#fileinputstream

Working with Microsoft Excel in Selenium

Excel provides huge number of capabilities, we can make multiple use out of it like storing data, maintenance, calculations, retrieval, etc. We can use the same capabilities of Excel in Selenium with the help of programming language like Java.

In this post I will be sharing how we can use excel with the help of a class example which can be directly used in any project as a Utility. I will be…

original source : http://tutorials.jenkov.com/java-io/fileinputstream.html

The FileInputStream class makes it possible to read the contents of a file as a stream of bytes. The FileInputStream class is a subclass of InputStream. This means that you use the FileInputStream as an InputStream (FileInputStream behaves like an InputStream).

FileInputStream Example

Here is a simple FileInputStream example:

InputStream input = new FileInputStream("c:\\data\\input-text.txt"); int data = input.read(); while(data != -1) {  //do something with data...  doSomethingWithData(data);  data = input.read(); } input.close();

Note: The proper exception handling has been skipped here for the sake of clarity. To learn more about correct exception handling, go to Java IO Exception Handling.

FileInputStream Constructors

The FileInputStream class has a three different constructors you can use to create a FileInputStreaminstance. I will cover the first two here.

The first constructor takes a String as parameter. This String should contain the path in the file system to where the file to read is located. Here is a code example:

String path = "C:\\user\\data\\thefile.txt"; FileInputStream fileInputStream = new FileInputStream(path);

Notice the path String. It needs double backslashes (\\) to create a single backslash in the String, because backslash is an escape character in Java Strings. To get a single backslash you need to use the escape sequence \\.

On unix the file path could have looked like this:

String path = "/home/jakobjenkov/data/thefile.txt";

Notice the use of the for-slash (the normal slash character) as directory separator. That is how you write file paths on unix. Actually, in my experience Java will also understand if you use a / as directory separator on Windows (e.g. c:/user/data/thefile.txt), but don't take my word for it. Test it on your own system!

The second FileInputStream constructor takes a File object as parameter. The File object has to point to the file you want to read. Here is an example:

String path = "C:\\user\\data\\thefile.txt"; File   file = new File(path); FileInputStream fileInputStream = new FileInputStream(file);

Which of the constructors you should use depends on what form you have the path in before opening the FileInputStream. If you already have a String or File, just use that as it is. There is no particular gain in converting a String to a File, or a File to a String first.

read()

The read() method of a FileInputStream returns an int which contains the byte value of the byte read. If the read() method returns -1, there is no more data to read in the FileInputStream, and it can be closed. That is, -1 as int value, not -1 as byte value. There is a difference here!

You use the read() method just like the read() method of an InputStream.

read(byte[])

Being an InputStream the FileInputStream also has two read() methods which can read data into a bytearray. You can read more about them in my tutorial about the InputStream (see link elsewhere in this text).

close()

original source : http://tutorials.jenkov.com/java-io/files.html

Files are a common source or destination of data in Java applications. Therefore this text will give you a brief overview of working with files in Java. It is not the intention to explain every technique in detail here, but rather to provide you with enough knowledge to decide on a file access method. Separate pages will describe each of these methods or classes in more detail, including examples of their usage etc.

Reading Files via Java IO

If you need to read a file from one end to the other you can use a FileInputStream or a FileReaderdepending on whether you want to read the file as binary or textual data. These two classes lets you read a file one byte or character at a time from the start to the end of the file, or read the bytes into an array of byte or char, again from start towards the end of the file. You don't have to read the whole file, but you can only read bytes and chars in the sequence they are stored in the file.

If you need to jump around the file and read only parts of it from here and there, you can use aRandomAccessFile.

If you need to jump around the file and read only parts of it from here and there, you can use aRandomAccessFile.

Writing File via Java IO

If you need to write a file from one end to the other you can use a FileOutputStream or a FileWriterdepending on whether you need to write binary data or characters. You can write a byte or character at a time from the beginning to the end of the file, or write arrays of byte and char. Data is stored sequentially in the file in the order they are written.

If you need to skip around a file and write to it in various places, for instance appending to the end of the file, you can use a RandomAccessFile.

Random Access to Files via Java IO

As I have already mentioned, you can get random access to files with Java IO via the RandomAccessFileclass.

Random access doesn't mean that you read or write from truly random places. It just means that you can skip around the file and read from or write to it at the same time in any way you want. No particular access sequence is enforced. This makes it possible to overwrite parts of an existing file, to append to it, delete from it, and of course read from the file from wherever you need to read from it.

File and Directory Info Access

New Post has been published on http://heapload.com/computer-science/io-in-java

IO in Java

IO in Java

Java has very optimized and efficient packages for IO (Input and Output) operations. Java uses concept of stream (packages of data/information) for input and output tasks that are effective and supports many data types.

For reading data/information, Java invokes InputStream, and for writing, it uses OutputStream objects.

Code Examples:

Byte Streams

Java byte stream is one the most common approaches for Input and Output operations. This method converts information in the form of 8-bit bytes packages and then transfer them to the destination.

package java.examples; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; /** * * @author heapload.com */ public class byteStreamExample public static void main(String args[]) throws IOException FileInputStream input = null; FileOutputStream output = null; try input = new FileInputStream("a.txt"); output = new FileOutputStream("b.txt"); int counter; while ((counter = input.read()) != -1) output.write(counter); finally if (input != null) input.close(); if (output != null) output.close();

java-byte-stream

Procedure:

Create a new class and name it as byteStreamExample.java

Make two objects for FileInputStream and FileOutputStream with file name.

Iterate the FileInputStream object until it returns -1 as end of file.

Write all the stream information into FileOutputStream object.

Finally, close both the streaming objects.

Character Streams

Java character stream supports 16-bit (twice than byte streams) Unicode streams. This method converts information in the form of 16-bit Unicode packages and then transfer them to the destination. Like java byte streams, it has FileReader and FileWriter classes for IO purpose.

java-byte-stream-and-character-stream-comparision

import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; /** * * @author heapload.com */ public class characterStreamExample public static void main(String args[]) throws IOException FileReader in = null; FileWriter out = null; try in = new FileReader("a.txt"); out = new FileWriter("b.txt"); int counter; while ((counter = in.read()) != -1) out.write(counter); // 16-bit unicode stream (twice than byte stream) finally if (in != null) in.close(); if (out != null) out.close();

java-character-stream

Procedure:

Create a new class and name it as characterStreamExample.java

Make two objects for FileReader and FileWriter with file name.

Iterate the FileReader object until it returns -1 as end of file.

Write all the stream information into FileWriter object.

Finally, close both the streaming objects.

Read Complete File Once

If the file is small, then you can also avoid iterating InputStream object with this simple approach.

import java.io.File; import java.io.FileInputStream; /** * * @author heapload.com */ public class readFileOnce public static void main(String args[]) try File file = new File("a.txt"); FileInputStream fis = new FileInputStream(file); byte[] data = new byte[(int) file.length()]; fis.read(data); fis.close(); String str = new String(data, "UTF-8"); catch (Exception ex) System.out.println("Error In File Reading" + ex.toString());

java-read-file-once

Procedure:

Create a new class and name it as readFileOnce.java

Make two objects for File and FileInputStream.

Make a byte array with the size of the source file.

Write all the stream information once into FileInputStream object.

IO in Java Java has very optimized and efficient packages for IO (Input and Output) operations. Java uses concept of stream (packages of data/information) for input and output tasks that are effective and supports many data types. For reading data/information, Java invokes InputStream, and for writing, it uses OutputStream objects. Code Examples: Byte Streams Java byte stream is one the most…

How to: getResourceAsStream() vs FileInputStream

getResourceAsStream() vs FileInputStream

I was trying to load a file in a webapp, and I was getting a FileNotFound exception when I used FileInputStream. However, using the same path, I was able to load the file when I did getResourceAsStream(). What is the difference between the two methods, and why does one work while the other doesn’t?

Answer: getResourceAsStream() vs FileInputStream

FileInpu…