IO简单示例

File类

用于对磁盘上的文件或目录进行操作

直接父类是Object

 

 

创建一个文件

public class FileTest {     public static void main(String[] args) throws IOException     {        File file = new File("C:/text.txt");               System.out.println(file.createNewFile());     } }

 

在一个目录下创建文件

public class FileTest2 {     public static void main(String[] args) throws IOException     {        File file = new File("C:/abc");               File file2 = new File(file,"hello.txt");               System.out.println(file2.createNewFile());               File file3 = new File(file,"xyz/world.txt");               System.out.println(file3.createNewFile());     } }

 

 

创建目录操作

public class FileTest3 {     public static void main(String[] args)     {        File file = new File("C:/abc/xyz/hello");               System.out.println(file.mkdirs());               System.out.println(file.isDirectory());     } }

 

 

列出指定目录下的文件或目录

public class FileTest4 {     public static void main(String[] args)     {        File file = new File("C:/java");               String[] names  = file.list();               for(String name: names)        {            System.out.println(name);        }               File[] files = file.listFiles();               for(File f : files)        {            System.out.println(f.getName());            System.out.println(f.getParent());        }     } }

 

 

文件删除操作

public class FileTest5 {     public static void main(String[] args) throws IOException     {        File file = new File("C:/abc/xyz/hello/text.txt");               //file.createNewFile();               boolean delete = file.delete();               System.out.println(delete);     } }

 

 

文件名过滤操作

public class FileTest6 {     public static void main(String[] args)     {        File file = new File("C:/java");               /*String[] names = file.list();               for(String name : names)        {            if(name.endsWith(".java"))            {               System.out.println(name);            }        }*/               String[] names = file.list(new FilenameFilter()        {            @Override            public boolean accept(File dir, String name)            {               if(name.endsWith(".java"))               {                   return true;               }               return false;            }        });               for(String name : names )        {            System.out.println(name);        }     } }

 

 

文件分隔符的使用

public class FileTest7 {     public static void main(String[] args) throws IOException     {        //不加盘符表示java安装的默认盘        File file = new File(File.separator + "helo.txt");               System.out.println(file.createNewFile());     } }

 

 

递归的使用（关键在于要先指定一个出口，才不会出现死循环）

public class Test1 {     public static int calc(int num)     {        if(num ==1 )            return 1;        else            return num * calc(num - 1);     }       public static void main(String[] args)     {        System.out.println(calc(5));     } }

 

 

斐波那契数列

public class Fabonaci {     public int calc(int pos)     {        if(1 == pos || 2 == pos)            return 1;        else            return calc(pos-1)+calc(pos-2);     }         private void sysout()     {        Fabonaci fab = new Fabonaci();        fab.calc(30);     } }

 

 

删除指定目录下的所有文件（用递归实现）

public class FileTest8 {     public static void deleteAll(File file)     {        if(file.isFile() || 0 == file.list().length)        {            file.delete();        }        else        {            File[] files = file.listFiles();                       for(File f : files)            {               deleteAll(f);               f.delete();            }        }     }         public static void main(String[] args)     {        File file = new File("C:/test");               try        {            deleteAll(file);        }        catch (Exception e)        {            // TODO Auto-generated catch block            e.printStackTrace();        }     } }

 

 

把指定目录下的文件结构以树的形式打印出来

public class FileTest9 {     // 判断目录或文件所在的层数     private static int times;       // 把目录下的文件以树结构的形式打印出来。     static void treeShow(File file)     {        if (file.isFile() || 0 == file.listFiles().length)        {            return;        }        else        {            File[] files = file.listFiles();              files = sortFile(files);              for (File f : files)            {               StringBuffer sb = new StringBuffer();                 if (f.isDirectory())               {                   sb.append(getTAbs(times));                   sb.append(f.getName());                   sb.append("\\");               }               else               {                   sb.append(getTAbs(times));                   sb.append(f.getName());               }                 System.out.println(sb);                 if (f.isDirectory())               {                   times++;                   treeShow(f);                   times--;               }            }        }     }       // 取得每个目录或文件所处层数的缩进     private static String getTAbs(int times)     {        StringBuffer sb = new StringBuffer();        for (int i = 0; i < times; i++)        {            sb.append("\t");        }          return sb.toString();     }       // 把目录下所有文件以目录为先的次序排序     private static File[] sortFile(File[] files)     {        List<File> list = new ArrayList<File>();        for (File f : files)        {            if (f.isDirectory())            {               list.add(f);            }        }        for (File f : files)        {            if (f.isFile())            {               list.add(f);            }        }          return list.toArray(new File[files.length]);     }       public static void main(String[] args)     {        File file = new File("C:/xdict");        treeShow(file);     } }

 

 

Stream类

 

从功能上分：输入流（InputStream）和输出流（OutputStream）

从结构上分：字节流(Byte Streams)和字符流(Character Streams)

 

字节流输入输出的基础是抽象类InputStream和OutputStream

字符流输入输出的基础是抽象类Reader和Writer

 

流的分类：

节点流：从特定的地方读写的流类。

过滤流：使用节点流作为输入或输出。过滤流是使用一个已存在的输入流或输出流连接创建的。

字节流的使用

 

FileInputStream类的使用

public class InputStreamTest {     public static void main(String[] args) throws Exception     {        InputStream is = new FileInputStream("c:/hello.txt");          byte[] buffer = new byte[200];          int length = 0;          if (-1 != (length = is.read(buffer, 0, 200)))        {            String str = new String(buffer, 0, length);            System.out.println(str);        }          is.close();     } }

 

FileOutputStream类的使用

public class OutputStreamTest {     public static void main(String[] args) throws IOException     {        OutputStream os = new FileOutputStream("c:/out.txt",true);               String str = "\nwelcomle";               byte[] buffer = str.getBytes();               os.write(buffer);               os.close();     } }

 

 

BufferedInputStream类，继承自FilterInputStream

 

 

BufferedOutputStream类，继承自FilterOutputStream

public class BufferedOutputStreamTest {     public static void main(String[] args) throws Exception     {        OutputStream os = new FileOutputStream("1.txt");               BufferedOutputStream bos = new BufferedOutputStream(os);               bos.write("http://www.sina.com.cn".getBytes());               bos.close();        os.close();     } }

 

 

ByteArrayInputStream类

public class ByteArrayInputStreamTest {     public static void main(String[] args) throws Exception     {        String str = "abcdef";               byte[] byteArr = str.getBytes();               ByteArrayInputStream bais = new ByteArrayInputStream(byteArr);               int c;               //一次只读一个字符        while(-1 != (c = bais.read()))        {            if(0==c)            {               System.out.println((char)c);            }            else            {               System.out.println(Character.toUpperCase((char) c));            }        }               bais.close();     } }

 

 

ByteArrayOutputStream类

public class ByteArrayOutputStreamTest {     public static void main(String[] args) throws Exception     {        String str = "hello world welcome";               byte[] arr = str.getBytes();               ByteArrayOutputStream baos = new ByteArrayOutputStream();               //把字节数组写入到字节数组输出流中        baos.write(arr);               //从字节数组输出流中得到字节数组        byte[] result = baos.toByteArray();               for(byte b : result)        {            System.out.println((char)b);        }               OutputStream os = new FileOutputStream("c:/test.txt");               //把字节数组写入到文件中。        baos.writeTo(os);               baos.close();        os.close();     } }

 

 

DataInputStream类，继承自FilterInputStream

 

 

DataOutputStream类，继承自FilterOutputStream

public class DataOutputStreamTest {     public static void main(String[] args) throws Exception     {        DataOutputStream dos = new DataOutputStream(new BufferedOutputStream(new FileOutputStream("data.txt")));               byte b = 3;        int i = 12;        char c = 'c';        float f = 0.3f;               dos.writeByte(b);        dos.writeInt(i);        dos.writeChar(c);        dos.writeFloat(f);               dos.close();               DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream("data.txt")));               System.out.println(dis.readByte());        System.out.println(dis.readInt());        System.out.println(dis.readChar());        System.out.println(dis.readFloat());               dis.close();     } }

 

 

自定义一个ByteArrayInputStream

public class MyOwnStream {     public static void main(String[] args) throws Exception     {        byte[] bytes = new byte[16];        for (int i = 0; i < bytes.length; i++)        {            bytes[i] = (byte) i;        }          MyInputStream myis = new MyInputStream(bytes);          int c = 0;        while (true)        {            if (-1 == (c = myis.read()))            {               break;            }            System.out.print(c + " ");        }          myis.close();     } }   // 这里使用了装饰者模式 class MyInputStream extends InputStream {     protected byte[] buffer;     protected int ptr = 0;       public MyInputStream(byte[] bytes)     {        buffer = bytes;     }       @Override     public int read() throws IOException     {        return (ptr < buffer.length) ? buffer[ptr++] : -1;     } }

 

重写InputStream类方法完整的例子

public class MyOwnStream2 extends InputStream {     protected byte[] data;     protected int ptr = 0;     protected int mark = 0;       public MyOwnStream2(byte[] bytes)     {        this.data = bytes;     }       @Override     public int read() throws IOException     {        return (ptr < data.length) ? data[ptr++] : -1;     }       @Override     public int read(byte[] b, int off, int len) throws IOException     {        if (ptr > data.length || len < 0)        {            return -1;        }        if ((ptr + len) > data.length)        {            len = data.length - ptr;        }        if (0 == len)        {            return 0;        }          System.arraycopy(data, ptr, b, off, len);        ptr += len;        return len;     }       @Override     public long skip(long n) throws IOException     {        return super.skip(n);     }       @Override     public int available() throws IOException     {        return data.length - ptr;     }       @Override     public void close() throws IOException     {        ptr = data.length;     }       @Override     public synchronized void mark(int readlimit)     {        this.mark = readlimit;     }       @Override     public synchronized void reset() throws IOException     {        if (mark > 0 || mark < data.length)        {            throw new IOException("The position is invalid.");        }          ptr = mark;     }       @Override     public boolean markSupported()     {        return true;     } }

 

 

字符流的使用

 

InputStreamReader

 

OutputStreamWrite

public class StreamTest {     public static void main(String[] args) throws Exception     {        FileOutputStream fos = new FileOutputStream("file.txt");          OutputStreamWriter osw = new OutputStreamWriter(fos);          BufferedWriter bw = new BufferedWriter(osw);          bw.write("http://www.google.com");        bw.write("\n");        bw.write("http://www.baidu.com");          bw.close();          FileInputStream fis = new FileInputStream("file.txt");          InputStreamReader isr = new InputStreamReader(fis);          BufferedReader br = new BufferedReader(isr);                 /*System.out.println(br.readLine());        System.out.println(br.readLine());        System.out.println(br.readLine());*/               String str = br.readLine();        while(null != str)        {            System.out.println(str);            str = br.readLine();        }          br.close();     } }

 

 

BufferedReader

public class StreamTest2 {     public static void main(String[] args) throws Exception     {        InputStreamReader isr = new InputStreamReader(System.in);               BufferedReader br = new BufferedReader(isr);               String str;               while(null != (str = br.readLine()))        {            System.out.println(str);        }               br.close();     } }

 

BufferedWrite

FileOutputStream fos = new FileOutputStream("file.txt");          OutputStreamWriter osw = new OutputStreamWriter(fos);          BufferedWriter bw = new BufferedWriter(osw);          bw.write("http://www.google.com");        bw.write("\n");        bw.write("http://www.baidu.com");          bw.close();

 

 

FileReader

public class FileReaderTest {     public static void main(String[] args) throws Exception     {        FileReader fr = new FileReader("src/com/anllin/io3/FileReaderTest.java");               BufferedReader br = new BufferedReader(fr);                String str ;        while(null != (str = br.readLine()))        {            System.out.println(str);        }               br.close();     } }

 

FileWriter

public class FileWriteTest {     public static void main(String[] args) throws Exception     {        String str = "hello world welcome nice bueaty";               char[] buffer = new char[str.length()];               str.getChars(0,str.length(),buffer,0);               FileWriter fr = new FileWriter("file2.txt");               fr.write(buffer);               fr.close();     } }

 

 

CharArrayReader

public class CharArrayReaderTest {     public static void main(String[] args) throws Exception     {        String str = "abcdefghijklmnopqrstuvwxyz";               char[] buffer = new char[str.length()];               str.getChars(0, str.length(),buffer,0);               CharArrayReader car = new CharArrayReader(buffer);               int i ;               while(-1 != (i = car.read()))        {            System.out.println((char)i);        }               car.close();     } }

 

 

字符集的分类：

ASCII     GB2312        GBK       Unicode         iso-8859- 1     UTF-8

public class CharsetTest {     public static void main(String[] args)     {        SortedMap<String,Charset> map = Charset.availableCharsets();               Set<String> set = map.keySet();               for(Iterator<String> iter = set.iterator(); iter.hasNext();)        {            System.out.println(iter.next());        }     } }

 

 

RandomAccessFile类，可以随机对文件进行读写操作。

public class RandomAccessFileTest {     public static void main(String[] args) throws Exception     {        Person p = new Person(1, "anllin", 170);          RandomAccessFile raf = new RandomAccessFile("person.txt", "rw");          p.write(raf);          raf.seek(0);//让读的位置回到文件的开头          Person p2 = new Person();          p2.read(raf);          System.out.println(p2.getId() + ", " + p2.getName() + ", "               + p2.getHeight());     } }   class Person {     int id;     String name;     double height;       public Person()     {       }       public Person(int id, String name, double height)     {        this.id = id;        this.name = name;        this.height = height;     }       public int getId()     {        return id;     }       public void setId(int id)     {        this.id = id;     }       public String getName()     {        return name;     }       public void setName(String name)     {        this.name = name;     }       public double getHeight()     {        return height;     }       public void setHeight(double height)     {        this.height = height;     }       public void write(RandomAccessFile raf) throws Exception     {        raf.writeInt(id);        raf.writeUTF(name);        raf.writeDouble(height);     }       public void read(RandomAccessFile raf) throws Exception     {        this.id = raf.readInt();        this.name = raf.readUTF();        this.height = raf.readDouble();     } }