Shulou(Shulou.com)05/31 Report--

Most people do not understand the knowledge points of this article, "Java file reading and writing operation method example analysis", so the editor summarizes the following content, detailed content, clear steps, and has a certain reference value. I hope you can get something after reading this article. Let's take a look at this "Java document reading and writing operation method case analysis" article.

IO of java

The Java program allows data to be transmitted to input and output devices through streams. The streams in Java are all in the java.io package, called IO (input / output) streams. According to the difference of operation data, IO stream can be divided into byte stream and character stream, and according to the different direction of data transmission, it can be divided into input stream and output stream. The program reads data from input stream and writes data to output stream. In IO packet, the input and output of byte stream is represented by java.InputStream and java.io.OutputStream respectively, and the input and output of character stream is represented by java.io.Reader and java.io.Writer respectively.

Byte stream

In the computer, no matter text, picture, audio or video, all files exist in binary mode. Byte stream is the most commonly used stream in the program, which is divided into byte input stream and byte output stream according to the direction of data transmission. In JDK, two abstract classes, InputStream and OutputStream, are provided. They are the top parent class of byte stream, and all byte input streams inherit OutputStream.

Common methods of InputStream

Int read () / / reads an octet from the input stream, converts it to an integer between 0,255, and returns the integer

Int read (byte [] b) / / reads several bytes from the input stream and saves them to the byte array specified by parameter b. The returned integer table 4 reads the number of bytes.

Int read (byte [] b byte int off,int len) / / reads several bytes from the input stream and saves them to the byte array specified by parameter b. Off specifies the starting subscript for the byte array to start saving data, and len represents the number of bytes read.

Void close () / / closes this input stream and releases all system resources associated with the stream

Common methods of OutputStream

Void write (int b) / / writes one byte to the output stream

Void write (byte [] b) / / writes all bytes of the byte array specified by parameter b to the output stream

Void write (byte [] b byte int off,int len) / / writes the len bytes from the offset off in the specified len array to the output stream

Void flush () / / refresh this output stream and force all buffered output bytes to be handwritten

Void close () / / closes this output stream and releases all system resources associated with this stream

The flush () method is used to force data from the current output stream buffer (usually in a byte array) to the target device, a process called flushing. Although the InputStream and OutputStream classes provide some methods for reading and writing data, both classes are abstract and cannot be instantiated.

Byte stream reads and writes files

Because the data in the computer is basically saved in the file on the hard disk, when operating the file, the data is read from the file and written to the file. FileInputStream and File Output Stream are two classes for read and write operations. Because reading data from a file is a repetitive operation, continuous reading of the data needs to be achieved through circular statements.

Package IO; import java.io.FileInputStream; public class Li01 {public static void main (String [] args) throws Exception {FileInputStream in=new FileInputStream ("test.txt"); int baked 0; while (true) {b=in.read (); if (baked colors 1) {break;} System.out.print (b+ ") } in.close ();}}

Demo result

The reason for the output is that the files on the hard disk exist in bytes, and when reading the file data, you must ensure that the files exist in the corresponding directory and are readable.

How to write data to a file package IO; import java.io.FileOutputStream; import java.io.OutputStream; import java.nio.charset.StandardCharsets; public class Li02 {public static void main (String [] args) throws Exception {OutputStream out=new FileOutputStream ("example1.txt"); String str= "study hard and make progress every day!"; byte [] b=str.getBytes (StandardCharsets.UTF_8); for (int itemositani)

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.