IO (Input Output) stream ___ character stream, byte stream

I. Overview of IO flow------ for manipulating data

IO streams are used to process data transfer between devices;

Java operation of data is through the flow of the way;

Java is used to manipulate the flow of objects are in the IO package;

The flow is divided into: byte Stream (Universal) and character stream, by flow direction: input stream and output stream.

Abstract base class for byte stream:

　　　InputStream, OutputStream

Abstract base class for character streams:

　　Reader, Writer

Note: The subclass names derived from these four classes are the suffixes whose parent class name is the child class name.

such as: InputStream sub-class FileInputStream; reader's subclass Filereaderstream.

Two

Two base classes for byte stream:

InputStream, OutputStream

Two base classes for character streams: (specialized in text and data)

Reader, Writer

--------->>> Character Stream

First, the operation of the main file to demonstrate

Requirements: On the hard disk, create a file and write some text data

Found a writer subclass object specifically for manipulating files. FileWriter. The suffix name is the parent class name. The prefix is the function of the stream object.

　　

Creates a FileWriter object that must be explicitly manipulated when initialized;

And the file will be created to the specified directory, if the directory has a file with the same name, the file is overwritten;

In fact, the step is to specify the destination of the data to be stored:

　　　　　　　　　　　　　　FileWriter fw = new FileWriter("demo.txt");

Call the Write method to write the string to the stream:

Fw. writer ("abcdef");

Refreshes the buffered data in the stream object and brushes the data to the destination:

Fw. Flush ();

Closes the stream resource, but flushes the internal buffer's data before closing, flushing the data to the destination.

and flush difference: After flush refreshes, the stream can continue to be used, and when close refreshes, the stream is closed:

Fw. Close ();

How IO exceptions are handled:

Please look at the code:

ImportJava.io.*; CALSS Filewriterdemo { Public Static voidMain (string[] args) {FileWriter fw=NULL; Try{FW=NewFileWriter ("Demo.txt"); Fw.write ("SAFDASF"); }catch(IOException) {
System.out.println ("Catch:" +e.tostring ());
}
　　　　finally {
　　　　　　Try {
if (fw!=null)
Fw.close ();
} catch(IOException) {
System.out.println ("Catch:" +e.tostring ());
}
}
}
}

　　

Continuation of the document:

Pass a true parameter, which means that the existing file is not overwritten and the data is resumed at the end of the existing file:

FileWriter FW = new FileWriter ("Demo.txt", true);

Read the text file:

　　　Way One:

　　　　　　Creates a file read stream object, associated with a file of the specified name;

To ensure that the file is already present, an exception filenotfoundexception occurs if it does not exist.

FileReader fw = new FileReader ("Demo.txt");

Call the Read method that reads the Stream object:

Read (): reads one character at a time and automatically reads it down.

while ((ch = fr.read ())! = -1) {

System.out.println ("ch=" + (char) ch);

}

　　Way two:

FileReader fw = new FileReader ("Demo.txt");

/* Defines an array of characters for storing read characters;

The read (char[]) returns the number of characters */:

　　　　　　　　　char[] buf = new char[1024];

int num = 0;

while ((num=fr.read (buf)) ! =-1) {

System.out.println (New String (buf, 0, num));

}

Little exercise: Read a. java file and print it on the console.

　Copy text file:

Copy the C drive one file text to the D drive:

The principle of replication is to store the file data from the C drive in a file on the D drive.

Steps:

1. Create a file in the D drive to store the data in the C drive file.

2. Define read stream and C-Drive file association;

3, through continuous reading and writing to complete the data storage;

4. Close Resources

A copy class that implements the replication feature:

1  Public Static voidCopy () {2FileWriter FW =NULL;3FileReader FR =NULL;4   Try {5FW =NewFileWriter ("Demo_copy.txt");6FR =NewFileReader ("Demo.java");7      Char[] buf =New Char[1024];8      intLen = 0;9       while(len = Fr.read (BUF))! =-1) {TenFw.write (buf, 0, Len); One      } A}Catch(IOException e) { -        Throw NewRuntimeException ("Read and Write Failed"); -     } the     finally { -         if(FR! =NULL) -           Try { - fr.close (); +}Catch(IOException e) { -  +            } A           if(FW! =NULL) at           Try { - fw.close (); -}Catch(IOException e) { -  -            } -     } in}

　　　　

IO (Input Output) stream ___ character stream, byte stream