Java中try-with-resources的使用详解

try (ResourceType resource = new ResourceType()) {
    // 使用资源的代码
} catch (Exception e) {
    // 异常处理
}

public interface AutoCloseable {
    void close() throws Exception;
}

public interface Closeable extends AutoCloseable {
    void close() throws IOException;
}

BufferedReader br = null;
try {
    br = new BufferedReader(new FileReader("test.txt"));
    // 业务代码
} catch (IOException e) {
    e.printStackTrace();
} finally {
    // 必须判空 + 嵌套try-catch（close()也会抛异常）
    if (br != null) {
        try {
            br.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

try (BufferedReader br = new BufferedReader(new FileReader("test.txt"))) {
    // 业务代码
} catch (Exception e) {
    e.printStackTrace();
}

try (BufferedReader br = new BufferedReader(new FileReader("test.txt"))) {
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

try (InputStream in = new FileInputStream("input.txt");
     OutputStream out = new FileOutputStream("output.txt")) {
    
    byte[] buffer = new byte[1024];
    int bytesRead;
    while ((bytesRead = in.read(buffer)) != -1) {
        out.write(buffer, 0, bytesRead);
    }
} catch (IOException e) {
    e.printStackTrace();
}

// 声明顺序：Connection → PreparedStatement → ResultSet
try (Connection conn = DriverManager.getConnection(url, user, pwd);
     PreparedStatement ps = conn.prepareStatement("SELECT * FROM user");
     ResultSet rs = ps.executeQuery()) {
    // 业务逻辑
}
// 关闭顺序：ResultSet → PreparedStatement → Connection