JavaSE-IO流

// 查询指定目录下的指定文件
public class Main {
    public static void main(String[] args) throws IOException {
        searchFile(new File("D:/"), "a.txt");
    }

    public static void searchFile(File dir, String fileName) {
        // 判断dir是否是目录
        if (dir != null && dir.isDirectory()) {
            // 提取当前目录下的一级文件对象
            File[] files = dir.listFiles();
            // 判断是否存在一级文件对象，如果存在才能遍历
            if (files != null && files.length > 0) {
                for (File file : files) {
                    // 判断当前遍历的一级文件对象是文件还是目录
                    if (file.isFile()) {
                        // 如果是要找到的文件，把其路径输出即可
                        if (file.getName().contains(fileName)) {
                            System.out.println("找到了" + file.getAbsolutePath());
                        }
                    } else {
                        // 如果是文件夹，需要继续递归查找
                        searchFile(file, fileName);
                    }
                }
            }
        } else {
            System.out.println("对不起，当前搜索的位置不是文件夹！");
        }
    }
}

// 文件拷贝
String srcPath = "D:\\avatar.jpg";
String destPath = "D:\\new.jpg";
try (BufferedInputStream in = new BufferedInputStream(new FileInputStream(srcPath));
     BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(destPath));) {
    byte[] buffer = new byte[1024];
    int len = 0;
    while ((len = in.read(buffer)) != -1) {
        out.write(buffer, 0, len);
    }
    System.out.println("复制文件已完成~");
} catch (Exception e) {
    e.printStackTrace();
}

// 获取正确编码的输入流(InputStreamReader:将字节输入流转换为字符输入流)
String srcPath = "D:/a.txt";
try (Reader reader = new InputStreamReader(new FileInputStream(srcPath), "GBK");
     BufferedReader bufferedReader = new BufferedReader(reader);) {
    String line;
    while ((line = bufferedReader.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

// 输出正确编码的输出流(OutputStreamWriter:字节输出流转换为字符输出流)
String destPath = "D:/b.txt";
try (Writer writer = new OutputStreamWriter(new FileOutputStream(destPath), "GBK");
     BufferedWriter buffer = new BufferedWriter(writer);) {
    buffer.write("hello 不二橘子酱！");
} catch (IOException e) {
    e.printStackTrace();
}

@Data
public class Student implements Serializable {
    private String name;
    private transient String password;
    private int age;
}

// 序列化：把内存中的对象存入到磁盘文件中
Student s = new Student("不二橘子酱", "123456", 18);
try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("D:/a.txt"))) {
    // 直接调用序列化方法
    oos.writeObject(s);
} catch (IOException e) {
    e.printStackTrace();
}

// 反序列化：把磁盘中的对象数据转换成内存中的Java对象
try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream("D:/a.txt"))) {
    Student s = (Student) ois.readObject();
    System.out.println(s); // Student{name='不二橘子酱', password='null', age=18}
} catch (Exception e) {
    e.printStackTrace();
}

// 打印流:在打印数据功能上是一模一样的,区别在于PrintStream只能写字节数据;PrintWriter只能写字符数据
// PrintStream继承自OutputStream;PrintWriter继承自Writer
try (PrintStream ps1 = new PrintStream(new FileOutputStream("D:/a.txt"), true);
     PrintStream ps2 = new PrintStream("D:/b.txt");
     PrintWriter ps3 = new PrintWriter("D:/c.txt");
) {
    ps2.println("我是打印流输出的，是什么就打印什么");
    ps3.write("不二橘子酱");
} catch (Exception e) {
    e.printStackTrace();
}