Java IO - 读写文件的所有操作方式

迈不过友情╰ 2022-10-17 11:08 113阅读 0赞

参考：

*  [读文件][Link 1]
 *  [写文件][Link 2]

import org.junit.Test;
    
    import java.io.*;
    import java.nio.ByteBuffer;
    import java.nio.channels.FileChannel;
    import java.nio.file.Files;
    import java.nio.file.Path;
    import java.nio.file.Paths;
    import java.util.stream.Stream;
    
    public class IODemo { 
    
        String filePath = "fair-scheduler.xml";
    
        @Test
        public void readWriteFileJava11() { 
            String content  = "hello world !!";
            Files.writeString(Path.of(filePath), content);
        }
        @Test
        public void writeFileJava11() { 
            String actual = Files.readString(Path.of(filePath));
            System.out.println(actual);
        }
    
        @Test
        public void readFileJava8() throws IOException { 
            Stream<String> stream = Files.lines(Paths.get(filePath));
            stream.forEach(s -> System.out.println(s));
        }
    
        // Java 8中编写文件的首选方式
        @Test
        public void writeFileNio() throws IOException { 
            String fileContent = "Hello Learner !!";
    
            RandomAccessFile stream = new RandomAccessFile(filePath, "rw");
            FileChannel channel = stream.getChannel();
    
            byte[] strBytes = fileContent.getBytes();
            ByteBuffer buffer = ByteBuffer.allocate(strBytes.length);
    
            buffer.put(strBytes);
            buffer.flip();
            channel.write(buffer);
    
            stream.close();
            channel.close();
        }
    
        @Test
        public void readFileJava7() throws IOException { 
            String context = new String(Files.readAllBytes(Paths.get(filePath)));
            System.out.println(context);
        }
        @Test
        public void writeFileJava7() throws IOException { 
            String fileContent = "Hello Learner !!!";
            Files.write(Paths.get(filePath), fileContent.getBytes());
        }
    
        @Test
        public void readFileJava6() { 
            StringBuilder context = new StringBuilder();
            try (BufferedReader br = new BufferedReader(new FileReader(filePath))) { 
                String currentLine = null;
                while ((currentLine = br.readLine()) != null) { 
                    context.append(currentLine).append("\r\n");
                }
                System.out.println(context);
            } catch (IOException e) { 
                e.printStackTrace();
            }
        }
    
        @Test
        public void bufferWriteFile() throws IOException { 
            String fileContent = "Hello Learner !!!";
            BufferedWriter bw = new BufferedWriter(new FileWriter(filePath));
            bw.write(fileContent);
            bw.close();
        }
    
        // FileWriter直接写入文件（性能较低），仅在写入次数较少时才应使用。
        @Test
        public void fileWriteFile() throws IOException { 
            String fileContext = "Hello Learner !!!";
            FileWriter fw = new FileWriter(filePath);
            fw.write(fileContext);
            fw.close();
        }
    
        // 使用PrintWriter写格式化的文本文件
        @Test
        public void printWriter() throws IOException { 
            String fileContext = "Hello Learner!!!";
            PrintWriter pw = new PrintWriter(new FileWriter(filePath));
            pw.printf("Blog name is %s", "tom");
            pw.close();
        }
    
        //使用FileOutputStream到二进制数据写入一个文件。FileOutputStream用于写入原始字节流，例如图像数据。要写入字符流，请考虑使用FileWriter.
        @Test
        public void fileOutputStringWriteFile() throws IOException { 
            String fileContext = "Hello Learner!!!";
            FileOutputStream fos = new FileOutputStream(filePath);
            byte[] bytes = fileContext.getBytes();
            fos.write(bytes);
            fos.close();
        }
    
        // 将原始 Java 数据类型写入输出流。然后，应用程序可以使用数据输入流将数据读回。
        @Test
        public void dataOutputStreamWriteFile() throws IOException { 
            String fileContent = "Hello Learner !!";
    
            FileOutputStream outputStream = new FileOutputStream(filePath);
            DataOutputStream dataOutStream = new DataOutputStream(new BufferedOutputStream(outputStream));
            dataOutStream.writeUTF(fileContent);
    
            dataOutStream.close();
        }
    }

[Link 1]: https://howtodoinjava.com/java/io/java-read-file-to-string-examples/
[Link 2]: https://howtodoinjava.com/java/io/java-write-to-file/