Master file operation skills in Java development: implement data persistence function

In the Java development process, file operations are a very common and important part. Whether it is reading configuration files, storing user data, or exporting reports and log records, file operations are indispensable skills. This article will share some file operation techniques to achieve data persistence.

1. File reading and writing
In Java, you can use the File class to create, delete, rename, and obtain file attributes and other operations. For reading and writing files, you can use FileReader, FileWriter, BufferedReader, BufferedWriter and other classes to achieve. The following is a simple example:

import java.io.*;

public class FileOperationExample {
    public static void main(String[] args) {
        try {
            // 文件写入
            FileWriter writer = new FileWriter("data.txt");
            writer.write("Hello World!");
            writer.close();

            // 文件读取
            FileReader reader = new FileReader("data.txt");
            BufferedReader br = new BufferedReader(reader);

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

            br.close();
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

In this example, we first use FileWriter to write a string to a file named "data.txt". Then, use FileReader and BufferedReader to read the contents of the file and print the contents line by line. Finally, remember to close the associated file stream to free up resources.

2. CSV file operation
CSV (Comma-Separated Values) format is a common file format, usually used to store tabular data. In Java, you can use classes such as CSVReader and CSVWriter to read and write CSV files. The following is an example:

import com.opencsv.CSVReader;
import com.opencsv.CSVWriter;
import java.io.*;

public class CSVFileOperationExample {
    public static void main(String[] args) {
        try {
            // CSV文件写入
            CSVWriter writer = new CSVWriter(new FileWriter("data.csv"));

            String[] record1 = {"John", "Doe", "35"};
            String[] record2 = {"Jane", "Smith", "28"};
            String[] record3 = {"Tom", "Lee", "42"};

            writer.writeNext(record1);
            writer.writeNext(record2);
            writer.writeNext(record3);

            writer.close();

            // CSV文件读取
            CSVReader reader = new CSVReader(new FileReader("data.csv"));

            String[] line;
            while ((line = reader.readNext()) != null) {
                System.out.println(String.join(", ", line));
            }

            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

In this example, we use the third-party library opencsv to operate CSV files. First, use CSVWriter to write three records to a CSV file named "data.csv", using commas as the separator between fields. Then, use the CSVReader and readNext() methods to read each line in the file, and finally print the fields of each line in comma-separated form.

3. Serialization and Deserialization
Java provides object serialization (Serialization) and deserialization (Deserialization) mechanisms, which can convert objects into byte streams for storage, or from characters Throttle revert to object. In this way, objects can be stored or transferred in the form of files. The following is an example:

import java.io.*;

class Person implements Serializable {
    private static final long serialVersionUID = 1L;
    String name;
    int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

public class SerializationExample {
    public static void main(String[] args) {
        try {
            // 对象序列化
            Person person = new Person("John Doe", 35);
            FileOutputStream fileOut = new FileOutputStream("person.ser");
            ObjectOutputStream out = new ObjectOutputStream(fileOut);
            out.writeObject(person);
            out.close();
            fileOut.close();

            // 对象反序列化
            FileInputStream fileIn = new FileInputStream("person.ser");
            ObjectInputStream in = new ObjectInputStream(fileIn);
            Person deserializedPerson = (Person) in.readObject();
            in.close();
            fileIn.close();

            System.out.println("Name: " + deserializedPerson.name);
            System.out.println("Age: " + deserializedPerson.age);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

In this example, we define a class named Person that implements the Serializable interface so that the class can be serialized. We then created a Person object and serialized it into a file named "person.ser". Next, we deserialize the Person object from the file and print out the object's properties.

In actual development, file operations are very common operations. By mastering skills such as file reading and writing, CSV file operations, serialization and deserialization, we can easily implement the data persistence function, thereby realizing richer application scenarios. I hope this article will be helpful to your file operations in Java development.

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