IO流

2022-03-13 05:21:33

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();
        }
    }

码农公寓

File

字节流

缓冲流

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