I/O / Streams :: Does Printwriter Always Truncates Existing File To 0 Size Before Adding Any New Data
Jun 13, 2014Does printwriter always truncates the existing file to 0 size before adding any new data ??
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I/O / Streams :: Appending To Existing File Instead Of Overwriting It
Jul 24, 2014I do most of my file I/O with {Scanner} for input and {PrintWriter} for output. I've got lots of places in my code that looks like:
Scanner source = new Scanner( new File( sourceName));
PrintWriter dstntn = new PrintWriter( new BufferedWriter( new FileWriter( dstntnName)));
But when I call the constructor for {PrintWriter} up above, it overwrites whatever the original contents of the file designated by {dstntnName} were, doesn't it? Is there a way to call the constructor so that any future writes to it simply append to the original contents, instead of overwriting them?
I/O / Streams :: File Size Comparison
May 20, 2014I would like to create a component to detect the file being modify before process.is it the right way to detect the file modification based on file size value?
Below are the flow:
1. Get the file size of a file
2. Used file size value encrypt it with MD5 algorithm, and say it generated us encrypted value "0123sdf"
3. to avoid user modify the file content, before file process, we take the file and do the encryption with md5 again, if it return value "0123sdf", then we are sure it doesn't have modification.
my question:
a. is it the right approach to detect file modification?
b. what the library advise to use or using java.security.DigestInputStream will do?
Writing Data To A File Using PrintWriter
Oct 25, 2014I am creating a car simulator that simulators the odometer and fuel gauge on a car. I want to print the results to a text file but it seems to be printing only the last two lines instead of all of them. How can I make it so it doesn't overwrite the previous input?
Here's my main method:
public static void main(String[] args) throws FileNotFoundException {
CarInstrumentSimulator carInstrumentSimulator = new CarInstrumentSimulator();
FuelGauge gas = carInstrumentSimulator.new FuelGauge();
[Code].....
I/O / Streams :: How To Grab Last One Hour Data From Log File
Jul 17, 2014I have a log file which goes like this..
INFO: Jul 07 00:00:15 DataSource 2zvw8p93107gev14wko86|34e51ca2: Total connections 4 idle 4 busy 0 unclosed orphans 0 pool unknown
PERFORMANCE: Jul 07 00:00:15 Garbage Collection: ParNew 5 51ms in 59 seconds. [SpeedoLoggingBean] Thread SpeedoBean
INFO: Jul 07 00:00:15 Speedo: 2,222,786K of 4,054,528K - 1,831,741K free, 4,952epm, 1 buffered, 216 threads, 49.1% CPU, permgen 173,731K of 262,144K - 88,412K free
Jul 7, 2014 12:00:15 AM org.geotools.data.wfs.v1_0_0.WFSTransactionState commit
SEVERE: number of fids inserted do not match number of fids returned by Transaction Response. Got:1 expected: 0
[code].....
What I need is to grab only the last hour data from this log file?
I/O / Streams :: FileOutputStream Is Not Writing Data To A File?
May 25, 2014My program creates a file but cannot write to it and i cannot figure out why.
How can i fix this code so that the FileOutputStream writes the String "Output" to the file HighScore.
public boolean ScoreWriter(int HighScore, int ScoreNum){
boolean writ = true;
System.out.println(HighScore + " " + ScoreNum);
try{
File ScoreFile = new File("HighScore");
if (!ScoreFile.exists()){
ScoreFile.createNewFile();
}else if (ScoreFile.exists()){
ScoreFile.delete();
ScoreFile.createNewFile();
[code].....
I/O / Streams :: POI - Log File To XLSX / Writing Data In Unreadable Format
Jul 16, 2014When I am trying to read data from BufferedReader and writing into excel using FileOutputStream object with POI APIs then i am getting the data in excel file in bad formats. you can check the log file and excel file attached for more information.
Here my problem is I cannot use BufferedWriter in place of FileOutputStream because POI class XSSFWorkbook only have one write method and we can only pass FileOutputStream class object there.
public void readFile()throws IOException {
BufferedReader inputStream = null;
FileInputStream fis=null;
InputStreamReader isr = null;
//Blank workbook
XSSFWorkbook workbook = new XSSFWorkbook();
[Code] .....
I/O / Streams :: Reading From And Writing To A File Then Read Again Including Data Written
Oct 11, 2014I'm having a bit of trouble with using the Scanner and the Printwriter. I start with a file like this (1 = amount of Houses in the file)
1
FOR SALE:
Emmalaan 23
3051JC Rotterdam
7 rooms
buyprice 300000
energylevel C
The user gets (let's say for simplicity) 3 options:
1. Add a House to the file,
2. Get all Houses which fullfil requirements (price, FOR SALE / SOLD etc.) and
3. Close the application.
This is how I start:
Scanner sc = new Scanner (System.in);
while (!endLoop) {
System.out.println("Make a choice);
System.out.println("1) Add House");
System.out.println("2) Show Houses");
System.out.println("3) Exit");
int choice = sc.nextInt();
Then I have a switch for all of the three cases. I keep the scanner open, so Java can get the user input (house = for sale or sold, price = ... etc). If the user chose option 1, and all information needed is inputted and scanned, the House will be written to the file (which looks like what I typed above).
For this, I use try (PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("Makelaar.txt", false)))). This works perfectly (at least so it seems.)
If the user chose option 1, and all requirements are inputted and scanned, the Houses will be read (scanner) from the file and outputted. For this I use the same Scanner sc. This also works perfectly (so it seems atleast).
My problem is as follows: If a House has been added, I can only read the House(s) which were already in the file. Let's say I have added 2 houses, and there were from the start 3 houses. If option 2 is chosen, the first 3 houses will be scanned perfectly. An exception will be caught for the remaining 2 (just added) Houses. How can I solve this? I tried to close the Scanner, and reopening it, but apparently Java doesn't agree with this
I/O / Streams :: Report Generation Tool For Huge Data In Different File Formats
Apr 8, 2014I need to generate reports for huge data (around 2 to 5 lakh records) in different file formats (PDF , XLS , RTF , XML) in my web application.
Data will be fetched from database.
I have been searching for a best open source report generation tool and ended up on choosing on Dynamic Reports.
Aspose , is licensed and unluckily we could not afford to at this moment.
Whether i can use Dynamic Reports , or is there any other tool available.
I/O / Streams :: Unable To Write Sample Data Into Newly Created File
Nov 29, 2014My code below creates the 2 files successfully, but it is not able to write the sample data into the newly created file. I can't figure out the reason why.
Another strange thing is that when I tried inserting System.out.println calls for debugging, nothing prints out.
try{
// stuff here
}
catch(FileNotFoundException fileNF){
String dirString = System.getProperty("user.dir");
String defaultFile = "config";
String currentFile = "currentconfig";
Path filePath = Paths.get(dirString, defaultFile);
Path filePath2 = Paths.get(dirString, currentFile);
[Code]...
Adding Logo Into Existing Program
Mar 15, 2014So I am trying to add a logo to my existing program. However nothing shows up when I run it. I am getting no errors and everything else seems to be fine. This is just the logo part if you need the whole code it will be separate (just trying to make things easier.
class Logo extends JPanel {
public Logo() {
super();
setPreferredSize(new Dimension(200,200));
}
public void paint(Graphics g) {
g.setColor(Color.red);
g.fillRoundRect(60,60,110,90,5,5);
g.setColor(Color.black);
g.drawString("DEAD BUG", 70, 105);
[code]....
Adding User-defined Int To Existing Array?
Apr 7, 2015how to add an a user defined int into my existing array. Ive heard of using ArrayList but not sure how to implement it.
View Replies View RelatedAdding Elements To Existing JList Under Java 7
Mar 14, 2014I know there was a change in the later versions of Java where the C++ equivalent of a <template type> was added. Unfortunately the change has 'broken' my older code. If I have a JList and I want to add elements to it then now I should specify the type e.g., the list will store Strings. When I do this and then add data to the list (or actually the list model) the code is ''fixed". However if after adding those new elements to the list I later need to add more elements, which isn't unreasonable for a list...to have elements added dynamically at run time then I again get the same compiler error message that I haven't correctly specified the type:
// Error message during compilation
Note: Driver.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
// My code
// Problem here: I try to add new elements to the list. It's the very last line of the method that results in the error. I tried various things such as:
// model.addElement(<String> s);
// but so far nothing has worked. How do I add new elements to the list (model)?
public static void m2(JList <String> list)
{
String s;
int i;
String [] array = new String[10];
[Code] ....
// Code is OK: Create the array of strings to add to constructor of the JList
public static String[] m1(){ String s;
int i;
String [] array = new String[10];
for (i = 0; i < 5; i++)
array[i] = i + "*"; return(array);
[Code] ....
// The change I had to make when compiling under the newer version of Java to indicate that the list would store strings
// Things are okay here now but then when I try to add new elements to the model via method 'm2' that's where I get the compiler error
Adding Data File Into Two Separate 2D Arrays In Java
Apr 27, 2014I am having some trouble with a Java program. I have a txt data file, which I will display, that I need to add into two separate arrays. The text file is 8 lines long that is supposed to go into two separate 4x4 matrices. A little background info on this program, reads in two arrays, compares them and outputs the largest elements of the same index and outputs them in a separate array. I somehow cannot seem to figure out how to do this. My code is below:
Data File:
2 7 6 4
6 1 2 4
9 7 2 6
8 3 2 1
4 1 3 7
6 2 3 8
7 2 2 4
4 2 3 1
Code:
public class prog465a {
public static void main(String[] args) {
Scanner inFile = null;
try {
inFile = new Scanner(new File("prog465a.dat.txt"));
[Code] .....
PrintWriter Creates File But Doesn't Print File
Nov 7, 2014This is a college course assignment that consists of classes TotalSales and TotalSalesTest.In the main program I have created a two dimensional array to output a columnar layout with cross-totals in 4 rows and 5 columns. This program outputs sales totals by row for each sales person(1 - 4) and output by column for products(1 - 5). I have created extra elements in the array to store total for rows and columns. So far both classes compiles. The problem is that although the PrintWriter creates a notepad file, it doesn't print to it. I don't seem to understand the input and output methods completely. I finished another program similar to this using basically the same try and catch that read the file and printed out a document in notepad. Here is the code and I'll try include the input file.
import java.util.Scanner;
import java.io.*;
public class TotalSales {
private int salesPerson; //declare class variable
private int productNumber;//declare class variable
[code]....
Output CSV File With Printwriter
Feb 17, 2015You are given a file containing the names and addresses of company employees from many years ago that your manager has asked you to import into a database. You can use a CSV file and your database application to load the file, but the file your manager gave you was exported from an old, non-standard accounting system. Here is its format:
Fred|Flintstone
1212|Bedrock
Austin|Texas
Harry|Potter
1234|Hogwarts Road
[Code] .....
File And PrintWriter Objects
Aug 20, 2014If I am using the File object to read a file and PrintWriter object to write to a separate file, can I use them under one method. Or is the File one method and the PrintWriter another method?
View Replies View RelatedHow To Print Results Of Method To A File Using PrintWriter
Apr 29, 2015private static void getTablas(int num) {
//ciclos anidados
System.out.print("x");
//linea horizontal
for (int i = 1; i <= num; i++) {
System.out.printf("%3d ",i);
[Code] .....
I/O / Streams :: Generate File Tree Structure Of Mounted Unix File System
Apr 22, 2014I am creating a web application that runs on server X(unix) and it has another unix system mounted on it. I want to generate the file tree structure of this mounted unix file system and show it on to a web application so that users can select a file and move it onto this current unix machine.
I know this sounds stupid and you may want to say why cant we directly copy the file, I am doing a proof of concept and using this as a basis.
I/O / Streams :: Retrieving File Directories From A Text File?
Jun 25, 2014Let's say I have a text file and in the text file exists file directories as such:
'assets/picture1.png'
'assets/picture2.png'
And so on...
How would I then read from this text file and then create those files using 'new File()'?
Here is my code:
private void getFiles() throws IOException{
files = new File[10];
Scanner scan = new Scanner(new File("files.dat"));
int count = -1;
[Code]....
It does print out those files, but it doesn't create them.
I/O / Streams :: Get Specific Value From Txt File
Sep 22, 2014I know that it's possible to retrieve a line from a txt file but say for example my file looked like this:
staff id = 1
firstname
surname
age
staff id =2
firstname Kate
surname Hollar
age 33
staff id =3
firstname Daniel
surname Hong
age 21
It is possible to retrieve just the staff id's?
I/O / Streams :: Clear Old Text Then Add New To File
Aug 12, 2014I have a code that clear old text then add new text to text file afterthat download the file but the problem my code dose not add new text
FileInputStream fileToDownload ;
private static final int BYTES_DOWNLOAD = 1024;
response.setContentType("text/plain");
String name = request.getParameter("n");
String text = new String(request.getParameter("text").getBytes("iso-8859-1"), "UTF-8");
[Code] ....
How to clear old text then add new text to text file
I/O / Streams :: Read € Symbol In A File
Aug 25, 2014I have a problem with € symbol ... an application write a String content on the file system with following code:
out = new FileOutputStream(strPath + "import.xml");
out.write(trp.getTrpXMLModel().getBytes("ISO-8859-1"));
It's correctly wrote on the file system:
TT;Pierre-H€enri;;Orange Grove;zefezfezfez, Directeur Juridique;TT;;azdaz;01 53 33 56 87;ezfezfez;01 53 33 51 59;.....&ée&ée;;;;;;132;CORDIAL;aaa
But when the application try to read the previous file with following code:
BufferedReader in = new BufferedReader(new InputStreamReader(inStream,"ISO-8859-1"));
String line = in.readLine();
The application isn't able to properly read the symbol ... and return following line, without "€":
TT;Pierre-Henri;;Orange Grove;zefezfezfez, Directeur Juridique;TT;;azdaz;01 53 33 56 87;ezfezfez;01 53 33 51 59;.....&ée&ée;;;;;;132;CORDIAL;aaa
I/O / Streams :: Creating Hidden File
Jul 30, 2006I want to create hidden files, some sample code for doing this.
View Replies View RelatedI/O / Streams :: API To Read Metadata From MP4 File
May 13, 2012I am looking for a pure java api that can read metadata from an mp4 file, I have looked online but all apis I found are wrappers to native code. How to read mp4 with java .....
View Replies View RelatedI/O / Streams :: How To Read In A Binary File Correctly
Nov 8, 2014I have a binary file that has identifiers for the start of each record
You can see here that the record starts with 00 00 and the next record starts with 00 00 etc...
How do I read between these two points throughout the file?
RandomAccessFile database = new RandomAccessFile(databasePath, "r");
int start = 0;
int end = 0;
database.setLength(start);
database.seek(end);
The first start would be the start of the file, the next start would be the end of the first start and so on..
I'm just not sure how to put that into a loop.