Java中IO操作：文件读写及错误处理-蒲公英云

Java中IO操作：文件读写及错误处理

在Java中，IO（Input/Output）操作主要包括文件的读写和相关的错误处理。

文件读写：

FileReader 和 FileWriter：这两个类是用于文本文件的读写。例如，创建一个文件并写入内容：
```java
// 创建一个文件对象
File file = new File(“example.txt”);

// 如果文件不存在，则创建它
if (!file.exists()) {

file.createNewFile();

}

// 使用FileWriter写入内容
try (FileWriter writer = new FileWriter(file)) {

String content = "This is an example";
writer.write(content);

} catch (IOException e) {

System.out.println("Error occurred while writing to file: " + e.getMessage());

}

BufferedReader 和 PrintWriter：这些类用于处理二进制文件。例如，读取和写入二进制数据：
```java
try (FileInputStream fis = new FileInputStream(“example.bin”);
```
BufferedReader br = new BufferedReader(new InputStreamReader(fis)))) {
```
String line;
while ((line = br.readLine()) != null) {
```
  // 处理读到的行
  System.out.println(line);
```
}
} catch (IOException e) {
System.out.println(“Error occurred while reading file: “ + e.getMessage());
}

OutputStream 和 InputStream：这些类用于处理数据，但不直接操作文件。例如，写入和读取字节：

try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
    ByteArrayInputStream bis = new ByteArrayInputStream("Hello, World!".getBytes())) {
  byte[] bytes = bis.readAllBytes();
  System.out.println("Read bytes: " + new String(bytes)));
  bos.write("This will be appended.".getBytes());
  byte[] appendedBytes = bos.toByteArray();
  System.out.println("Appended bytes: " + new String(appendedBytes)));
} catch (IOException e) {
  System.out.println("Error occurred while reading or writing bytes: " + e.getMessage());
}
}

错误处理：

try-catch 语句：用于捕获和处理可能抛出的异常。
IOException：Java中所有输入/输出操作可能会抛出此类异常。

示例：

import java.io.*;
// 文件读写时可能出现的错误
class FileOperationError extends IOException {
    public FileOperationError(String message) {
        super(message);
    }
}
try {
    // 创建一个文件对象
    File file = new File("example.txt");
    // 试图写入内容，可能会抛出FileNotFoundException
    try (FileWriter writer = new FileWriter(file)) {
        String content = "This is an example";
        writer.write(content);
    } catch (IOException e) {
        System.out.println("Error occurred while writing to file: " + e.getMessage());
        throw new FileOperationError("Failed to write to file due to I/O error", e);
    }
    // 试图读取文件，可能会抛出FileNotFoundException
    try (BufferedReader reader = new BufferedReader(new FileReader(file)))) {
        String line;
        while ((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    } catch (IOException e) {
        System.out.println("Error occurred while reading from file: " + e.getMessage());
        throw new FileOperationError("Failed to read from file due to I/O error", e);
    }
} catch (FileOperationError e) {
    System.out.println(e.getMessage());
    // 如果需要，可以在此处进一步处理错误
}