File Handling in Java

A stream (data) is a sequence of bytes that flow from source to destination.

• We can also say that stream is an abstraction either produce or consume information.

Data may be available for reading or writing in library.                                                                                                                               In a program, we read information from input stream and write information to an output stream.

• Package java.io.* contain many classes that allow us to define various stream with particular characteristics.

I/O Streams                                                                                         

• Byte stream: Handle I/O of raw binary data.
• Character stream:   Handle I/O of character data(16 bit    unicode)
• Buffered stream:  Optimize I/O
• Object Stream: Handle binary I/O of objects.
• Data Stream: Handle binary I/O of primitive data type.

 

                                                                                                                                                                                                                                                                                                                                                 Reading and Writing Files:

As described earlier, A stream can be defined as a sequence of data. The InputStream is used to read data from a source and the OutputStream is used for writing data to a destination.

Here is a hierarchy of classes to deal with Input and Output streams.

The two important streams are FileInputStream and FileOutputStream, which would be discussed in this tutorial:

FileInputStream:

This stream is used for reading data from the files. Objects can be created using the keyword new and there are several types of constructors available.

Following constructor takes a file name as a string to create an input stream object to read the file.:

InputStream f = new FileInputStream("C:/java/hello");

Following constructor takes a file object to create an input stream object to read the file. First we create a file object using File() method as follows:

File f = new File("C:/java/hello"); 

InputStream f = new FileInputStream(f);

FileOutputStream:

FileOutputStream is used to create a file and write data into it. The stream would create a file, if it doesn't already exist, before opening it for output.

Here are two constructors which can be used to create a FileOutputStream object.

Following constructor takes a file name as a string to create an input stream object to write the file:

OutputStream f = new FileOutputStream("C:/java/hello") 

Following constructor takes a file object to create an output stream object to write the file. First, we create a file object using File() method as follows:

File f = new File("C:/java/hello"); 

OutputStream f = new FileOutputStream(f);