Java中的IO整理

创建文件

public static void createNewFile() throws IOException {
        String fileName = "D:" + File.separator + "hello.txt";
        File f = new File(fileName);
        f.createNewFile();
    }

删除文件

public static void deleteFile() {
        String fileName = "D:" + File.separator + "hello.txt";
        File f = new File(fileName);
        if (f.exists()) {
            f.delete();
        }
    }

新建文件夹

public static void createNewDir() {
        String fileName = "F:" + File.separator + "ff";
        File f = new File(fileName);
        f.mkdir();
    }

递归遍历目录

public static void traversalDir(String filePath) {
        File dir = new File(filePath);
        File[] files = dir.listFiles();
        for (File file : files) {
            if (file != null) {
                if (file.isDirectory()) {
                    traversalDir(file.getAbsolutePath());
                } else {
                    System.out.println(file.getAbsolutePath());
                }
            }

        }
    }

写入文件

    public static void writeString2File() throws IOException {
        String filePath = "D:" + File.separator + "hello.txt";
        File f = new File(filePath);
        OutputStream out = new FileOutputStream(f, false);
        String str = "abcdefghijklmnopqs";
        byte[] bytes = str.getBytes();
        for (int i = 0; i < bytes.length; i++) {
            out.write(bytes[i]);
        }
        out.close();
    }

读文件

    public static void readFile() throws IOException {
        String filePath = "D:" + File.separator + "hello.txt";
        File f = new File(filePath);
        InputStream in = new FileInputStream(f);
        byte[] bytes = new byte[1024];
        int temp = 0;
        int count = 0;
        while ((temp = in.read()) != -1) {
            bytes[count++] = (byte) temp;
        }
        in.close();
        System.out.println(new String(bytes));
    }

对象序列化

    public class User implements Serializable{
    private static final long serialVersionUID = 1L;
    private transient int id = 123;
    private transient String name = "abc";
    private String password = "12345";

    public User(int id, String name, String password) {
        this.id = id;
        this.name = name;
        this.password = password;
    }

    public User() {

    }

    public int getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    private void privateMethod() {
        System.out.println("access the private method");
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", password='" + password + '\'' +
                '}';
        }
    }
    public static void serializClass() throws Exception {
        String filePath = "D:" + File.separator + "seri.txt";
        File f = new File(filePath);
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(f));
        out.writeObject(new User(123,"jim","abcde"));
        out.close();
    }

反序列化

    public static void deserializClass() throws Exception {
        String filePath = "D:" + File.separator + "seri.txt";
        File f = new File(filePath);
        ObjectInputStream in = new ObjectInputStream(new FileInputStream(f));
        User user = (User) in.readObject();
        in.close();
        System.out.println(user);
    }