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Today, the editor will share with you the relevant knowledge points about the functions of Stream, File and IO of Java. The content is detailed and the logic is clear. I believe most people still know too much about this knowledge, so share this article for your reference. I hope you can get something after reading this article. Let's take a look.

Java streams (Stream), files (File), and IO (input / output)

The Java.io package contains almost all the classes needed to manipulate input and output. All of these streams represent input sources and output destinations.

Streams in the Java.io package support a variety of formats, such as basic types, objects, localized character sets, and so on.

A stream can be understood as a sequence of data. The input stream represents reading data from a source, and the output stream represents writing data to a destination.

Java provides powerful and flexible support for iPUBO, which makes it more widely used in file transfer and network programming.

Now let's talk about the most basic and stream-related functions. VPS (virtual server)

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Read console input

The console input of Java is done by System.in.

To get a character stream bound to the console, you can create a character stream by wrapping System.in in a BufferedReader (buffered stream) object.

On the right is the basic syntax for creating a BufferedReader: BufferedReader br = new BufferedReader (new InputStreamReader (System.in))

After the BufferedReader object is created, we can use the read () method to read a character from the console, or the readLine () method to read a string.

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Read multi-character input from the console

To read a character from a BufferedReader object, use the read () method, whose syntax is like right: int read () throws IOException

Each time the read () method is called, it reads a character from the input stream and returns that character as an integer value. Returns-1 when the stream ends. This method throws an IOException.

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Read strings from the console

Reading a string from standard input requires the readLine () method of BufferedReader.

Its general format is: String readLine () throws IOException

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Console output

As mentioned earlier, the output of the console is done by print () and println (). These methods are defined by the class PrintStream (output stream), and System.out is a reference to that class object.

PrintStream inherits the OutputStream class and implements the method write (). In this way, write () can also write operations using the round-trip console.

The simplest format for PrintStream definition write () is shown on the right: void write (int byteval)

This method writes the lower octet of the byteval to the stream.

Note: the write () method is used infrequently because the print () and println () methods are more convenient to use.

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Read and write files

As mentioned earlier, a stream is defined as a sequence of data. The input stream is used to read data from the source, and the output stream is used to write data to the destination.

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FileInputStream (file input stream)

This stream is used to read data from a file, and its objects can be created with the keyword new.

There are several construction methods that can be used to create objects.

You can use a file name of type string to create an input stream object to read the file: InputStream f = new FileInputStream ("C:/java/hello")

You can also use a file object to create an input stream object to read the file. We first have to use the File () method to create a file object:

File f = new File ("C:/java/hello")

InputStream f = new FileInputStream (f)

Once the InputStream object is created, you can use the following methods to read the stream or perform other stream operations.

Description of serial number method

1 public void close () throws IOException {} closes this file input stream and releases all system resources associated with this stream. Throw an IOException exception.

2 protected void finalize () throws IOException {}

This method clears the connection to the file. Be sure to call its close method when the file input stream is no longer referenced. Throw an IOException exception.

3 public int read (int r) throws IOException {} this method reads specified bytes of data from the InputStream object. Returns as an integer value. Returns the next byte of data, or-1 if it has reached the end.

4 public int read (byte [] r) throws IOException {} this method reads bytes of r.length length from the input stream. Returns the number of bytes read. Returns-1 if it is the end of the file.

5 public int available () throws IOException {} returns the number of bytes that can be read from this input stream unblocked the next time the method called on this input stream is called. Returns an integer value.

In addition to InputStream, there are some other input streams. Refer to javaInputStream for more details.

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FileOutputStream (file output stream)

This class is used to create a file and write data to the file.

If the stream does not exist before opening the file for output, the stream creates the file.

There are two constructors that can be used to create FileOutputStream objects.

Use a file name of type string to create an output stream object: OutputStream f = new FileOutputStream ("C:/java/hello")

You can also use a file object to create an output stream to write to the file. We first have to use the File () method to create a file object:

File f = new File ("C:/java/hello")

OutputStream f = new FileOutputStream (f)

After you have created the OutputStream object, you can use the following methods to write to the stream or perform other stream operations.

Description of serial number method

1 public void close () throws IOException {} closes this file input stream and releases all system resources associated with this stream. Throw an IOException exception.

2 protected void finalize () throws IOException {} this method clears the connection to the file. Be sure to call its close method when the file input stream is no longer referenced. Throw an IOException exception.

3 public void write (int w) throws IOException {} this method writes the specified bytes to the output stream.

4 public void write (byte [] w) writes the bytes of w.length length in the specified array to OutputStream.

In addition to OutputStream, there are some other output streams. Refer to javaFileOutputStream for more details.

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File and Icano (input / output)

There are also some classes about files and Ibank O that we also need to know:

-File Class (class)

-FileReader Class (class)

-FileWriter Class (class)

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Directories in Java

Create a directory:

There are two methods in the File class you can use to create folders:

The mkdir () method creates a folder, which returns true for success and false for failure. The failure indicates that the path specified by the File object already exists, or the folder cannot be created because the entire path does not already exist.

The mkdirs () method creates a folder and all its parent folders.

Note: Java automatically distinguishes the file path delimiter in UNIX and Windows by convention. If you use the delimiter (/) in the Windows version of Java, the path will still be parsed correctly.

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Read directory

A directory is actually a File object that contains other files and folders.

If you create a File object and it is a directory, calling the isDirectory () method returns true.

You can extract the list of files and folders it contains by calling the list () method on the object.

These are all the contents of the article "what are the functions of Java's Stream, File and IO?" Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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