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I have a Java program that reads some text from a file, line by line, and writes new text to an output file. But not all the text I write to my BufferedWriter appears in the output file after the program has finished. Why is that?
The details: the program takes a CSV text document and converts it into SQL commands to insert the data into a table. The text file has more than 10000 lines which look similar to following:
2007,10,9,1,1,1006134,19423882 The program seems to work fine except it just stops in the file randomly half way through creating a new SQL statement having printed it into the SQL file. It looks something like:
insert into nyccrash values (2007, 1, 2, 1, 4, 1033092, 259916); insert into nyccrash values (2007, 1, 1, 1, 1, 1020246, 197687); insert into nyccrash values (2007, 10, 9, 1 This happens after about 10000 lines but several hundred lines before the end of the file. Where the break happens is between a 1 and a ,. However, the characters doesn't seem important because if I change the 1 to a 42 the last thing written to the new file is 4, which is cutting off the 2 from that integer. So it seems like the reader or writer must just be dying after writing/reading a certain amount.
My Java code is as follows:
import java.io.*; public class InsertCrashData { public static void main (String args[]) { try { //Open the input file. FileReader istream = new FileReader("nyccrash.txt"); BufferedReader in = new BufferedReader(istream); //Open the output file. FileWriter ostream = new FileWriter("nyccrash.sql"); BufferedWriter out = new BufferedWriter(ostream); String line, sqlstr; sqlstr = "CREATE TABLE nyccrash (crash_year integer, accident_type integer, collision_type integer, weather_condition integer, light_condition integer, x_coordinate integer, y_coordinate integer);\n\n"; out.write(sqlstr); while((line = in.readLine())!= null) { String[] esa = line.split(","); sqlstr = "insert into nyccrash values ("+esa[0]+", "+esa[1]+", "+esa[2]+", "+esa[3]+", "+esa[4]+", "+esa[5]+", "+esa[6]+");\n"; out.write(sqlstr); } } catch(Exception e) { System.out.println(e); } } } 
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You're creating a new FileWriter each time through the loop, which will truncate the file each time. BufferedWriter is buffered, and you're never flushing the buffer. You need to either call bw. flush(), or even better, close the writer when done.
You need to close the filewriter else the current buffer will not flush and will not allow you to write to the file. fileWriter. flush(); //just makes sure that any buffered data is written to disk fileWriter. close(); //flushes the data and indicates that there isn't any more data.
new BufferedWriter(output); or "write", you are overwriting the "output" file. Try to make sure you only declare a new BufferedWriter once throughout the course of the program, and append() to the file instead of write().
IIRC a BufferedWriter is NOT thread-safe, so that could be an explanation, but it does NOT have to be "flushed manually" to make more room, it takes care of that itself.
You need to close your OutputStream which will flush the remainder of your data:
out.close(); The default buffer size for BufferedWriter is 8192 characters, large enough to easily hold hundreds of lines of unwritten data.
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