How to use I/O streams in Java to read and write files?

2 years ago
Ava Mitchell
2 minutes

In Java, reading and writing files using IO streams mainly involves the following classes and interfaces:

  1. FileInputStream and FileOutputStream are used to read and write files as streams of bytes, operating on a byte-by-byte basis.
  2. FileReader and FileWriter: used for reading and writing files in character streams, reading and writing is done on a character-by-character basis.
  3. BufferedReader and BufferedWriter: used to provide a buffering mechanism that can enhance reading and writing efficiency.
  4. InputStreamReader and OutputStreamWriter: used to convert byte streams into character streams for reading and writing character streams.

Here are some common examples of code for reading and writing files:

  1. Reading and writing byte streams in files using FileInputStream and FileOutputStream.
import java.io.*;

public class FileIOExample {
    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("input.txt");
            FileOutputStream fos = new FileOutputStream("output.txt");

            int data;
            while ((data = fis.read()) != -1) {
                fos.write(data);
            }

            fis.close();
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
  1. Read and write character streams files using FileReader and FileWriter.
import java.io.*;

public class FileIOExample {
    public static void main(String[] args) {
        try {
            FileReader fr = new FileReader("input.txt");
            FileWriter fw = new FileWriter("output.txt");

            int data;
            while ((data = fr.read()) != -1) {
                fw.write(data);
            }

            fr.close();
            fw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
  1. Read and write files using BufferedReader and BufferedWriter.
import java.io.*;

public class FileIOExample {
    public static void main(String[] args) {
        try {
            BufferedReader br = new BufferedReader(new FileReader("input.txt"));
            BufferedWriter bw = new BufferedWriter(new FileWriter("output.txt"));

            String line;
            while ((line = br.readLine()) != null) {
                bw.write(line);
                bw.newLine(); // 写入换行符
            }

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

These sample codes only cover basic read and write file operations, additional steps such as handling exceptions and closing streams may be needed when using them.

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