finally块确保资源正确释放

FileInputStream fis = null;
try {
    fis = new FileInputStream("data.txt");
    int data = fis.read();
    while (data != -1) {
        System.out.print((char) data);
        data = fis.read();
    }
} catch (IOException e) {
    System.err.println("IO异常：" + e.getMessage());
} finally {
    if (fis != null) {
        try {
            fis.close();
        } catch (IOException e) {
            System.err.println("关闭流失败：" + e.getMessage());
        }
    }
}

try (FileInputStream fis = new FileInputStream("data.txt")) {
    int data = fis.read();
    while (data != -1) {
        System.out.print((char) data);
        data = fis.read();
    }
} catch (IOException e) {
    System.err.println("IO异常：" + e.getMessage());
}
// fis会自动关闭，无需手动写finally

try (FileInputStream in = new FileInputStream("in.txt");
     FileOutputStream out = new FileOutputStream("out.txt")) {
    // 处理输入输出
}