Reading and Writing files

13,262 8TB

The program below simply reads a file called FileTest1.java(itself) and prints it to the console

Expand|Select|Wrap|Line Numbers

  
import java.util.Scanner;

import java.io.*;

class FileTest1 {

 public static void main(String args[]) {

  Scanner inputFile = null;

  try {

   inputFile = new Scanner(new File("FileTest1.java"));

   while(inputFile.hasNext()) {

    System.out.println(inputFile.next());

   }
 
  }

  catch(FileNotFoundException fNFE) {

   System.out.println("The file was not found");

  }

  finally {

   inputFile.close();

  }
 
 } 
 
}

Two methods of the Scanner class were used here hasNext and next.
You should be able to see what these methods are doing here if not then you can check with the Scanner page on sun's Java API.
This is the recommended way of reading a file these days.

To write to a file, use the FileWriter class wrapped in a BufferedWriter

Expand|Select|Wrap|Line Numbers

  
public static void writeFile(String fileName) {

 BufferedWriter br = null;

 try {

  br = new BufferedWriter(new FileWriter(fileName));

  String[] semiFinals = {"Australia", "West Indies", "South Africa", "Sri Lanka"};

  for(String s : semiFinals) {

   br.write(s);

   br.write(System.getProperty("line.separator"));

  }

  br.close();

 }

 catch(IOException iO) {

  System.out.println("The file could not be created/opened/closed");

 }

}

Notice the use of System.getProperty("line.separator"); to write a return
This method of opening a file overrides the data that was on the file.
To open the file in append mode, simply use

Expand|Select|Wrap|Line Numbers

br = new BufferedWriter(new FileWriter(fileName, true));

These approaches should not be used for manipulating .doc, pdf, xls e.t.c Instead one should use more specific packages

Mar 27 '07 #1

Subscribe Post Reply

16835

JosAH

11,448

Expert 8TB

I don't want to exhibit myself as a nitpicker but why don't you just simply use
a BufferedReader for this instead of a Scanner. BufferedReaders are available
in Java 1.4 and before while those Scanners are only available starting from
Java 1.5 and up. BufferedReaders are much simpler too.

kind regards,

Jos (<--- nitpicker ;-)

Mar 29 '07 #2

r035198x

13,262

8TB

I don't want to exhibit myself as a nitpicker but why don't you just simply use
a BufferedReader for this instead of a Scanner. BufferedReaders are available
in Java 1.4 and before while those Scanners are only available starting from
Java 1.5 and up. BufferedReaders are much simpler too.

kind regards,

Jos (<--- nitpicker ;-)

And for those who prefer the nitpicker's advice

Expand|Select|Wrap|Line Numbers

  
import java.io.*;

class FileTest1 {

public static void main(String args[]) {

BufferedReader inputFile = null;

try {

inputFile = new BufferedReader (new FileReader("FileTest1.java"));

while((String line = inputFile.readLine()) != null) {

         System.out.println(line);

}
 
}

catch(FileNotFoundException fNFE) {

System.out.println("The file was not found");

}

catch(IOException iO) {

    System.out.println("IO error");

}

finally {

inputFile.close();

}
 
} 
 
}

Mar 29 '07 #3

JosAH

11,448

Expert 8TB

And for those who prefer the nitpicker's advice

:-)

kind regards,

Jos

ps. while I'm at it, other IOExceptions can be thrown too you know ;-)

Mar 29 '07 #4

r035198x

13,262

8TB

:-)

kind regards,

Jos

ps. while I'm at it, other IOExceptions can be thrown too you know ;-)

But of course Jos.

At which point I will now have to edit the post.

Mar 29 '07 #5

JosAH

11,448

Expert 8TB

But of course Jos.

At which point I will now have to edit the post.

I'm sorry for stirring this all up; I'm a nasty nitpicker ;-)

kind regards,

Jos

Mar 29 '07 #6

saraali

hello every body

I need a help please help me if you can
what functions can we use to send multimedia (vedio,oudio,imeges) using java through socket .

send any thing about this subject to my e-mail : <email removed:Against site rules>
thanks ................

Mar 31 '07 #7

JosAH

11,448

Expert 8TB

hello every body

I need a help please help me if you can
what functions can we use to send multimedia (vedio,oudio,imeges) using java through socket .

send any thing about this subject to my e-mail : dreams294@hotmail.com
thanks ................

Please start you own topic for your question; don't pollute anyone else's topic.

kind regards,

Jos

Mar 31 '07 #8

quadelirus

I don't want to exhibit myself as a nitpicker but why don't you just simply use
a BufferedReader for this instead of a Scanner.

Can't the Scanner class be a better option if, for instance, someone wanted to easily extract various forms of data from the input say one structured with integers floats and strings all on the same line? Of course you CAN use the BufferedReader, but the scanner may be a better choice for an actual solution to a problem.

Just my 2c.

Apr 18 '07 #9

JosAH

11,448

Expert 8TB

Can't the Scanner class be a better option if, for instance, someone wanted to easily extract various forms of data from the input say one structured with integers floats and strings all on the same line? Of course you CAN use the BufferedReader, but the scanner may be a better choice for an actual solution to a problem.

Just my 2c.

Sure, a Scanner would be much better for that purpose, but for the purpose
shown in the article a Scanner would be overkill; that's why I was nitpicking ;-)
(and besides that, Scanners are only here with us, starting at Java 1.5)

kind regards,

Jos

Apr 18 '07 #10

jyohere

Sure, a Scanner would be much better for that purpose, but for the purpose
shown in the article a Scanner would be overkill; that's why I was nitpicking ;-)
(and besides that, Scanners are only here with us, starting at Java 1.5)

kind regards,

Jos

I want to read on a field by field basis say

Name Age DateOfBirth

Jyo 25 28-11-82
Ram 30 20-12-81

say I want to read the above file and find out the entries whose DOB is between two given dates

May 8 '07 #11

JosAH

11,448

Expert 8TB

I want to read on a field by field basis say

Name Age DateOfBirth

Jyo 25 28-11-82
Ram 30 20-12-81

say I want to read the above file and find out the entries whose DOB is between two given dates

Read the API docs for the Scanner class and use the code supplied
in this tip of the week to read all non-white space tokens. Oh, before I forget,
the FileReader or FileInputStream classes top it all off.

kind regards,

Jos

May 8 '07 #12

nomad

664

Expert 512MB

Hey a great posting would be how to use a Arraylist.
code to build arraylist
code to create output file and write arraylist
code to read input files and rebuild an Arraylist
code to display the contents on an arraylist.

This was a hard one for me to understand, and sometimes it still is.

nomad.
just my two cents.

May 8 '07 #13

JosAH

11,448

Expert 8TB

Hey a great posting would be how to use a Arraylist.
code to build arraylist
code to create output file and write arraylist
code to read input files and rebuild an Arraylist
code to display the contents on an arraylist.

This was a hard one for me to understand, and sometimes it still is.

Why don't you try it yourself? You try to write a nice concise article; post your
attempts in this forum and I for one will help you out when you're stuck. When
the article is finished you can stick it in the Articles section. deal?

kind regards,

Jos

May 8 '07 #14

nomad

664

Expert 512MB

Why don't you try it yourself? You try to write a nice concise article; post your
attempts in this forum and I for one will help you out when you're stuck. When
the article is finished you can stick it in the Articles section. deal?

kind regards,

Jos

How did I get invloved with this. Heck I'm just starting out in Java. I have only done a several projects. Two with Arraylist and I had a very very hard time doing those....I don't even know if I did those right, because the instructor has not grade them.
Besides I think the viewer would rather see ane Expert like you do it Jos.

nomad.
Maybe in a few months when I get more under my belt. I would do one for Flash or HTML...

May 8 '07 #15

JosAH

11,448

Expert 8TB

How did I get invloved with this. Heck I'm just starting out in Java. I have only done a several projects. Two with Arraylist and I had a very very hard time doing those....I don't even know if I did those right, because the instructor has not grade them.
Besides I think the viewer would rather see ane Expert like you do it Jos.

Stage fright? ;-) I promised I'd help you out and maybe during the 'making' of
the article others will join us in this forum. It could be fun. I promise I won't
'attack' you ;-) Why not give it a try? All we have to come up with now is a
nice, simple problem/project that naturally has to do with Lists.

kind regards,

Jos

May 8 '07 #16

nomad

664

Expert 512MB

Stage fright? ;-) I promised I'd help you out and maybe during the 'making' of
the article others will join us in this forum. It could be fun. I promise I won't
'attack' you ;-) Why not give it a try? All we have to come up with now is a
nice, simple problem/project that naturally has to do with Lists.

kind regards,

Jos

OK Jos...
I making a arraylist program for you It might be too long but it is one of my assignments. I could shorten it.
Anyways here is the code so far, but I'm having problem

I can not invoke the findPerson method. It should work because I have done this in the past.
I did a debug and got this error.

<terminated>EmployeeData (1) [Java Application]
<disconnected>arrayproject.EmployeeData at localhost:1253
<terminated, exit value: 0>C:\Program Files\EasyEclipse Desktop Java 1.2.1\jre\bin\javaw.exe (May 9, 2007 2:04:22 PM)

I have attached my whole project and if someone can help me that would be great..

Expand|Select|Wrap|Line Numbers

 class PersonClass {

    private String empid;

    private String lname;

    private String fname;

    private String street;

    private String city;

    private String state;

    private String zip;

    private double payrate;

    private int yearsworked;

    public PersonClass(String id) {

        empid = id;

    }

    public PersonClass(String id, String ln, String fn, String st, String ct, String se, String zp, double pr, int yw) {

        empid = id;

        lname = ln;

        fname = fn;

        street = st;

        city = ct;

        state = se;

        zip = zp;

        payrate = pr;

        yearsworked = yw;
 
    }
 
    // accessors

    public String getID() {return empid;}
 
    public String getFname() {return fname;}
 
    public String getLname() {return lname;}
 
    public String getStree() {return street;}
 
    public String getCity() {return city;}
 
    public String getState() {return state;}
 
    public String getZip() {return zip;}
 
    public double getPayrate() {return payrate;}
 
    public int getYearsworked() {return yearsworked;}
 
}
 
public class EmployeeData {

    static ArrayList<PersonClass> arlist;

    static Scanner kbd;
 
    public static PersonClass makePerson() {

        PersonClass temp = null;
 
        // prompt for data

        String id;

        String ln;

        String fn;

        String st;

        String se;

        String ct;

        String zp;

        double pr;

        int years;
 
        System.out.print("Enter ID Number ==>");

        id = kbd.next();
 
        System.out.print("Enter Last Name ==>");

        ln = kbd.next();
 
        System.out.print("Enter First Name ==>");

        fn = kbd.next();
 
        System.out.print("Enter the address==>");

        st = kbd.next();
 
        System.out.print("Enter City ==>");

        ct = kbd.next();
 
        System.out.print("Enter State ==>");

        se = kbd.next();
 
        System.out.print("Enter Zip ==>");

        zp = kbd.next();
 
        System.out.print("Enter payrate as double ==>");

        pr = kbd.nextDouble();
 
        System.out.print("Enter years worked ==>");

        years = kbd.nextInt();
 
        // make an object

        temp = new PersonClass(id, ln,fn,st,ct,se, zp, pr,years);
 
        return temp;

    }
 
    public void displayMatch() {
 
    String id_flag = "";

    Scanner kbd = new Scanner(System.in);

    System.out.println("Enter your info please ie: AB1234: ");

    id_flag = kbd.next();

    boolean notfound = true;

    for (PersonClass e : arlist) {

        String emp = e.getID();

        if (emp.equals(id_flag)) {

            System.out.println("Hello" + ("e.lname"));

            notfound = false;

        }

    }

    if (notfound == true) {

        System.out.println("Error - Employee not found");

        // back to menu?

}
 
    }//close findperson
 
    public static void main(String[] args) {

        EmployeeData emp = new EmployeeData();

        // make array list object

        arlist = new ArrayList<PersonClass>();
 
        // make a scanner

        kbd = new Scanner(System.in);
 
        int choice;

        System.out.println("Make a Section: ");

        System.out.println("1. Enter Employees ");

        System.out.println("2. Find Employees ");

        System.out.println("3. Exit this Program ");

        System.out.print("\nPlease press Enter afer each response");

        System.out.println("Enter your chose please: ");

        choice = kbd.nextInt();

        kbd.nextLine();

        if (choice == 1) { // if 1 is select go to makePerson
 
        // create people until select stop

        boolean endData = false;
 
        while (!endData) {

            PersonClass temp = makePerson();

            arlist.add(temp);

            System.out.println("Add More employees (Y/N)-->");
 
            String ans = kbd.next();
 
            if (ans.equalsIgnoreCase("N")) {

                endData = true;

            }

        }//close while loop

        if (choice == 2) { // if 2 is select go to find

            emp.displayMatch();
 
        }// close the choice==2

        if (choice == 3) {

            System.out.printf("Good bye");

        }// close the choice == 3
 
        // print out all elements of array list

        for (PersonClass idx : arlist) {

            System.out.printf("Employee Id is %n", idx.getID());

                System.out.printf("Name is %s - %s%n", idx.getFname(),idx.getLname());

                System.out.printf("Street is %s%n", idx.getStree());

                System.out.printf("City is %s%n", idx.getCity());

                System.out.printf("State is %s%n", idx.getState());

                System.out.printf("Zip Code is %s%n", idx.getZip());

                System.out.printf("Payrate is %8.2f%n", idx.getPayrate());

                System.out.printf("Years worked are %d\n", idx.getYearsworked());

                System.out.println("--------------------");

        }

    }

}

}

Thanks a bunch
nomad

May 9 '07 #17

JosAH

11,448

Expert 8TB

I created a new thread for Nomad's Article under construction so there'll be no
need anymore to hijack this thread.

kind regards,

Jos

May 10 '07 #18

JCEtajin

The program below simply reads a file called FileTest1.java(itself) and prints it to the console

Expand|Select|Wrap|Line Numbers

import java.util.Scanner;

import java.io.*;

class FileTest1 {

public static void main(String args[]) {

  Scanner inputFile = null;

  try {

   inputFile = new Scanner(new File("FileTest1.java"));

   while(inputFile.hasNext()) {

    System.out.println(inputFile.next());

   }

  }

  catch(FileNotFoundException fNFE) {

   System.out.println("The file was not found");

  }

  finally {

   inputFile.close();

  }

}

}

Two methods of the Scanner class were used here hasNext and next.
You should be able to see what these methods are doing here if not then you can check with the Scanner page on sun's Java API.
This is the recommended way of reading a file these days.

To write to a file, use the FileWriter class wrapped in a BufferedWriter

Expand|Select|Wrap|Line Numbers

public static void writeFile(String fileName) {

BufferedWriter br = null;

try {

  br = new BufferedWriter(new FileWriter(fileName));

  String[] semiFinals = {"Australia", "West Indies", "South Africa", "Sri Lanka"};

  for(String s : semiFinals) {

   br.write(s);

   br.write(System.getProperty("line.separator"));

  }

  br.close();

}

catch(IOException iO) {

  System.out.println("The file could not be created/opened/closed");

}

}

Notice the use of System.getProperty("line.separator"); to write a return
This method of opening a file overrides the data that was on the file.
To open the file in append mode, simply use

Expand|Select|Wrap|Line Numbers

br = new BufferedWriter(new FileWriter(fileName, true));

These approaches should not be used for manipulating .doc, pdf, xls e.t.c Instead one should use more specific packages

how to apply in JFileChooser?..that it can read the file that was selected.

Sep 27 '07 #19

chaarmann

785

Expert 512MB

Usually loading a whole file at once is faster than looping through it line by line. Especially if the file resides on a network device.

Here is the code:

Expand|Select|Wrap|Line Numbers

 
// check existence

File file = new File(sourceFileName);

if (! file.exists()) throw new IOException("ERROR: no such source file: " + sourceFileName);
 
// read as string

FileInputStream fileInputStream = new FileInputStream(sourceFileName);

byte data[] = new byte[fileInputStream.available()];

fileInputStream.read(data);

String content = new String(data);
 
// do whatever you want with the result

System.out.println("File contains:" + content);

Oct 30 '08 #20

Similar topics

Reading PDF Files with PHP

by: dunnm | last post by:

This is probably a more appropriate location to post this question. I should have know that since I've found most of the other PHP/PDF information contained in this group. Here's my issue...I...

PHP

Reading/Writing directly to/from a device in MSWindows

by: Benjamin de Waal | last post by:

Hey all, I'm trying to figure out how to directly write to a device in Windows. Basically, what I'm wanting to do is create an image of a device (specifically, a CompactFlash card that uses a...

C / C++

reading and writing a file

by: John Salerno | last post by:

I wrote this code just to experiment with writing to and reading from a file. It seems to work fine when writing, but when reading the file, it only prints the filepath to the screen, not the file...

C# / C Sharp

reading and writing to binary files

by: Robert Reijntjes | last post by:

Hi, I need to read/write data from/to binary files that have an already defined. This means I can't define classes with the attribute. The files also have arrays with variable length. This...

C# / C Sharp

Problem reading/writing files

by: smeenehan | last post by:

This is a bit of a peculiar problem. First off, this relates to Python Challenge #12, so if you are attempting those and have yet to finish #12, as there are potential spoilers here. I have five...

Python

problem reading/writing structures from and to files

by: arne.muller | last post by:

Hello, I've come across some problems reading strucutres from binary files. Basically I've some strutures typedef struct { int i; double x; int n; double *mz;

C / C++

Reading Fortran Data

by: Tyler | last post by:

Hello All: After trying to find an open source alternative to Matlab (or IDL), I am currently getting acquainted with Python and, in particular SciPy, NumPy, and Matplotlib. While I await the...

Python

Efficiently reading a string from a specific point in a file

by: random guy | last post by:

Hi, I'm writing a program which creates an index of text files. For each file it processes, the program records the start and end positions (as returned by tellg()) of sections of interest,...

C / C++

Preserving Chinese Characters when reading and writing text

by: Clive Green | last post by:

Hello peeps, I am using PHP 5.2.2 together with MP3_Id (a PEAR module for reading and writing MP3 tags). I have been using PHP on the command line (Mac OS X Unix shell, to be precise), and am...

PHP

how to trap an error reading CDrom

by: Guido Geurs | last post by:

I'm writing a program that list the contents of a CDrom and also the contents of the ZIP files. When there is a bad Zip file on the CD, the program keeps traying to reed the file and after +- 50...

Visual Basic 4 / 5 / 6

Wordpress or something else?

by: Faith0G | last post by:

I am starting a new it consulting business and it's been a while since I setup a new website. Is wordpress still the best web based software for hosting a 5 page website? The webpages will be...

Content Management Systems

Access Europe: Command bars, the Access Shortcut Tool and a simple Audit Log - Wed 3 April

by: isladogs | last post by:

The next Access Europe User Group meeting will be on Wednesday 3 Apr 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome former...

General

One-click Importing Excel Data into a*Database

by: ryjfgjl | last post by:

In our work, we often need to import Excel data into databases (such as MySQL, SQL Server, Oracle) for data analysis and processing. Usually, we use database tools like Navicat or the Excel import...

Microsoft Excel

Easy Steps to Fix "Canon Printer Won't Connect to WiFi Network"

by: taylorcarr | last post by:

A Canon printer is a smart device known for being advanced, efficient, and reliable. It is designed for home, office, and hybrid workspace use and can also be used for a variety of purposes. However,...

General

How to turn on java script in a villaon keypad mobile phone

by: Charles Arthur | last post by:

How do i turn on java script on a villaon, callus and itel keypad mobile phone

Java

Migrating Website to Cloud - Emmanuel Katto

by: emmanuelkatto | last post by:

Hi All, I am Emmanuel katto from Uganda. I want to ask what challenges you've faced while migrating a website to cloud. Please let me know. Thanks! Emmanuel

General

Navigating the Data Structures and Algorithms (DSA)

by: BarryA | last post by:

What are the essential steps and strategies outlined in the Data Structures and Algorithms (DSA) roadmap for aspiring data scientists? How can individuals effectively utilize this roadmap to progress...

Algorithms / Advanced Math

Looking to do Android software development, any suggestions? Is flutter better?

by: nemocccc | last post by:

hello, everyone, I want to develop a software for my android phone for daily needs, any suggestions?

General

Is that possible of reading the .csv file in column wise and the column have different lengths ?

by: Sonnysonu | last post by:

This is the data of csv file 1 2 3 1 2 3 1 2 3 1 2 3 2 3 2 3 3 the lengths should be different i have to store the data by column-wise with in the specific length. suppose the i have to...

C / C++