File and IO operation skills in Java

In Java programming, it is often necessary to perform IO operations on files. File IO operations involve operations such as reading and writing files, creating directories, and deleting files. This article will introduce some common file IO operation techniques and how to use them in Java programs.

1. File path

To operate files and directories in Java, you need to provide the file path. File paths can be divided into absolute paths and relative paths. An absolute path is the full path to the file in the file system, starting with the root directory. A relative path is the path to a file relative to the current working directory.

The file path separator in Java is "/". "" represents an escape character in Java and will not be treated as part of the path.

Examples are as follows:

String absolutePath = "C:/users/Administrator/test.txt";
String relativePath = "src/test.txt";

2. Create a directory

In Java, you can use the File class to create a directory. When the file does not exist, the directory is automatically created, otherwise it is not created.

You can use the mkdir() method to create a single-level directory, or the mkdirs() method to create a multi-level directory. When the directory is created successfully, the method returns true. Otherwise, return false.

The example is as follows:

File dir = new File("C:/users/Administrator/testDirectory");
if (!dir.exists()) {

dir.mkdirs();

}

3. Read and write files

In Java, you can use the File class to read and write files. Reading and writing files requires the use of I/O streams. When reading a file, you need to use the FileReader class or the BufferedReader class to read data. When writing a file, you need to use the FileWriter class or the BufferedWriter class to write data.

Read file example:

try(BufferedReader reader = new BufferedReader(new FileReader("src/test.txt"))){

String line;
while((line = reader.readLine()) != null) {
    System.out.println(line);
}

} catch(IOException e ) {

e.printStackTrace();

}

Writing file example:

try(BufferedWriter writer = new BufferedWriter(new FileWriter("src/test.txt"))){

writer.write("hello, world!");

} catch(IOException e) {

e.printStackTrace();

}

4. Delete files

In Java, you can use the File class to delete files or directories. To delete a file, you need to call the delete() method, and to delete a directory, you need to call the deleteDir() method.

The example is as follows:

File file = new File("src/test.txt");
if (file.exists()) {

file.delete();

}

5. Summary

In Java programming, file IO operation is a basic and essential technology. This article introduces common techniques such as file paths, creating directories, reading and writing files, and deleting files. I hope it can help Java developers.

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