IO流-白红宇

File

路径分隔符–File.pathSeparator

文件分隔符–File.seprarator

路径表示形式

path = “E://xp//test/2.jpg”
path =”E:”+File.separator+”xp”+File.separator….课跨平台的路径
path = “E:\xp\test\2.jpg”–>path = “E:/xp/test/2.jpg”(推荐的方式)

常用的方法：

getName()
getParent()返回上一级目录，没有上一级返回空
exists()文件是否存在
canRead()文件是否可读
isFile()
isDirectory() 判断
length()长度，字节数/文件夹无法读出长度
creatNewFile()创建文件(返回boolean类型)（若文件已经存在返回false）
delete()删除文件返回（boolean）
creatTempFile() 创建临时文件
deleteOnExit() 退出时自动删除
mkdir()创建目录，必须确保父目录存在
makirs()创建目录，递归创建目录。
String [] list()返回文件名称
File [] listFiles() 返回目录中的文件
listRoots() 根路径
FilenameFilter 过滤器

1 字节流：

输入流: InputStream ,read(byte[]),read(byte[],int off,int len),close()
FileInputStream()
输出流: OutputStream,write(byte[]),write(char [] ,int off,int len),flush(),close()
FileOutputStream()

2 字符流:

输入流: Reader read(char []) ,read(char [] ,int off,int len),close()
FileReader()
输出流: Writer write(char []),writer(char [] ,int off,int len),flush(),close()
FileWriter()

字节流

建立联系 File

选择流文件输入流

操作

关闭

// 读取文件    public static void main(String [] args){        File f = new File("D:/桌面/a.txt");        byte [] file = new byte[1024];        InputStream in = null;        try {            in = new FileInputStream(f);            int len = 0;            while(-1 != (len = in.read(file))){                String s = new String(file, 0, len);                System.out.print(s);            }        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally {            try {                if (in!=null)                in.close();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }    }

建立联系 File

选择流文件输出流 OutputStream FileOutputStream

操作 write() flush()

关闭

OutputStream 将数据写入到文件中，FileOutputStream将数据写入到流中
InputStream 将数据从文件中读取，FileInputStream将从六中读取数据
FileOutputStream(File , true)将数据追加到文件中，默认为false
**一定一定一定要记得关闭流***

//写入到文件    public static void main(String [] args){        File file = new File("D:/桌面/b.txt");        OutputStream out = null;        try {            out = new FileOutputStream(file,false);            String s = "写入文件操作\r\n";            byte []  s2 = s.getBytes();            out.write(s2);        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally{            if (out!=null){                try {                    out.close();                } catch (IOException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }            }        }    }

//复制文件    public static void main (String [] args){        File file1 = new File("D:/桌面/tree.jpg");        File file2 = new File("D:/桌面/trees.jpg");        InputStream input = null;        OutputStream output = null;        try {            input = new FileInputStream(file1);            output = new FileOutputStream(file2);            byte [] data = new byte [1024*4];            int len = 0;            while(-1 != (len = input.read(data))){                output.write(data,0, len);                System.out.println(data);            }        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();            System.out.println("没有找到文件");        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally{            try {                output.close();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }            try {                input.close();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }            System.out.println("写入成功");        }    }

字符流:只能处理纯文本.txt .html

Writer FileWriter

Reader FileReader

1 建立联系

2 选择流 Writer FileWriter

3 读取char[] dlush

4 关闭

FileWriter(File ,true) 追加
append()追加

//FileReader 读取文件public class testFileReader {    public static void main (String  []  args){        File file = new File("D:/桌面/switch.txt");        File file2 = new File("D:/桌面/switch2.txt");        Reader input = null;        Writer output = null;        try {            input = new FileReader(file);            char [] data = new char [1024];            int len = 0;            while (-1 != (len = input.read(data))){                String s = new String(data, 0, len);                System.out.println(s);            }        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();            System.out.println("文件读取失败");        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally{            try {                input.close();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();                System.out.println("关闭失败");            }        }    }}

//FileWriter复制文件public class testFileReader {    public static void main (String  []  args){        File file = new File("D:/桌面/switch.txt");        File file2 = new File("D:/桌面/switch2.txt");        Reader input = null;        Writer output = null;        try {            input = new FileReader(file);            output = new FileWriter(file2);            char [] data = new char [1024];            int len = 0;            while (-1 != (len = input.read(data))){                String s = new String(data, 0, len);                output.write(s);    //          System.out.println(s);            }        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();            System.out.println("文件读取失败");        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally{            try {                input.close();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();                System.out.println("关闭失败");            }            try {                output.close();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();                System.out.println("关闭输出流失败");            }        }    }}

缓冲流

1，字节缓冲流

BufferedInputStream
BufferedOutputStream

2,字符缓冲流

BufferedReader ReadLine()
BufferedWriter newLine()换行
字节流文件拷贝+缓冲流，提高性能
缓冲流(节点流)
//使用新增方法不能发生多态

//用BufferedReader包装        BufferedReader input = null;        BufferedWriter output = null;        try {            input = new BufferedReader(new FileReader(file));            output = new BufferedWriter(new FileWriter(file2));            String temp ;            while(null != (temp = input.readLine())){                System.out.println(temp);            }。。。。。。//输出方式同理，writer（String s ）

转换流：字节流转字符流处理乱码（编码集、解码集）

String(byte [] bytes,Charset charset) 使用charset编码来编码byte数组
String(byte [] bytes,int offset, int length,Charset charset) 编码byte数组的子数组
getbytes()使用默认的编码方式返回字节数组
getBytes(Charset charset)使用指定的编码方式返回字节数组

//处理文件编码    public static void main (String [] args) throws UnsupportedEncodingException{        String str1 = "字符串";        byte [] data = str1.getBytes("utf-8");        String str2 = new String(data, "utf-8");        System.out.println(str2);    }

字节转为字符:（转换流）

InputStreamReader()

OutputStreamWriter()

//InputStreamReader(new FileInputStream(new File()))

//字节流转字符流    public static void main (String [] args) throws IOException{        File file1 = new File("D:/桌面/1.txt");        File file2 = new File("D:/桌面/2.txt");        try {            BufferedReader input = new BufferedReader(                    new InputStreamReader(                            new FileInputStream(file1),"utf-8")                    );            String len ;            while (null != (len = input.readLine())){                System.out.println(len);            }        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }