before looping and that's what I get that repeated output.

myArrayList.add(new Entry(data, number, value)); //If print out myArrayList.size() = 1000.
try
{
output = new BufferedWriter( new FileWriter(FILENAME, true)); 

// WRITE ENTRY TO FILE 
for(int i=0; i<myArrayList.size(); i++)
{ 
output.write(data+"\n"); 
output.write(number+"\n");
output.write(value+"\n"); 
} 
output.flush()
output.close(); 
}
 
catch (IOException e) 
{
System.out.println("There was a problem creating/writing to the temp file");
e.printStackTrace();
}

What's bothering me is that first line: myArrayList.add ( ... ). You're not trying
to write everything to a file from a routine that adds a single element to your
list do you? If you'd add a single element again data, number, value will be
written for every element in your list, hence the repetitions.

kind regards,

Jos