Java IO文件流

创建文件

//add file       File file =new File("E:\\java用文件","file.txt");       try{           file.createNewFile();           System.out.println("creat ok!");       }       catch (IOException e){           System.out.println("creat go die!");           e.printStackTrace();       }

 删除文件

//deletefile.delete();

读取文件数据

//way firstFile file =new File("E:\\java用文件","file.txt");                InputStream input = null;                byte b[] = new byte[(int)file.lenght()];                                            //根据文件的大小定义数组空间                try {                    input = new FileInputStream(file);                    input.read(b);                    input.close();                }catch (IOException ee){                    ee.printStackTrace();                }//way second    常用File file =new File("E:\\java用文件","file.txt");                InputStream input = null;                byte b[] = new byte[(int)file.length()];                int temp = 0;                int len = 0;                try{                    input = new FileInputStream(file);                                 //使用FileInputStream为InputStream实例化                    while((temp = input.read())!= -1)                    {            //使用while循环读取文件内容，到达结尾是temp=-1                        b[len] = (byte)temp;                        len++;                    }                    input.close();        //关闭输入流                }catch(IOException ex){   //捕捉异常                    ex.printStackTrace();                }                System.out.println(new String(b));

向文件写入内容

//会覆盖文件原本内容File file =new File("E:\\java用文件","file.txt");                OutputStream out = null;        //声明 OutputStream对象                String str = "Hello";                byte b[] = str.getBytes();      //把字符串转换为b数组                try{                    out = new FileOutputStream(file);                                               //用 FileOutputStream实例化OutputStream                    out.write(b);              //写入数据                    out.close();               //关闭输出流                    System.out.println("write ok!");                }catch (IOException ev){       //捕捉异常                    System.out.print("write go die!");                    ev.printStackTrace();      //打印异常                }//在末尾追加内容//将传入FileOutputStream 构造方法中的参数append赋值为true即可//public FileOutputStream(File dile,boolean append)throws//FileNotFoundException File file =new File("E:\\java用文件","file.txt");                OutputStream out = null;        //声明 OutputStream对象                String str = "Hello";                byte b[] = str.getBytes();      //把字符串转换为b数组                try{                    out = new FileOutputStream(file,true);                                               //用 FileOutputStream实例化OutputStream，添加true！！！                    out.write(b);              //写入数据                    out.close();               //关闭输出流                    System.out.println("write ok!");                }catch (IOException ev){       //捕捉异常                    System.out.print("write go die!");                    ev.printStackTrace();      //打印异常                }//若想换行，可以在需要换行的字符串处添加转义字符"\r\n"即可

字符流

读取文件内容

File file =new File("E:\\java用文件","file.txt");                Reader read = null;       //声明Reader对象                char c[] = new char[(int)file.length()];                try                {                    read = new FileReader(file);    //使用FileReader实例化Reader                    read.read(c);                    read.close();                }catch (IOException ee){                    System.out.println("read go die !");                    ee.printStackTrace();                }                System.out.println(c);

使用while方法读取

   

 File file =new File("E:\\java用文件","file.txt");                Reader read = null;       //声明Reader对象                char c[] = new char[(int)file.length()];                int temp = 0;                int len = 0;                try                {                    read = new FileReader(file);    //使用FileReader实例化Reader                    while((temp = read.read())!=-1)                    {                     //用while读取 到达结尾时temp = -1                        c[len] = (char)temp;                         len++;                    }                    read.close();                }catch (IOException ee){                    System.out.println("read go die !");                    ee.printStackTrace();                }                System.out.println(c);

写入

//way1File file =new File("E:\\java用文件","file.txt");                Writer out = null;                String str = "lllllll\r\n";                char c[] = str.toCharArray();                try{                    out = new FileWriter(file,true);                    out.write(c);                    out.close();                    System.out.println("write  ok!");                }catch (IOException ee) {                    System.out.print("write  go die!");                    ee.printStackTrace();                }//way2File file =new File("E:\\java用文件","file.txt");                Writer out = null;                String str = "lllllll\r\n";                try{                    out = new FileWriter(file,true);                    out.write(str);                    out.close();                    System.out.println("write  ok!");                }catch (IOException ee) {                    System.out.print("write  go die!");                    ee.printStackTrace();                }

字节流

字节输入流

   

File file = new File ("E:\\java用文件","file.txt");                InputStream input = null;    //声明InputStream对象                byte b[]=new byte[(int)file.length()];                int temp = 0;                int len = 0;                try{                    input = new FileInputStream(file);                                      //使用FileInputStream为  InputStream实例化                    while((temp=input.read())!=-1)                    {                        b[len]=(byte)temp;                        len++;                    }                    input.close();                }catch(IOException eq){                    eq.printStackTrace();                }                System.out.println(new String(b));

字节输出流

 

File file = new File ("E:\\java用文件","file.txt");                OutputStream out = null;                String str = "el psy congroo";                byte b[] = str.getBytes();                try{                    out = new FileOutputStream(file,true);                    out.write(b);                    out.close();                    System.out.println("write   ok!!!");                }catch(IOException ew){                    ew.printStackTrace();                    System.out.println("write go die");                }

对象序列化

对象序列化是将对象状态转换为可保持或传输的格式的过程

若需要某个对象能支持序列化机制，必须实现Serializable接口

class student implements Serializable{    String number;    String name;    String sex;    String birthday;    String department;    public student(String number,String name,String sex,String birthday,String department){        this.number = number;        this.name = name;        this.sex = sex;        this.birthday = birthday;        this.department = department;    }}

对象输出流

File file =new File("E:\\java用文件","file.txt");                String name = jtname.getText();                String number = jtnumber.getText();                String sex = jtsex.getText();                String birthday = jtbirthday.getText();                String department = jtdepartment.getText();                student stu = new student(number,name,sex,birthday,department);                FileOutputStream fout = null;                ObjectOutputStream oos = null;                try{                    fout = new FileOutputStream(file,true);  //实例化文件输出流                    oos = new ObjectOutputStream(fout);      //实例化对象输出流                    oos.writeObject(stu);                    //把对象写入输出流                    oos.close();                             //关闭对象输出流                }catch (IOException er){                    er.printStackTrace();                    System.out.println("writeobject go die");                }

对象输入流

File file =new File("E:\\java用文件","file.txt");                FileInputStream fis = null;                ObjectInputStream ois = null;                try{                    fis = new FileInputStream(file);                    ois = new ObjectInputStream(fis);                    student stu = (student)ois.readObject();   //读取stu对象需要强制转换                    ois.close();                    jname.setText(stu.name);                    jsex.setText(stu.sex);                    jbirthday.setText(stu.birthday);                    jdepartment.setText(stu.department);                }catch (IOException ex){     //捕捉IOException异常                    ex.printStackTrace();                }catch(ClassNotFoundException we){    //捕捉ClassNotFoundException异常                    we.printStackTrace();                }